Metrology for the cabinetmaker

[Brian Holcombe]

Wanting to spur a bit of discussion, I wrote up this post and I'm curious to see if it is of any use.



Metrology for the Cabinetmaker – Introduction

This post is intended as the beginning of a conversation on inspection equipment and measurement standards rather than a conclusive how-to. My equipment, techniques and process are in a continuous evolution. These techniques have been working effectively for me and so I have decided to share them, however the I do not run a metrology lab, I run a wood shop, so be aware that these techniques may be incorrect or incomplete. I introduce this only to encourage thought and spark further discussion.

The reader may wonder as to why fine measurements make any difference at all in a wood shop. After all, wood moves with change in relative humidity and so one may conclude that minor gaps are inevitable. Wood movement is one of the greater challenges of woodworking and yet we can plan for it and build accordingly, engineering considerations for wood movement into our product.

As example, looking at the typical mortise and tenon joint. Wood moves across the grain, so if the mortise were cut in the typical fashion it would shrink and swell across the width. At the point of production it may be .500″ wide, and months later it may be .510″ wide. The tenon, if produced from the same batch of material in the same grain orientation at the same time will have moved in the same fashion, so it too will have moved from .500″ wide to .510″ wide maintaining the fit between parts. Along the height of the board it will gap at the top and bottom of the mortise. This can be partially countered by lightly compressing the wood during the fitting process. The joint can draw-bored to retain it tight against the tenon shoulder and the joint can be fully shouldered joint to hide the potential gaps created at top and bottom of the tenon that are not solved by compression.

Gaps are also created by errors in setup and cutout. These are due to a host of circumstances including layout error, machine setup error, and tool bit deflection. Repair of these unexpected circumstances often requires custom fitting, remaking of parts or other time consuming approaches to repair or otherwise alleviate this circumstance. To avoid minor gaps an in consistencies created by these errors the first step is to remove uncertainty where we can find it. This requires a level of precision counted in thousandths of an inch for our machinery setup. Good technique combined with accurate equipment helps to produce accurate results, as example a saw that cuts squarely can also be used to make accurate length parts as both sides of the part can be make the same length. Accuracy is an important component in efficiency of process and it begins with the checking tools themselves before they are used to inspect the equipment or work piece.

Knowing that a square is actually square and that 12″ is actually 12″ is a worthwhile venture when the goal is efficiency. These questions become increasingly difficult to answer without the proper equipment and so it is for this reason that I feel the woodshop benefits from having a basic kit of highly accurate tools used as standards for inspection. This kit is commonly referred to as a metrology kit in the machine shop.

Metrology is the scientific study of measurements with an aim to create a common understanding and agreement of units. This agreement allows the industrialized world to create products with confidence that parts from independent sources will interact properly. For this reason many have adopted the metric system, a system of standards based on realizable values, as their countries have industrialized. If not directly replacing their own systems many countries have standardized their systems of measure on the metric system. As example, the standard for a foot (Imperial) is exactly 30.48 cm, the shaku (Japan) is 30.3cm and the chi (China) is 32cm.

Modern standards which create the basic building blocks of the metric system are derived from specific references which remain constant. As example, a meter is the length of the path travelled by light in a vacuum during a time interval of 1/299792458 of a second. These such references form the primary standards upon which international systems base their physical standards. In the US these standards are maintained by NIST. Quality measuring tools are calibrated to NIST standards and certain forms of work require periodically recalibrating tools to those standards.

In the woodshop we can compare a part to the space it must consume, mark and cut, or we can measure the space and build the part using that measurement as a reference, neither operation requires an international standard. However, if our work involves using multiple tools, each reliant upon a consistent series of measurements then we are best served by forming a shop standard and that shop standard may as well be derived from the international standards.

In a practical sense one need only compare two tape measures to realize that a lack of standards can complicate things quite rapidly. If you’re using a few different steel rules and a set of digital calipers then it’s best if they all agree with one another. This is further complicated when the machinery itself has built in gauges and those gauges are relied upon. Consistency in measuring devices is helpful in avoiding transfer errors.

Below I will detail a few of the measuring devices which are useful in the workshop, both highly accurate tools and moderate or low accuracy tools. They’re all necessary at times and their varying degree of accuracy or simplicity each make them useful in different ways.

Please note that in machine shop’s which utilize imperial measurements, the basic unit of measure is one thousandth of an inch (.001″), commonly referred to as a thousandth, or ‘a thou’. So, for example .500″ would be read out-loud as ‘five-hundred thousandths’. Finer than a thousandth is a ten-thousandth of an inch, or ‘a tenth’, this is confusing to many as a tenth is .100″, but the tenth as commonly referenced in a machine shop is one ‘tenth’ of a thousandth or .0001″. Still, it would be unusual to call out .5001″ as five-thousand and one tenths, instead it would be referred to as ‘a tenth over five hundred thou’ or similarly clear way of providing that it is not dead on .500″ but a tenth over.

Surfaces

In precise measuring, life begins with the surface plate. A surface plate is a true flat surface, often to a degree of precision measured in tenth thousandths of an inch (shop grade) or hundredth thousandths (Laboratory grade). These plates are calibrated by differential electronic level and are lapped flat, this plate arrived with the readout provided by the manufacturer. This surface is the basis for most comparative measuring so an accurate plate is a nice thing to have and fairly inexpensive.

The surface plate, along with all of the other precision tools are covered when not in use.
Click image for larger version. 413891

Immediately following the surface plate are the straight edges. The straight edge is a crucial piece of equipment in the workshop. This simple device allows the ability to compare surfaces to a known true reference. There are many types of straight edges, shown here is a beveled edge straight edge purpose built for checking plane soles.

Taking little for granted, I have checked this straight edge for flatness and parallelism. The process is done by applying marking compound to the surface plate then taking an imprint of the edge. I followed that by taking a sweep over the straight edge with an indicator in search of errors.

Straight edges must be supported along their length when they are stored, or they can be stored flat in a toolbox so long as they’re protected from other objects banging into them.
Click image for larger version. 413892

Another type of straight edge, the camel back. Rather than being ground flat, these are sometimes scraped by hand. This one in particular scraped by a very talented operator, by hand. This device is accurate to a few tenth-thousandths of an inch.
Click image for larger version. 413893

Specific to woodworking are winding sticks, wooden sticks used to define twist or ‘wind’ (think wind like a watch, not like the weather). These are used to give a basic understanding of surface defects. These are compared to the surface plate to ensure that they read accurately.
Click image for larger version. 413894

Angularity

The angles referenced most often in a typical woodshop are 90 degrees and 45 degrees. To check 90 degrees a tool know as an angle block can be used. These plates are best accurately scraped flat on their surfaces, square about their main faces and the edges square to the main faces and also flat. They can be used in conjunction with one another for comparing a square surface on three faces at one time.
Click image for larger version. 413895

Next up is the master square, this square is a precision ground engineer’s square certified to a high degree of angular accuracy. This is an A grade Mitutoyo square, which agrees with the angle plates above. This is mainly used for comparison with other squares and occasionally brought to the work but it is never scribed against.
Click image for larger version. 413896

A multitude of squares can be utilized in the workshop including various sizes and calibrations of try squares intended for checking work and creating layouts. Next is a smaller master square, made by Starrett, that is inspected accurate to .0001″ and it agrees with my angle plates.
Click image for larger version. 413897

Finally, I have another precision square which is of a quality that can be scribed against and used for other similar tasks without much concern. It is highly accurate, but it is the one square in the shop that I will retune periodically to ensure it remains accurate.

Angular measurements outside of 90 degrees, are read and transferred in variety of ways depending on the degree of precision required. Measurements can be provided by protractor, angle blocks, fixed angles or sine bars. The most basic measurement kit is shown here; a bevel gauge which is used to compare and transfer angles and a simple protractor. A high quality bevel gauge can be quite reliable and this example, made by Chris Vesper has proven highly reliable.
Click image for larger version. 413898

For the rest of the article see Page 2 (https://sawmillcreek.org/showthread.php?275871-Metrology-for-the-cabinetmaker)

[Robert Engel]

I think with the advent of CNC is so many shops "milling" wood has taken on a completely new meaning.

But my method of work for ww'ing is more related to consistency than accuracy.

A few example:

I'm not as interested in the absolute length of a board as I am that certain parts are exact same length. So my method of work is "measure once, cut X times" using a stop block.

Or that an angle is not necessarily exactly a particular degree, but rather close within a range of error, and the matching angle is dialed in to be complementary.

Or while flatness is crucial for a lapping plate, its not the same for a table top.

That said, precision is necessary for accurate machine set up.

Which got me to wondering - is there a difference between accuracy and precision so I looked them up.

Accuracy: "the degree to which the result of a measurement, calculation, or specification conforms to the correct value or a standard".

Precision: "the quality, condition, or fact of being exact and accurate"

Well that sure cleared things up LOL.

[Bill Dufour]

To my mind accuracy is not really needed. What we need is repeatability. Tests have shown the harbor freight digital calipers are actually very accurate. Most of them are good enough for metal working and all are good enough for wood where 0.0001 accuracy is not needed since 0.001 is plenty good enough for wood.

Accuracy: "the degree to which the result of a measurement, calculation, or specification conforms to the correct value or a standard".

Precision: "the quality, condition, or fact of being exact and accurate"

Well that sure cleared things up LOL.[/QUOTE]

[Brian Holcombe]

I think with the advent of CNC is so many shops "milling" wood has taken on a completely new meaning.

But my method of work for ww'ing is more related to consistency than accuracy.

A few example:

I'm not as interested in the absolute length of a board as I am that certain parts are exact same length. So my method of work is "measure once, cut X times" using a stop block.

Or that an angle is not necessarily exactly a particular degree, but rather close within a range of error, and the matching angle is dialed in to be complementary.

Or while flatness is crucial for a lapping plate, its not the same for a table top.

That said, precision is necessary for accurate machine set up.

Which got me to wondering - is there a difference between accuracy and precision so I looked them up.

Accuracy: "the degree to which the result of a measurement, calculation, or specification conforms to the correct value or a standard".

Precision: "the quality, condition, or fact of being exact and accurate"

Well that sure cleared things up LOL.

Thanks for the detailed reply. I believe the mathematical description of precision is along the lines of your description of consistency. Ideally both have practical limitations depending on their application and material and both have application.

As I understand it, accuracy can be practically defined as to how close your reading is to the actual number. What 2" is actually and how it compares to what you define as 2" and how close they are is accuracy.

Precision is how similar things are, so in a production run, I'm precise if all of my parts are within my range of tolerance, I'm imprecise if they fall out of that range.

You're using good practice and I certainly agree with your approach. I'm suggesting to augment good practice with accurate measuring, because there is an expediency found in accuracy.

Take your example of a saw cutting to a stop block. If the blade is not square, then the parts may be different sizes when you're finished, because as you flip the parts you're cutting a trapezoid rather than a rectangle. If you're doing it without paying very close attention to the error (good practice) than some parts will be trapezoids and some will be parallelograms.

What I'm pursuant of is, is the ability to get the error small enough that it doesn't have a meaningful effect, such that when cutting large quantities of parts I can have the error small enough that I dont need to pay strict attention to orientation from very early on through to the end of the process. IE I want interchangeable parts in large quantity rather than specific parts, and I want to still retain 100% of the quality that is provided when each part is hand fitted.

This is unlikely to ever occur in my work, but it's nice to greatly reduce the amount of hand fitting which is seriously time consuming and brings little value over cutting precisely the first time.

[Brian Holcombe]

To my mind accuracy is not really needed. What we need is repeatability. Tests have shown the harbor freight digital calipers are actually very accurate. Most of them are good enough for metal working and all are good enough for wood where 0.0001 accuracy is not needed since 0.001 is plenty good enough for wood.

Accuracy: "the degree to which the result of a measurement, calculation, or specification conforms to the correct value or a standard".

Precision: "the quality, condition, or fact of being exact and accurate"

Well that sure cleared things up LOL.

Personally, I prefer to buy good once. I have one set of inexpensive calipers, a few years old, floating around the garage and the head is beginning to die, it gives weird errors at random and so it's going to find it's way out the window one day. I've had a set of mitutoyo calipers for 20 years that still measure accurate.

[Dan Friedrichs]

I'm going to go out on a limb, here, and say that I think you have a small preference for Mitutoyo instruments :)

I assume you acquired some of those instruments used, and obviously people mark their tools, but it's still slightly disconcerting to see my somewhat-unusually-spelled last name on your comparator stand! :D

I enjoyed the post very much, and am looking forward to the next installment! If I could take the liberty of trying to summarize your broader point, I think you're saying that: given the right tools and techniques, you can achieve hand-fitted-quality in less time, and gain the advantage of interchangeability and repeatability.

Thanks for writing this up and sharing!

[andrew whicker]

Your measurement tools compete against professional high quality machine shops. I work in a high end machining environment and we use many of these tools. Some of our work requires .0001" discretion.

In our case, if we want true accuracy we go into a CMM room. This room is kept at 70 F. For metal, the humidity isn't important as far as I'm aware. The part should be left overnight if it is really critical. All measurement tools stay in that room. I guess what I'm trying to say is that your measurements will change overnight with wood unless you are in a conditioned air location. I don't have conditioned air, but luckily live in a desert.

I agree with your approach and I am investing in better measuring equipment over time. Hand fitting is a huge waste of time and I also don't find it acceptable practice to just "expect handwork". For my cut off saw, I use a Bosch miter saw. I take a machinist square and set it to the blade so that there is no light. However, the blade most definitely deflects. I think this must be the reason behind saws like the upcut saw. Big diameter blade and I'm assuming it is thicker too. Bigger Arbor probably with bigger motor shaft bearings, etc. It's interesting seeing the difference in accuracy between commercial and residential.

A next step for me is to get a 3 phase converter to get into the commercial tooling space. I've also been eyeing knee mills for help with woodworking and fab'ing.

[michael langman]

There is much that can be discussed in trying to achieve accuracy in producing things that have many parts.
While working with wood is not usually considered something that requires the extremes of accuracy that you are referring to in using tenth indicators and surface plates, gage blocks etc., there are certain areas of production that would benefit you in producing accurate parts in a production type atmosphere.

Having accurate jigs and fixtures, accurate machine setup, blueprints of parts and assemblies that use geometrical tolerancing, so as to determine the correct datums to work off, of and the degree of accuracy needed in that particular aspect of that part are all important aspects of manufacturing something. Experience and technique are also big factors.

One can only be as good, as what they have been exposed to, and learned from that exposure. That is why apprenticeships are so important in producing excellent craftsman. And why so many are drawn to places like this website.

How far one wishes to delve into this area in wood working is questionable, but I guess interesting, if you are into that sort of thing. :)

Mark Duginsky made a good point in his you tube video on machine setup in the wood shop. Basically it was to the point that a good straight edge, square,jigs and fixtures, and using paper as shims to achieve accurate adjustments in producing good parts was all one really needed to make accurate things in the wood shop.

[andy bessette]

So well done and excellent photos. Bravo!

I especially like the sliding T-bevel and protractor.

[Prashun Patel]

Personally, such accuracy and precision is beyond my needs; but I'm a hobbyist woodworker with the luxury of time to sneak up on fits or creatively design around errors. I think the salient point in his whole article is seeking efficiency. Once you know your ability to measure is perfect, it becomes possible to design completely by math. Anything less requires you to add some element of human judgment to the equation, and possibly recalibration/recalculation along the way.

[Robert Engel]

Take your example of a saw cutting to a stop block. If the blade is not square, then the parts may be different sizes when you're finished, because as you flip the parts you're cutting a trapezoid rather than a rectangle. If you're doing it without paying very close attention to the error (good practice) than some parts will be trapezoids and some will be parallelograms.
Yes, that is why I said it is different with one's machines. The need to be dialed in as accurately as possible.

Thanks for the excellent distinction between "accuracy" and "precision".

This precisely explains why cutting a whole bunch of parts consistently, but to an inaccurate size proves it all goes back to the dark matter (what used to be my gray matter).

:D

[Jim Becker]

Excellent writing, Brian!

[Mark Bolton]

Im with Bill and Dan they locked it down out of the gate. The need for extreme precision either comes from ones internal neuroscies or the financial need for production and repeatability. For years I argued about people being too fussy with thousandths in woodworking. Until we move the shop into the CNC world. Now they mean everything. They mean a job going together smoothly or perhaps painfully, or perhaps not at all. The thousandths will always matter to the neurotic (which CNC will turn you into, trust me, I know). I believe there is still zero need for thousandths for the person making on a creative level. Those thousandths are dealt with in their hands, feel, fit, and can be on one side or the other and still come out with a phenomenal result.

This chase for "metrology" in wood, to me, comes from a sycophancia with the youtube metal working world. The Tom Liptons, Stephan Gotswinters, Robin Renzettis, all of which I salivate for their next videos yet settle for lowly instagram posts. While they drive for millionths because its a passion, I dont think any of them would pursue it if there weren't a profitable income from it. They are producing parts to a spec'. Peter Stanton makes parts to a spec'. He makes a swivel hose replacement to a lesser spec though still higher than we are capable of because its done in his sleep.

Woodworking requires this only if you need it to satisfy your neurosis OR to satisfy having a bunch of inconsistent parts be able to be assembled by, anyone.

Either is fine.

[Bill Dufour]

I rmember reading years ago that the human eye can look at a plane surface and tell if two parts, fitted together to make that plane, are off by 1/1000 of an inch. Of course hit it with a fine piece of sandpaper and that glue line is gone from sight.
I find it is easier to provide slight setbacks so it is obvious the two surfaces are not supposed to be co-planer. Such as when legs meet a table apron I set the apron back 1/8 " If I get it wrong by 1/000 no one can tell. Same idea with a raised panel door I set the panel below flush or proud of flush by 1/4 -1/16"
Bill D

[Mark Hennebury]

This is where you really get to know people.

[Brian Holcombe]

Thanks gents, I appreciate the many comments on this thread. Really enjoyable to have a good discussion going.

[Brian Holcombe]

I wanted to touch on a few things, my background prior to woodworking was working at a machine shop. At the shop I was taught how to read mics, use snap gauges, dial bore gauge etc. After a while it becomes second nature and it's a speedy process. Putting calipers on a tenon doesn't take me very long at all. I have experience that stems from a machine shop so I tend to solve things in a machinist fashion when dealing with machine tools.

I had a few problems to solve that had really been creating annoying issues in my work, the most important of which was tooling height. For the Maka especially, the hollow chisel less so and the router much less so the height of the cutter is critical. I like to work off of a centerline for much of what I do and being on center is not the easiest thing to judge by knife lines. The Maka really brought this home because the tooling can't be easily brought up to the part and matched by eye.

The second was cutting squarely with both the table saw and chop saw. It becomes very easy to see wether or not a board is cut squarely when you can put an 18" grade A square on the corner and see plainly wether or not it's square (so long as your sides are flat). Cutting exact lengths is not quite as critical, but it does come up at times.

I build things like benches that have a stretcher spanning the distance and if the end boards are not exactly parallel to one another than the joints will gap at opposite sides. Actually it is that particular project which has caused me to ramp up the level of precision. There is no space to make up for a screw up, if I position something .010" off I will see a gap. If I cut a mortise oversize, I see it. It's a simple project, but it only looks good with very tight neatly made joinery. I cut the boards square then transfer them to the Bridgeport Knee mill for mortising. Very easy thing to do if your table saw cuts very squarely.

Precision tends to build on itself, if every tool is working within a tight tolerance then the work is fast and accurate, so I work toward getting everything within a narrow range and keep a close eye on things bettering them as I can afford to. Then when I work with CNC people like Jim Becker, it makes it easy because we're speaking the same language and I can provide very accurate parts for him to work off of.

When I worked mostly by hand I did not mind if every part was slightly different, but with many machines being relied upon my tolerance for variance is much much lower.

Certainly one begins to realize pretty quickly that wood provides a wider range of acceptable tolerance than say machining metal for a shrink fit, but the range can be understood and worked around effectively. I know when I run a large batch of tenons that I'm going to have a range of acceptable tolerance of .005". Fussiness can be avoided by understanding acceptable tolerance ranges and how to move the range to a point at which the parts work well, can be matched during final assembly or will simply have a snug fit/light fit that is within the tolerance of the glue being used.

The way I interpret something as being fussy is to mean that it is too time consuming. Certainly it is much easier to fuss over the first fit, then make the run and they all fit exactly as planned. It's much less fussy than messaging every mortise/tenon.

[Mike Cutler]

Brian

Nice article. Very well written.
Early in my career I worked in a mechanical standards lab, calibrating virtually every tool a machinist might ever need, so I also am a little biased to the need for quality measuring devices. I cannot imagine doing machine setups without quality measuring devices.
William Ng's Five cut method for squaring a fence is absolutely brilliant, but my large precision triangle has it square before the first test cut. Yeah, it cost a pretty penny, but now it doesn't take me a 1/2 hour to set my slider up any longer
It is true that the wood you cut today will be a different dimension tomorrow, but quality work,is still quality work.

[Jim Becker]

The bottom line for me is that ... nothing bad will ever come from having accurate measuring tools and methods, regardless of the material. The same goes for actually fitting components together based on the components themselves, rather than "measuring" and hoping something will fit on any given day, particularly with wood. The more accurate the setup of stationary tools is, the more consistent we can be, whether we are getting it right or making the same mistake over and over. :D

[Mark Bolton]

nothing bad will ever come from having accurate measuring tools and methods, regardless of the material.

That is until you come in contact with someone who becomes so obsessed with overly unnecessary accuracy, details, design, whatever, that they either never actually make anything because they are always working on those details, or they are never satisfied with anything they make because of obsessing with those details.

These conversations always remind me of a short stint having a full time pottery studio. There were several local potters in the area and we would all meet monthly to just talk about what we were working on. A couple in this group were very structured "artists" who had MFA's in ceramics, some others were individuals who had completed hugely in-depth full time 2 year programs in ceramics. Several of these people had simply educated themselves out of the ability to make a bowl, or a mug, the proportions were always wrong, clay body wasnt just so, glaze, on and on. They would never be happy, or furthermore profitable (they pursued this for a career path). Their pursuit of perceived perfection consumed all the time they had available to either enjoy their craft, or put food on their table which are the only two motivations to do any of this. Its either a hobby you want to enjoy, or a means to pay your bills. Of course your hobby may diverge into millionths level accuracy in the flatness of your cast iron table saw top, so I guess that works too.

Fussing over the details is great, until it isnt great anymore.

[andy bessette]

...my background prior to woodworking was working at a machine shop...

Prior to woodworking and boat building my background was design engineering. And only in my 70's did I finally pickup a couple machines I had long desired: an ancient knee mill and metal lathe to teach myself machining. Attached are photos of the first part I made (mostly on the mill) a boom end fitting for a sailboat. The metrology is still a work in progress.

https://i.postimg.cc/mDhRkwfj/boom-end-1.jpg (https://postimages.org/)
https://i.postimg.cc/G298RGMw/boom-end-2.jpg (https://postimages.org/)

[Mark Bolton]

That is some in-sane level manual machining for a lathe and knee mill. Super nice

[andy bessette]

Thanks Mark.

[Brian Holcombe]

Beautiful work, Andy!

[Mark Hennebury]

Nice work Andy.

[andy bessette]

Thanks fellas. Who says an old dog can't learn new tricks?

[Mark Bolton]

There seems to be an interesting sub-thread running through this thread _for me_ which may or may not be unique. I have been working with wood and construction for 30 years. I have an obsession with precision machining (you tube) though I will surely never be at that level, and also have a propensity to watch extensive youtube videos on sailing. Perhaps the problem is youtube, but I tend more to look to woodworking, machining, and sailing, as a common theme. Many of the sailing/cruising videos seem to be people with similar engineering/mechanical backgrounds. Perhaps its coincidence, perhaps its some goofy fascination with the mechanics of wind and fluid dynamics, perhaps its a notion for people of this mindset to want to get away.

Or perhaps its just a need for people who want to do something they are unwilling to pay market price for to figure out how to do it themselves. lol

[Brian Holcombe]

I've had jobs where one just shows up and does the work, mindlessly, and I can't suffer that. I need the wheels turning at times during the day to maintain my interest, exportation of various related subjects helps considerably.

I use for metal work also, so it's not just mental. Here are some nickel silver hinges with brass hinge pins. The pins are replaceable and precision and they're also custom made and exact.

It was entertaining for me to make this as accurately as I could possibly do on the bridgeport.

https://brianholcombewoodworker.com/wp-content/uploads/2019/06/fullsizeoutput_ec1.jpeg

https://brianholcombewoodworker.com/wp-content/uploads/2019/06/fullsizeoutput_eba.jpeg

[Brian Holcombe]

I added these jaws to the vise for this particular job, they have pins which allow one to clamp small parts are precise typical angles such as 15,30,45. They are also able to used as stops and parallels and they're accurately parallel to the jaws.

https://brianholcombewoodworker.com/wp-content/uploads/2019/08/fYdHTLyfRZu2YXl39RfAyQ.jpg

[Mark Bolton]

And then comes the question with regards to if that were a paying job, and you didnt just make the hinges because your payment was the reward of making them, what would the material and shop labor cost be for a pair of hinges like that? My guess would be a full days work (if your fast) including drawing/sketching, plus materials. $300-400 a pair?

[Bill Dufour]

Brian what are those vice jaws called? they are not 123 blocks and they are not a sine plate. I need to make a accurate 30 degree taper for a saw arbor and I am having a time getting it correct. I have swung the compound to 15 degrees and it is close but needs more test cuts. I think I need to mount a test indicator and look for zero deflection on the existing one I am trying to copy.
Bill D.

[Art Mann]

I hope no absolute beginner gets the false impression that this sort of measurement accuracy and instrumentation is necessary for doing first class woodworking.

[Brian Holcombe]

Brian what are those vice jaws called? they are not 123 blocks and they are not a sine plate. I need to make a accurate 30 degree taper for a saw arbor and I am having a time getting it correct. I have swung the compound to 15 degrees and it is close but needs more test cuts. I think I need to mount a test indicator and look for zero deflection on the existing one I am trying to copy.
Bill D.

Bill, they are Kurt 3 in one vise jaws, they could certainly work for you if you have a Kurt vise.

[andy bessette]

In case there is any interest in old machinery, here's a photo of my old Index mill and the rotary table I used to create the boom end fitting.

https://i.postimg.cc/5004PwmS/shop-4.jpg (https://postimages.org/)

[David Buchhauser]

Nice!! I've seen this photo before on another thread about planers.
David

[Brian Holcombe]

Nice setup, Andy!

Isn't it amazing how many tool chests one winds up with after a while?

[Andrew Gibson]

I hope no absolute beginner gets the false impression that this sort of measurement accuracy and instrumentation is necessary for doing first class woodworking.

Good point Art. While I do love some fine measuring tools and dabble in the automotive world building engines, body work, and welding, I have not had the chance to do much machine work, though my day job does have me working on the design and fabrication side and communicating heavily with machine shops. There definitely is plenty that can be gained from this sort of work in woodworking.

I do however believe it is very easy to get caught up in the precision of it all and many woodworkers I speak to get obsessed with measurements, settings, and details they loose track of the right brain side of woodworking. "I cant use this that or the other because its out by .001". My favorite person to talk about when things start getting to heavily into the "machinist side of things is Andre Charles Boulle. A French guy from around 1700 that created some of the most amazing woodwork ever created, combining brass, tortoise shell, and ebony... and I doubt he owned a caliper.

[Brian Holcombe]

Part of learning a craft is learning when to do so and when not to do so. Learning when to do by hand and when by machine, learning when to take fine measurements and when not to.

This is something that must develop over time, but in my opinion having a wider range of information available is not a bad thing. There are plenty of times when I read back through advanced level info and have a 'got-it' moment that didn't occur to me at the time. Should I have been kept from that information because I did not understand its purpose years ago?

More to the point, should we stop discussing industrial machine tools because someone may interpret them as necessary? Should we also stop discussion fine hand tools because they may also be deemed necessary?

Perhaps we can produce information and simply let people interpret it as they will and consume it as they may using it to their benefit when it becomes beneficial to them.

[Joe Calhoon]

Brian,
thank you for posting this. This is very thought provoking and has caused me to review my metrology methods and how they apply to my woodworking. No time to post right now but add my thoughts about this when I have some time.

[Edwin Santos]

I do however believe it is very easy to get caught up in the precision of it all and many woodworkers I speak to get obsessed with measurements, settings, and details they loose track of the right brain side of woodworking. "I cant use this that or the other because its out by .001". My favorite person to talk about when things start getting to heavily into the "machinist side of things is Andre Charles Boulle. A French guy from around 1700 that created some of the most amazing woodwork ever created, combining brass, tortoise shell, and ebony... and I doubt he owned a caliper.



I think this is a valid point. Like all things, this subject is personal, which is to say if one is wired with a machinist's or engineer's mentality, I can see where it would be rewarding and maybe even comforting to pursue super high levels of precision.

I think it's important to note, that working this way is a matter of personal preference, not necessity.

After all, traditional methods of woodworking have not required the types of super high precision being discussed here. I like to remind myself that the average human hair is about .004. So working to thousandths is basically working to a fourth of a hair. Plus wood is an organic ever moving material. Plus we don't work in clean rooms, so there's that little bit of sawdust that enters the picture.

But if a person enjoys the machinist approach to the craft of woodworking, I say by all means have at it.
For me, I'm willing to go partway down the metrology road, but too far gets me into the law of diminishing returns maybe because I'm not working in volume and partly because of my own inclination. It's very interesting though and thanks for sharing.

[Brian Holcombe]

Glad that we’re continuing an interesting discussion and glad you guys are getting something out of this. I felt I should do a deeper dive because the basics are already out there. I wanted to scratch below the surface.

A note on Boulle and cabinetmakers of that era, ‘a French guy’ does not describe that operation. He was running one of the most famous shops working on royal commissions, not a one man shop. They had staff that were highly specialized, so apprentices for basic joinery work, joiners for prep and advanced joinery work, highly skilled workers for veneer, shell and brass individually. All that comes together in a way that is near impossible to reproduce. I’m sure they actually did own vernier calipers, which were invented in 1631 in France and would be very relevant to veneer making.

[Andrew Gibson]

Part of learning a craft is learning when to do so and when not to do so. Learning when to do by hand and when by machine, learning when to take fine measurements and when not to.

This is something that must develop over time, but in my opinion having a wider range of information available is not a bad thing. There are plenty of times when I read back through advanced level info and have a 'got-it' moment that didn't occur to me at the time. Should I have been kept from that information because I did not understand its purpose years ago?

More to the point, should we stop discussing industrial machine tools because someone may interpret them as necessary? Should we also stop discussion fine hand tools because they may also be deemed necessary?

Perhaps we can produce information and simply let people interpret it as they will and consume it as they may using it to their benefit when it becomes beneficial to them.

How does the old saying go? Knowledge is knowing what tool to use, wisdom is knowing when to use it.
Years ago when I started down the path of building instruments my biggest fear was, can I build to the necessary level of precision. Highly accurate measurements are absolutely necessary. Execution is absolutely necessary and for me required a mix of machinery and had tool skills. Knowledge of the material and the way it behaves is absolutely necessary. If you are missing any of the three the end result will suffer.
Instrument work for me is very enjoyable because it pushes me in opposite directions of artistic and technical at the same time.
With everything we make the concept of tolerance is key.

Brian, this is a great thread and a very enjoyable and thought provoking for me.

[Andrew Gibson]

Glad that we’re continuing an interesting discussion and glad you guys are getting something out of this. I felt I should do a deeper dive because the basics are already out there. I wanted to scratch below the surface.

A note on Boulle and cabinetmakers of that era, ‘a French guy’ does not describe that operation. He was running one of the most famous shops working on royal commissions, not a one man shop. They had staff that were highly specialized, so apprentices for basic joinery work, joiners for prep and advanced joinery work, highly skilled workers for veneer, shell and brass individually. All that comes together in a way that is near impossible to reproduce. I’m sure they actually did own vernier calipers, which were invented in 1631 in France and would be very relevant to veneer making.

I meant this as a bit of hyperbole. I have always seen the work of Boulle as an inspiration simply to do better work and stop making excuses.

[Mark Hennebury]

Those that come from the metalwork and engineering world have mindset and tool set that they bring with them into woodworking.

Metalwork and engineering is about measurement. It is all about numbers. Numbers are specified, parts are measured and verified.
Woodworking is about fit, not measurement*

*Woodworking is a different world, at least the kind of woodworking that I do.
For reference; I made furniture, tables chairs, cabinets etc. I did lots of nice joinery work. I worked a combination of hand tools and stationary power tools,some automatic, like mortise and tenon machinery.

Woodworking / furniture making, has no specifications demanded by customers. No customer ever asked for + or -0.001" tolerance on a mortise and tenon joint, or even demanded a mortise and tenon joint in the first place. No customer ever pulled out there micrometer to check the table leg size.

While metalwork is governed by specifications and function, Woodworking is a fashion industry governed by the whim de jour. What tolerance you work to is it is pretty much all up to you. Your customer wont request or check your joinery work.

Although "high precision" is not necessarily a requirement in woodworking, it can be a big help in getting complex assemblies completed without any problems and can make for a very high quality product and of course give the maker a lot of personal satisfaction.

For those that want to do high end work with the finest joinery work and the tightest tolerance, it can pretty much be achieved without measuring anything.
There are many ways to do things and it helps if you have a broad scope to choose which way and when.
I have a lot of measuring tools, micrometers, camel back straight edges and granite surface plates etc.
But i did't always, i learned to do without all of the fancy measuring equipment.

Woodworking is about relationships; and when you learn to understand them and apply them, you can achieve as high a degree of precision as anyone, anywhere.
Doing high end work is not just about the tools. It is a mindset, its about thinking and visualizing in three dimensions, its about understanding the relation ships between parts and referencing, its about developing a system, and project management. It is about personal training, patience and discipline to follow every step of the process. every time.

As an example; when i make mortise and tenon joints with, lets say, my slot mortiser i choose the mortise bit, lets say 1/2" bit. I will cut the mortise in a scrap piece. then set up the tenoner and cut a scrap test piece to test the thickness fit only, when i have the thickness a smooth fit, i then set the tenon width to be a tight fit on the ends or the mortise. The reason i do the mortise first is simple; it size is governed buy the bit diameter. When i cut the tenon, i check one dimension at a time, so i can feel the fit of each, I don't want the tenon too tight in thickness as it can split the grain, but i want it tight on the end where it wont split. What the actual sizes are i don't know or care, but i bet they are as close or closer than any would get with working from calipers. The quality of your joints is a lot dependent on the quality of you machinery, its ability to do accurate and repeatable work, and also the tooling being the correct geometry and properly sharpened.

Measuring and measuring tools are an important part to learn to understand and use (but just like starting off with hand tools, i now understand the machinery that i use a lot better) i believe that you should first learn without measuring equipment.
I have seen many examples of people with high end measuring tools struggling to set up a machine because they cant "see" the relationship of the parts and geometry of the planes and axis. Developing the mindset is critical.

Once you learn without measuring tools your mind thinks in relative terms. Then add the knowledge of measuring tools and you will understand how and when to apply them.
Metrology is fascinating and another part of the education of a woodworker and we are lucky to have Brian contribute his knowledge to the collective.
Thoroughly enjoying the discussion.





Good point Art. While I do love some fine measuring tools and dabble in the automotive world building engines, body work, and welding, I have not had the chance to do much machine work, though my day job does have me working on the design and fabrication side and communicating heavily with machine shops. There definitely is plenty that can be gained from this sort of work in woodworking.

I do however believe it is very easy to get caught up in the precision of it all and many woodworkers I speak to get obsessed with measurements, settings, and details they loose track of the right brain side of woodworking. "I cant use this that or the other because its out by .001". My favorite person to talk about when things start getting to heavily into the "machinist side of things is Andre Charles Boulle. A French guy from around 1700 that created some of the most amazing woodwork ever created, combining brass, tortoise shell, and ebony... and I doubt he owned a caliper.

[andy bessette]

Nice setup, Andy!

Isn't it amazing how many tool chests one winds up with after a while?

Thank you. Especially in precision machining the amount of tooling and instrumentation required seems never ending.

Regarding the varied need for precise metrology in woodworking, it greatly depends on the type of woodworking. Some, like carving for example, may be done entirely by eye. Other types might require a high degree of interchangeability in very complex assemblies. I regularly use dial calipers in my woodwork, but I also get a lot of use from a tiny 10' tape that is always with me.

[Jared Sankovich]

Count me in the precision measurement camp. Im trying to hit .001" on certain things.

Though I tend to leave my micrometers and surface plate in my machine shop.
http://img.photobucket.com/albums/v695/jar944/IMG_20181201_131022_595_zpseudrdtqe.jpg (http://smg.photobucket.com/user/jar944/media/IMG_20181201_131022_595_zpseudrdtqe.jpg.html)

http://img.photobucket.com/albums/v695/jar944/IMG_20181130_163802_036_zpsgnycdgty.jpg (http://smg.photobucket.com/user/jar944/media/IMG_20181130_163802_036_zpsgnycdgty.jpg.html)

[Darcy Warner]

Thank goodness I mostly just match old stuff, cant make that look too good or its obvious it's been replaced

[James Pallas]

Very interesting discussion. I’m definitely a believer in good layout tools no mater the discipline. The issue I have always had with machine tools and woodworking tools in the same area is contamination. Dust and machine tools don’t play well. Likewise for metal contamination on wood. Machine tools can do some wonderful things for woodworkers. CNC May be the answer. Machine tool made for woodworking good, lots of sawdust floating into your metal lathe not so good. It would be the same for having your blacksmith shop in your machine room. The layout tools are important for all disciplines. Just some thoughts on my part.

[David Buchhauser]

I think this is a valid point. Like all things, this subject is personal, which is to say if one is wired with a machinist's or engineer's mentality, I can see where it would be rewarding and maybe even comforting to pursue super high levels of precision.

I think it's important to note, that working this way is a matter of personal preference, not necessity.

After all, traditional methods of woodworking have not required the types of super high precision being discussed here. I like to remind myself that the average human hair is about .004. So working to thousandths is basically working to a fourth of a hair. Plus wood is an organic ever moving material. Plus we don't work in clean rooms, so there's that little bit of sawdust that enters the picture.

But if a person enjoys the machinist approach to the craft of woodworking, I say by all means have at it.
For me, I'm willing to go partway down the metrology road, but too far gets me into the law of diminishing returns maybe because I'm not working in volume and partly because of my own inclination. It's very interesting though and thanks for sharing.

I appreciate you thoughts Edwin. I do both wood and metal, but I mostly leave my Mitutoyo Height Master, CMM, Optical Comparator, Starrett surface plate, Brown & Sharp sine bar, sine vises, Starrett planer gauges, precision gauge blocks and pins, and many of my other precision tools that would normally be used for precision metal working/machining dedicated to just that. With the exception of the dial caliper and maybe some gauge blocks - I just don't see the need for any of these other precision measuring instruments with respect to the wood working genre.

I did enjoy seeing the photos of the accumulation of Mitutoyo tools that the OP has acquired, and appreciate his investment into his tools and career.

After perusing his website, I now have a newfound appreciation for the current market value for his type of services. I suppose that I am fortunate that I can do most of this myself.

And I whole heartily wish him well with the persuit of his woodworking endeavours.



David

[David Buchhauser]

I hope no absolute beginner gets the false impression that this sort of measurement accuracy and instrumentation is necessary for doing first class woodworking.

Hi Art,
I agree with you 100%. Most of us here on SMC (seasoned members- myself not included) are far from "beginners". It would be a shame for some new comers reading this to reach the conclusion that they need all these "fancy measuring tools" to succeed with their newfound hobby. I agree - Let's Keep It Simple!
David

[Art Mann]

More to the point, should we stop discussing industrial machine tools because someone may interpret them as necessary? Should we also stop discussion fine hand tools because they may also be deemed necessary?



We should stop discussing machine tools as if they were necessary for making fine furniture and cabinetry. You did not make that point clear. There is a place for discussing fine hand tools on this forum. It is called "Neanderthal Heaven". That is where people go to discuss such things. There is also a place for discussing machine tools and instruments. It is called "Metalworking". What is wrong with discussing it there?

As far as I know, nobody before me stated that you can do first class woodworking without machine tool accuracy. That omission could lead some readers to a false conclusion. What is wrong with making the point clear? Do you really disagree with it?

[Brian Holcombe]

Hi Art,
I agree with you 100%. Most of us here on SMC (seasoned members- myself not included) are far from "beginners". It would be a shame for some new comers reading this to reach the conclusion that they need all these "fancy measuring tools" to succeed with their newfound hobby. I agree - Let's Keep It Simple!
David

Did you read the article? Point is mainly that I’m using these tools for setup of machine tools. Not everything you run into is simple and having an understanding beyond the basics is often required.

If one had a tilt spindle shaper then wanted to put a tenoning head on it, wouldn’t you tram it to the table first rather than take the chance that you’re going to cut tenons at a slight angle.

If you decided not to, then run a few hundred tenons, what then? Throw them out, cut them undersize, build out of alignment? Is that something you’ll notice right away or when every single joint gaps in your run? Are you going to immediately realize why or does it take a few hours?

What if you need to realign your mortiser, something used for cutting hundreds of mortises in expensive material that makes the job unprofitable if you need to replace it all. Should you get your good tools or is this a better job for the eyeball gauge?

Is everything always immediately apparent in test cuts?

[David Buchhauser]

We should stop discussing machine tools as if they were necessary for making fine furniture and cabinetry. You did not make that point clear. There is a place for discussing fine hand tools on this forum. It is called "Neanderthal Heaven". That is where people go to discuss such things. There is also a place for discussing machine tools and instruments. It is called "Metalworking". What is wrong with discussing it there?

As far as I know, nobody before me stated that you can do first class woodworking without machine tool accuracy. That omission could lead some readers to a false conclusion. What is wrong with making the point clear? Do you really disagree with it?

Hi Art,
I feel that you are 100% correct. We have forum topics for hand tools as well as machine tools. This may have not been an appropriate venue for the OP's topic. He did manage to start a topic of interest to many, including some or the moderators. Maybe they should consider moving this to a more appropriate place. In any case, this did afford me the opportunity to peruse his website.
David

[David Buchhauser]

Did you read the article? Point is mainly that I’m using these tools for setup of machine tools. Not everything you run into is simple and having an understanding beyond the basics is often required.

If one had a tilt spindle shaper then wanted to put a tenoning head on it, wouldn’t you tram it to the table first rather than take the chance that you’re going to cut tenons at a slight angle.

If you decided not to, then run a few hundred tenons, what then? Throw them out, cut them undersize, build out of alignment? Is that something you’ll notice right away or when every single joint gaps in your run? Are you going to immediately realize why or does it take a few hours?

What if you need to realign your mortiser, something used for cutting hundreds of mortises in expensive material that makes the job unprofitable if you need to replace it all. Should you get your good tools or is this a better job for the eyeball gauge?

Is everything always immediately apparent in test cuts?

Yes - I did read your article. I do understand that your apparent level of expertise far exceeds that of most of the members here - particularly with regard to your previous work as a machinist and metal worker. Never the less, I take Art's point very well. This is all great stuff for the highly advanced woodworker, but is most probably not applicable to the average enthusiast.
David

[Brian Holcombe]

We should stop discussing machine tools as if they were necessary for making fine furniture and cabinetry. You did not make that point clear. There is a place for discussing fine hand tools on this forum. It is called "Neanderthal Heaven". That is where people go to discuss such things. There is also a place for discussing machine tools and instruments. It is called "Metalworking". What is wrong with discussing it there?

As far as I know, nobody before me stated that you can do first class woodworking without machine tool accuracy. That omission could lead some readers to a false conclusion. What is wrong with making the point clear? Do you really disagree with it?

The point of my article is that when you actually do want accurate machine tools, you need to check them. It does not say anything about it being required for fine woodworking. In fact if you search my site you’ll see where I build projects using nothing but a basic set of hand tools.

Ive added machines over the past few years and initially took the approach of ‘check the work’ problem is that you're Using a small work piece to check a long measurement. Better the other way around, which is why one usually trams a large circle.

[Kevin Jenness]

I don't think this forum is the wrong place for this thread, as "power tools" do need accurate setup which involves more or less precise measuring tools.

My first reaction was " This is a bit precious- measuring the measuring tools" but I must admit to a similar general approach to Brian's in the shop in a quest for accuracy and efficiency. I don't work much with metal so no sine bars or micrometers but I use a digital caliper and engineer's square every day and make frequent use of dial indicators, taper gauges and straightedges to check and adjust the machinery I work with. It's interesting to see the spillover from machine shop experience to the woodshop, and it is as valid in its place as the more free approach I bring to, say, turning.

Here are a several tools I use frequently. The large taper gauge is quite useful for gauging reveals when hanging doors and the smaller one is in regular use for establishing Z-zero on the cnc router. The flat magnetic-back dial indicator is handy for fine adjustment of fences.413633413634

[Mark Hennebury]

I also don't have a problem with the thread or its place.

Any opportunity to learn anything is worthwhile.

It seems that if anyone shows anything more than beginners methods, there is some kind of backlash to protect them from being discouraged from seeing something that they cant do. The fact is beginners cant do anything, they are beginners, this is how the learn by seeing amazing stuff and being motivated to want to learn to do it.

Many different ideas on woodworking and levels, i have no problem seeing all of them showcased; take what you want or what you can, and move on.

[Brian Holcombe]

I’d like to bring up one of the more aggravating things I’ve had to solve. I have a slot mortiser, the settings it arrived with were good enough only to pass a very rudimentary inspection. Cut a small mortise with it, it’s passable, cut a long mortise with it and it started showing odd things.

I started digging into it a bit and begin to realize that I need to get it right before I do anymore checking of the output.

First I determine that the spindle must be parallel to the machine ways, one typically assumes that the factory does this and their was a stack of shims at the back of the motor.

Easy fix, travel and indicate the spindle on top and side. Why? Because the table can be eliminated from the measurement. It was originally shimmed to match the table by whom ever set it up previously and they were both out of parallel to the machine ways. The result was a mortise with a taper on one wall so the top of the mortise was a different size than the bottom.

Next the table is made parallel to the ways. Indicate down the table at a few points and along the front edge, but only after determining that the table is reasonably flat. This is made more difficult by the four screws that hold the table in place and the fact that they can influence flatness.

The hard way to do this is test cutting, which is an hours long process which will provide mediocre results that are affected by things like bit deflection.

[Lee Schierer]

Moving toward higher accuracy, the digital protractor which reads out to a tenth of a degree. This protractor is useful for machine setup in less demanding situations.
413899

In higher precision machine setup and for checking angularity, it is often done one of two ways, angle blocks or a sine bar. Angle blocks are precisely ground small blocks which can be stacked together to form a very accurate representation of a given angle. A sine bar is a precision bar with two round portions. The sine bar provides a fixed distance for the hypotenuse allowing the user to calculate any angle and bring the bar to that angle by using gauge blocks.


Distance

Distance measurements are done with varying degree of accuracy depending on their need. Different tools for different tasks, we separate shop standards and high precision measuring from basic layout devices which are referenced to those shop standards for quality then used for lower precision tasks.

The most basic tool is the scale, or rule, depending on your preference. The scale can be relied upon for measuring in scenarios where the accuracy needed is less than the width of the tick marks and they’re often available up to about 60″ in length in steel.

Used in conjunction with a scale, the combination square can used for measuring from an edge.
413900

When measuring from a 45 degree position one can use this feature of the combination square.
413901

When measuring from an angle outside of 90 or 45 the protractor head is used.
413902

When measuring from a square corner toward center, or finding center of square corner one may chose to use another part of the combination square kit, the center head.
413903

Next is the double square, featuring a shorter blade for getting into tighter spaces. The double square is a wonderful device for small scale layout and useful in many scenarios where high precision is unnecessary.
413904

Followed by a higher precision, but smaller double square made by Starrett and featuring a series of blades which allow it to be used in tight spaces.
413905

Another way to measure from an edge is a kegaki scribing gauge, this one manufactured by Matsui Measure. This provides a similar degree of precision as the combination square, but it has a longer reference face which is handy to scribe against.
413906

[Lee Schierer]

Following is a piece that has a role in both the carpenter’s kit along with those of the cabinet shop, this is the square rule. In this case it is a Sashigane, or Japanese carpentry square.
413907

Processing toward a greater degree of accuracy we first move into the vernier caliper, with digital readout in this case. This particular model is provided with its own standard, which is intended to be measured at 20 degrees celcius.
413908

From there we move into the indicator, also digital in this case. Indicators are available which measure very finely. This particular one measures to five tenths (.0005″). Indicators are a multi function tool, depending on how they’re fixtured, they’re a great device for taking measurements directly from a machine or for use in a comparator.
413909

The indicator can also be used in a magnetic base and mounted directly on iron or steel surfaces.
413910

A finer reading indicator known as the test indicator is often used for more detailed work, it has a much smaller range of motion and it can provide a higher degree of accuracy. These commonly read to a tenth of a thousandth of an inch. When combined with fixturing devices such as the Magnetic stand, spindle mount or comparator it is very useful for a variety of indicating needs. I typically use a test indicator for tramming work.
413911

For height, the height gage is used, digital in this case. This can be used for precise comparison in addition to gauging of height. This is a wonderful device for checking tooling heights but must be used with extreme care as the tip is carbide.
413912

More accurate still we move into the micrometer. This digital mic can read down to microns in metric or hundred thousandths in imperial, I don’t use a lot of micrometers in my work, so I have a 1″ model only.
413913

Depth is best measured by a depth micrometer, this one included a set of six probes and allow it to measure from between 0-6″ of depth.
413914

[Lee Schierer]

Johansson Blocks or ‘Jo’ blocks are a gauge block system for producing accurate lengths. These are lapped to size and calibrated by Mitutoyo, the deviation from standard is provided in a sheet and measured in millionths of an inch, they’re effectively perfect to my ability to measure.
413917

1,2,3 and 4,5,6 blocks are similar to Jo blocks but they’re not quite as accurate in most cases. These blocks are ground square and to size. These are a fairly inexpensive set of blocks that I use for setup on the milling machine (mainly). They’re also handy for other forms of setup and reference. The block is being used as a stop in this situation.
413918


Standardization

With our inspection tools in place we can begin the process of checking them to ensure that they are reading accurately. ASME outlines exactly how to calibrate inspection equipment, however for the purpose of this post I will detail my own more basic process. The goal of this exercise is to ensure that all of the tools are reading within a reasonable degree of one another. That degree varies depending on the tool class and its manufacturer spec along with the requirements of the workshop.

Initial testing will be conducted with the use of gauge blocks. I make assumption that the gauge blocks are accurate and one can reinforce the quality of that assumption by measuring multiple blocks with each instrument. These blocks are certified and come from a manufacture held to international quality standards for accuracy, they’re graded for accuracy and provided with a certification.

These blocks are made to be accurate to size at 20 degrees Celsius (68 degrees Fahrenheit), so the first thing to be aware of is the temperature being measured it. Steel expands at a coefficient of 0.00000645 per inch degree F, so a 4″ block could increase in size by .0005″ if it were measured at 90 degrees rather than 68 degrees. Doesn’t sound like much, but that always depends on what your after and it should be calculated for when measuring outside of 68 degrees.

In order to eliminate possible variables I decided to check a few things before getting started with comparison testing. My first step was to apply compound to my granite plate and check my indicator bases for contact. My indicator bases are flat so I won’t need to worry about them rocking and causing a false read during any of the tests. I’ve verified all squares against each other and against the angle plate, they all agree with one another, save for the combination squares which deviate by a couple thousandths except the mini Starrett.

Using the standards I begin by checking my calipers. It’s important to have the feel for measuring down pat, but having a number of years on micrometers and calipers I have a consistent feel. The calipers much be clean where they will touch measuring devices and the standards must also be clean. I oil things between uses and so I wipe the oil off before starting. This should be done with multiple standards to see if the error remains constant or if it increases.

The main jaws I measure in three places using the thin side of the measuring block to ensure that the jaws are parallel to one another. These are spot on, so far, measuring exactly as they should.
413919 413920 413921

Next I measure the standard using the back of the main jaw, this provides a deviation of .0015″. More than I prefer, but it’s within a reasonable standard, especially for a part of the tool I don’t much use.
413922

Next I measure the prob, while the measurement doesn’t show in this photo, it is 2.000″
413923

[Lee Schierer]

Next I check the depth micrometer and the outside micrometer to ensure that they’re reading accurately. The first step I take is to ensure an accurate zero position. This is one in which the dial stops at exactly 0.00000″ when the spindle closes against the anvil on the micrometer and when the spindle is flush against the surface plate on the depth micrometer. The digital aspect of the gauge can be easy reset to zero if it reads otherwise. I use the micrometer’s ratchet’s to ensure that the positions are closed down to accurately.

After which I want to establish that the micrometer is reading distances accurately, so I use two blocks, one in the middle of the range and one at the extreme of the range to ensure that these measurements are accurate.

It’s important that the tools be in good order as well, in this case the depth mic shows staining on the side of the spindle, this is due to how it was stored before I received it. The spindle is in the process of being replaced and the new spindle will be calibrated again once it arrives. Its important that precision instruments be kept in good condition, their tolerances can be deteriorated by rust.
413924 413925 413926

413927 413928 413929

[Lee Schierer]

The same procedure is applied to the height gauge, first setting it to zero using the surface plate.
413930 413931 413932

The digital indicator is affixed to a comparator stand. The probe is mounted so that it contacts the top of the anvil, then the indicator is set to zero. The probe is lifted, checking blocks are slid into place and the probe placed on the blocks. This measures the amount of travel. A comparator stand maintains a square position for the indicator so the travel is accurate.
413933 413934

In the next post of this series I will begin detailing my process for standardizing machine fence read outs and specifying a few cases where transferring measurements is an improvement in accuracy and expedience. Thank you for reading this post and I look forward to your comments.

[Brian Holcombe]

Thank you, Lee!

[Patrick McCarthy]

I don’t understand the criticism of this thread. Some are happy to mark with chalk and cut with an axe, which is fine in some situations. Seeking to better understand ALL of the factors that influence the final outcome does not diminish craftsmanship, nor does it dishonor the wood. Using machinist tools to set up our tools seems very sensible. Indeed, it seems to be the best way to make sure the only variable is the wood.

A deeper understanding of the process is simply additional knowledge; additional knowledge/understanding is inherently a good thing.

Less knowledge and less understanding of any subject would seem to present more danger. One need not always use the entirety of the font of knowledge they are able to acquire, but that reservoir of information/understanding can only add to the overall appreciation of the risks/dynamics, and thereby help avoid problems or solve them when they appear.

I didn’t perceive that Brian was advocating that one must do anything “his” way. He was prompting a thoughtful discussion.

Even those that just read comic books (or “graphic novels”?) wouldn’t suffer by being exposed to prevailing thoughts on literary analysis as to the structure of a novel, or why Melville’s Moby Dick is considered important, nor what Cervantes was addressing in Man of La Mancha/ Don Quixote, or why that English fellow who wrote all those plays is still quoted (and, often as not, misquoted . . . . “The lady doth protest too much, me thinks” rather than vice versa) frequently today. Breath of knowledge can only be of benefit. Being familiar with William Shakespeare does not mean that we must speak like him.

No wonder this forum is dying a slow death.

Brian, i believe - despite my pessimism - many here still have open minds and are appreciative of the information and content you provide.

[Lee Schierer]

Thank you, Lee!

No problem, if you do future posts, remember that photos are limited to 8 per post so immediately make multiple replies to your own post so that you will have consecutive space to cover your entire post with many photos.

[Flamone LaChaud]

Some of the discussions remind me of this particular piece of sage observation, rendered in a timeless artistic fashion.
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[Prashun Patel]

This is the appropriate venue for the OP's topic. Set up and measurement applies to all 'types' of woodworking. Given that his article is a reflection on his desire for efficiency for production, repeatable work, one might argue that it's MORE appropriate here than in Neander. The OP usually posts there, so I am sure his decision to post here was not cavalier.

I think we don't give the 'beginner' enough credit. They can appreciate a variety of threads for what they are.

[Brian Holcombe]

Thanks, Patrick. I’ve gotten a lot of positive respondents here and via email. I am glad that many people find it useful or thought provoking.

[Dan Friedrichs]

When is part 2 coming? :D

[andrew whicker]

One's "art" is whatever one wants it to be. Some artists throw paint on a canvas with a brush (Pollock) and others will be technical masters (Degas).

I love Brian's work. If I had the means, I'd hire him to build me something : )

To each his/her own.

[Brian Holcombe]

Thanks, Andrew!

Dan, maybe never. :D Probably in a few weeks.

[Patrick Walsh]

I have not been around much “working” like freakin crazy again.

But it seems to me you might and I say might be keeping the nightly skilled talented portion of this website kicking at the moment.

I agree all perfective are of value and interest. Depending on where one starts and ends and is in the process clearly ones interest will be peaked by beginner topics, intermediate or advanced.

What I think is important here is that if you don’t know the question to ask you can’t seek the answer. And this website from my infancy in cabinet making offered me many perspective of many people at various stages of the learning or execution curve. I found that extremely valuable.

I personally even when in the infancy stages find the advanced topics and or subject matter most useful as if you read between the lines there is so much to learn.

It takes so much of ones time to share even on a forum based platform. Without those willing to take that time and the desire to share we are all left where we were 20-30 years ago to learn. A library, paying for instruction of some sort or if you like me teaching yourself.

Anyway, thanks Brian and hope life is well.

[Joe Calhoon]

Glad this thread is back! I’ve enjoyed it and absolutely think it belongs here. Some recent machine restorations have peaked my interest in metalworking.


My business is millwork and joinery and the thread has me thinking about how my measuring process has evolved over 40 years. No doubt it’s possible to do first class work with minimal measuring methods. In my early days precision measuring was done by pulling a inch on the tape. Advanced and more precise measuring can make machine repeatability- setup quicker and more accurate. The days of producing large quantities of woodwork are gone, now it’s more about small batch sizes and one off work in the custom sector. And also for the home shop that wants to work more efficiently.


No machinist skills here but I have some thoughts on how woodworking machines can be adjusted and maintained for accuracy with a few tools. For machine setup it think the essentials are a couple good squares, ( the Lamb square is my favorite) a good straight edge, feeler gauges, digital height gauge, dial indicator, digital calipers and a protractor. The protractor and cheap dial indicator are marginal and on the list to upgrade. The long measuring stick in the photo is for site measuring and should not be in the picture for machine setup.

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For checking wood parts for accuracy the digital calipers, small Starrett square, tape, folding rule and 10 mm square bar are my go to. Last picture shows how the square bar is used.
I work in millimeters and find 0.1 or 0.2mm is close enough for most joinery. That’s about .004-.007 inch.


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[Kevin Jenness]

You can quibble about the proper forum for this topic but Patrick is right to point out the value of sharing information, especially when it comes from a craftsman with technical expertise who can write clearly. I can't link to it, but there is currently an intriguing thread about handrailing and stairbuilding on the architectural woodworking forum at woodweb with reference to what might be the market value of a book on the field by a working professional who can't take the time from making a living to document how he does it. How much would you pay for a new classic on stairbuilding, or whatever branch of woodworking you are devoted to- and how much are you willing to pay to keep this site going?

[Brian Holcombe]

Thanks, gents. Appreciate the comments. It is time consuming, it took me a month’s worth of early morning writing and documentation to create the post because I can usually only spare about 15min at a time.

[Brian Holcombe]

Glad this thread is back! I’ve enjoyed it and absolutely think it belongs here. Some recent machine restorations have peaked my interest in metalworking.


My business is millwork and joinery and the thread has me thinking about how my measuring process has evolved over 40 years. No doubt it’s possible to do first class work with minimal measuring methods. In my early days precision measuring was done by pulling a inch on the tape. Advanced and more precise measuring can make machine repeatability- setup quicker and more accurate. The days of producing large quantities of woodwork are gone, now it’s more about small batch sizes and one off work in the custom sector. And also for the home shop that wants to work more efficiently.


No machinist skills here but I have some thoughts on how woodworking machines can be adjusted and maintained for accuracy with a few tools. For machine setup it think the essentials are a couple good squares, ( the Lamb square is my favorite) a good straight edge, feeler gauges, digital height gauge, dial indicator, digital calipers and a protractor. The protractor and cheap dial indicator are marginal and on the list to upgrade. The long measuring stick in the photo is for site measuring and should not be in the picture for machine setup.

414020


For checking wood parts for accuracy the digital calipers, small Starrett square, tape, folding rule and 10 mm square bar are my go to. Last picture shows how the square bar is used.
I work in millimeters and find 0.1 or 0.2mm is close enough for most joinery. That’s about .004-.007 inch.


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414022



Joe, thanks for sharing your approach. I had a feeling you'd be using height gages as well, it was a game changer for me. I used to hang a double bevel off the tool and set the height that way. It was accurate but the height gauge is always spot on.

At the machine shop we used precision levels to setup machinery and also for setting up rough cuts. I'm not sure how useful it will be in the woodshop but I decided to add one for aiding in machine setup. A little easier than using a carpenters level or a cast iron level.

[mreza Salav]

Very interesting thread. I always strive to be as precise and as good as possible but I mostly work/build for myself. I hope those of you who woodwork/cabinet making to 0.001" get paid enough.
When I was building our house and various things for it a few builder in the area stopped by and asked if I was willing to build them similar things. My response was you can't afford me. I don't do this for a living and I am sure if I was doing it the way I work for myself I won't be paid enough.

[Donn Ward]

Very interesting, informative, and well-written; thank you!

[David Buchhauser]

Brian,
Lots of good information here. I have reread your column (more closely) and I do see the merit of your application with these instruments. I feel bad about some of my previous comments. Heat of the moment - if you know what I mean.
I will look forward to part 2. Glad you were able to get it back on the forum.
David

[Ole Anderson]

Thank you for the write-up Brian. Very well done sir!

I have a small granite surface plate, but it is only used as a base for sticky back abrasives in my scary sharp system. I recently acquired a few measuring instruments, but none of them are intended for use with a surface plate.

[Brian Holcombe]

Thanks, gents!

David, very much appreciate your comment, that means a lot to me.

Second post in this series should be coming up shortly.

[Donn Ward]

Very informative thread, I am enjoying it immensely. Thank you to those who are taking the time to put this information together for the rest of us, I am very appreciative.

[Pat Barry]

Brian, where is Page 2? The link in the original post is just refreshes the page as far as I can tell. Thanks

[Brian Holcombe]

Pat, it's on pages 4 and 5.

[Jeff Bartley]

Thanks for this Brian, I've thoroughly enjoyed the deep dive into metrology!

[Pat Barry]

This is where you really get to know people.


Pat, it's on pages 4 and 5.

Thanks. I see its under Lee's name. I was just skimming for yours.

Ps: maybe Lee can fix the link to redirect to the content on page 4?

[Brian Holcombe]

Thanks, Jeff!

Pat, happy to help. May be worth bringing this to his attention directly.