Marking gauge accuracy

[Kevin Hampshire]

I was reading an online review of a marking gauge and there were critiques about them being out of square. Am I missing something? Never worried about the fence on the gauge being square to the beam.

So does it have to be square for some reason?

[Jim Koepke]

As long as it is reasonably square it shouldn't be a major problem.

Imagine the cutting point being square to the beam and the fence off square. Then it could cause a problem if the cutting point is a wide blade or a wheel.

jtk

[glenn bradley]

Right, if I set the gauge via a rule for a specific measurement and the beam is at a 2* angle, my measurement is off. I would think that if the gauge were off enough to affect my joinery I would notice while using it. Certainly it should be perpendicular.

[Kevin Hampshire]

I agree that a cutting gauge with a blade should be square, but a marking gauge just has a pin. Kind of like using a fence on a router table versus table saw fence. Doesn't have to be square to the router bit but does have to be square to the saw blade.

Unless I'm missing something it seems like the fence to the beam could be pretty wonky out of kilter and still work perfectly as long as it locks up tight.

[david charlesworth]

When stem is out of square to face, the face can be thrown out of contact with a square edge.

Squareness is very important.

David Charlesworth

[glenn bradley]

When stem is out of square to face, the face can be thrown out of contact with a square edge.

Squareness is very important.

David Charlesworth

Yes, this. Think about it for a moment and you'll have an "ah-ha" moment.

[ian maybury]

Would it be correct to think that's due to a ploughing action by the blade/knife - wher the blade will want to run parallel to the reference edge, but this results in the stem/beam tiling the face?

[Derek Cohen]

Just try cutting a clean line with a cutting gauge where the knife is not aligned with the fence.

Regards from Perth

Derek

[Pat Barry]

Just try cutting a clean line with a cutting gauge where the knife is not aligned with the fence.

Regards from Perth

Derek
Knife gauge then the blade alignment is important to ensure proper tracking and marking. Pin marking gauge, then this is not an issue. Double pin gauge for morticing, etc, then squareness to the fence becomes important again. Now, if you have that knife gauge set to be slightly off square such that as you use it it has a tendency to pull the body up to your reference edge, and this still leaves a clean mark you are golden. It might take a relatively stiff marking blade for this to work (without blade bending deflection). With the grain marking is going to be somewhat troublesome on many types of wood regardless.

[Graham Haydon]

Pin gauges are less fussy, both mortice and marking. I can't imagine even bargain bin pin gauges have a head out of square enough to cause a real problem. Knife edges are a different matter. That's why I like pin gauges.

[Bill Davis1962]

Sqareness is important, the longer the fence, the more being square counts. Think of 3 points....the cutting knife and two extreme ends of the fence as a triangle. That triangle needs to be a right triangle to get the exact distance from the edge. I hope this helps.

[Graham Haydon]

The op asked about a marking gauge. I'm not sure if he mentioned a knife or a pin. If it's a knife in my book it's a cutting gauge and in that case the knife must be parallel to the headstock. If it's pin marking gauge it works on a circular pin, parallel to the headstock then does not matter. Perhaps the op could confirm the type of gauge?

[Mike Cogswell]

The op asked about a marking gauge. I'm not sure if he mentioned a knife or a pin. If it's a knife in my book it's a cutting gauge and in that case the knife must be parallel to the headstock. If it's pin marking gauge it works on a circular pin, parallel to the headstock then does not matter. Perhaps the op could confirm the type of gauge?

The type of gauge doesn't matter, it needs to be square to be accurate. David and Charles are absolutely correct. Think about it. As the fence angle relative to the arm changes away from square, the perpendicular distance of the marking point to the fence gets shorter while the distance from the point to the fence along the arm remains unchanged.

[david charlesworth]

Just to elaborate a little.

In use the stock face is pressed firmly against the face edge which should be square.

The stem has three possible positions.

1. Pointing up in the air so the pin is above the surface.
2. Pointing down so the face is displaced when the stem is pushed onto the surface. Thus causing error.
3. Laying correctly on the surface so that pin depth of cut can be controlled by pivoting on its leading edge.

I am certain that squareness matters. A decent gauge should be reasonably square but some cheap Sheffield ones are not. We cure them by adjusting the face by planing. If present, those redundant brass strips are simply reversed.

best wishes,
David

[Graham Haydon]

Hi Mike,

I might regret this but I'll try and knock up a video later. I do appreciate that there is a degree of accuracy required, I just can't recall ever checking a gauge for square.

Cheers

[Warren Mickley]

Hi Mike,

I might regret this but I'll try and knock up a video later. I do appreciate that there is a degree of accuracy required, I just can't recall ever checking a gauge for square.

Cheers

Last night I used a protractor to check a marking gauge I have used since 1962, the first time I checked. I found that the beam is 89 degrees to the head.

The sine of 89 degrees is .999847, so if I measure 5/8 perfectly parallel to the beam, instead of getting .62500 like I should, I get .62490, one ten thousandth of an inch off. The beam would have to be over 3 degrees off in order to register a .001 inch difference, and 10 degrees off to make a .01 inch difference.

A panel gauge is somewhat more vulnerable to angular discrepancy because of larger scale; a panel gauge at 89 degrees would yield 11.998 instead of 12.000. For a marking gauge I would say that the small discrepancy introduced by the gauge is dwarfed by discrepancies caused by my measuring and my ability to work to a line. And in many situations it is more important that several lines made by the gauge agree with each other than they agree with some theoretical number.

[Graham Haydon]

89 degrees! How dreadful :). "it is more important that several lines made by the gauge agree with each other" very much so.

[ian maybury]

I've not done a lot with gauges, but I'd imagine that while squareness of the beam to the head is a factor in the deal, that the issue that ultimately matters is to ensure that the the cutting edge of the knife is aligned so that the natural line it wants to cut along (in a grainless or homogeneous material - say MDF) is parallel to the fence/head.

Even this isn't necessarily what it might seem, in that if the bevels are put on in such a manner that the cutting edges are not aligned with the surface of the knife 'blade', then checking it for square relative to the beam or for being parallel to the head may be misleading.

While it wouldn't necessarily be ideal given the lack of a simple basis for alignment, there's theoretically the possibility that the beam could be significantly out of square to the head, and the knife blade out of square to the beam - and yet the knife could still cut parallel to the head as a result of the bevels being offset as a result of how it was ground/sharpened.

Then the wood grain comes into it. Depending on it's direction (especially if it's a fairly small angle removed from being in the the line you want the gauge to cut) it's going to create a tendency for the knife to want to track in a given direction. Which isn't going to be parallel to the reference edge. This will (with the drag that is always going to be present) try to cause the beam to swing around the head like a compass in one direction or another - which will tend to take the head out of parallel with/out of resting tight against the reference edge. The result may be that the line cut will be neither properly straight nor parallel to the reference edge.

This suggests that a big part of using a gauge is about ensuring that the head stays forced tight against the reference edge for the duration of the cut. The beam on a long gauge will meanwhile need to be stiff enough not to deflect by very much under the drag and forces which arise as a result of forcing the knife to cut in opposition to the grain along a line that's not it's natural one. (which is why applying some push as well as downward force at the knife end as well may not be a bad idea) For a given grain direction it's probably going to be easier to maintain this control while cutting in one direction rather than the other. There may be some benefit (especially on a long, more flexible and awkward to use gauge) in difficult cases in pushing the head tight against the reference edge and just pushing the knife down at intervals to prick guide marks. Which will verify if the subsequent cut line is one track - or which could even be used to line up a rule.

I guess a conical point has to be the only cutter that's not directional, but it of course has the disadvantage that it's frequently not going to cut very cleanly. If using a cutting tip there has to be benefit to keeping the blade fairly short or better still quite pointed - so that it's 'ploughing' or directional effect in the wood will be minimal...

[Brian Holcombe]

http://i27.photobucket.com/albums/c181/SpeedyGoomba/E3CA5284-B9C5-4FEB-8059-1DCE4A46843A_zpsyhpl3zty.jpg (http://s27.photobucket.com/user/SpeedyGoomba/media/E3CA5284-B9C5-4FEB-8059-1DCE4A46843A_zpsyhpl3zty.jpg.html)

http://i27.photobucket.com/albums/c181/SpeedyGoomba/DEA6A89C-C79D-4E7B-8EEA-6B037E620C0A_zpsicjd62i7.jpg (http://s27.photobucket.com/user/SpeedyGoomba/media/DEA6A89C-C79D-4E7B-8EEA-6B037E620C0A_zpsicjd62i7.jpg.html)

http://i27.photobucket.com/albums/c181/SpeedyGoomba/14168DAF-C7F2-4C36-A970-1E2F9A780A34_zpsywq8g65e.jpg (http://s27.photobucket.com/user/SpeedyGoomba/media/14168DAF-C7F2-4C36-A970-1E2F9A780A34_zpsywq8g65e.jpg.html)

http://i27.photobucket.com/albums/c181/SpeedyGoomba/6016A820-7C85-4F0F-B9BD-4907BAF24D92_zps5y3umvms.jpg (http://s27.photobucket.com/user/SpeedyGoomba/media/6016A820-7C85-4F0F-B9BD-4907BAF24D92_zps5y3umvms.jpg.html)

Two of these gauges never hop out of a cut or chase the grain.

[Graham Haydon]

Hi Brian,

Nice gauges, I'm quite partial to a basic pin marking gauge.

315143

[Brian Holcombe]

I like the cutting gauge because it can put a heavy mark, but the direction I was going with this is that the two gauges that stay in the cut very well have blades that are out of parallel (purposefully). The plus of the other two is that they can be used in any direction.

[ian maybury]

Nicely teed up Brian.

It all leads towards the point that there's right and wrong ways to grind a cutting gauge knife - that the various angles and so on matter. There may of course be more than one configuration that works well (David C has written about and recommended grinding away the side of the point on a traditional Western point equipped gauge so that it comes close to cutting), but looking at my Matsui and the shaping of the knives on it and on other Japanese marking gauges there's clearly been a bit of thought put into the grinding - which seems to be pretty standard. (i'm presuming it's one of the two that work well for you)

Next up for me is to sit down and take a close look at it and try to figure out what they set out to achieve, but maybe you are up to speed on the topic/can fill us in Brian?

[Derek Cohen]

Graham, the pin may be less prone to error, but it can leave a terrible finish across the grain. There is a good reason why many pins are converted to knives. And then the game changes - an out-of-square knife will leave a thick, rough line.

Regards from Perth

Derek

[Graham Haydon]

I agree Derek, I'd never use a Pin gauge across the grain, a marking knife and a square or a cutting gauge would be used there. As you rightly point out once you convert to a knife there are more issues but in my frame of reference once you've filed a pin you've got something closer to a cutting gauge. That's why I was interested to find out what type of gauge the op was referring to.

Brian, nice points. If I was to sum up marking gauge accuracy it would be that it should apply the same consistent marking each time. I had a quick look at the gauges in our workshop and they are all out of square to a small degree. They all apply consistent markings. Just checking a gauge with a square and declaring it faulty could be a touch unkind.

[Brian Holcombe]

Nicely teed up Brian.

It all leads towards the point that there's right and wrong ways to grind a cutting gauge knife - that the various angles and so on matter. There may of course be more than one configuration that works well (David C has written about and recommended grinding away the side of the point on a traditional Western point equipped gauge so that it comes close to cutting), but looking at my Matsui and the shaping of the knives on it and on other Japanese marking gauges there's clearly been a bit of thought put into the grinding - which seems to be pretty standard. (i'm presuming it's one of the two that work well for you)

Next up for me is to sit down and take a close look at it and try to figure out what they set out to achieve, but maybe you are up to speed on the topic/can fill us in Brian?

Indeed, the Matsui is my best gauge (in terms of precision movement and ease of use) followed by the Kinshirou and then the BS and LN. My thoughts are that it drives the gauge into the reference edge, making for a very easy and accurate way to cut a line. I like the Blue Spruce and LN gauges as well, but they're not as certain.

There is also something nice about a wooden face without brass inserts….wax it once and it stays waxed for a very long time. The wax moves into the grain rather than remaining forever on the surface and needing reapplication. This contributes to a nice and smooth cut.

The LN is my only panel gauge and so I actually use it with the pencil end more than anything else, and the BS I like for cutting across the grain. It doesn't work better than the Kinshirou or Matsui, but it works very well and does it's best work across the grain.

The reason I have a bunch of gauges is that I set them for certain projects and leave them that way until I no longer need them.

[ian maybury]

Ta Brian. Just had a look at my own Matsui and it seems set up much like yours - the knife has a single sided double bevel point much like a classic hand held two edged/single bevel sharpened/V point marking knife held vertically, but the line of the blade is tilted out a few degrees.

If as is presumably intended it's pushed in the direction that causes this blade tilt to result in the fence/head being pulled into the guiding edge of the work (pushing it the other direction would result in the fence/head being pushed away - which wouldn't be so good) this means that the beam/knife is placed well back towards the rear of the fence. Only 1 3/4in or so forward of it in fact.

Which means that the knife will hold that end of the fence from being levered away from the guiding edge of the work by the pivoting/rotating effect of the drag while it cuts. Then there's the relatively long almost 3in of fence ahead of the knife which will resist any tendecy for the same drag/rotation effect to push that end of the fence into the work, or more likely to pivot the gauge about the leading corner of the fence.

It's easier understood than described, but there's quite a cunning force balance in play that as you say stabilises the gauge as it cuts. (provided it's cutting in the right direction)

It'd be interesting to see how the same guys might tackle the layout of a cutting panel gauge - it's a rather more difficult problem because of the much longer beam. I'm guessing they would use a similar layout, but it might need a bit more care in use.

I guess a pencil is the ultimate direction insensitive low drag marking device….

[david charlesworth]

Offsetting the knife of a cutting gauge, is a cunning and effective plan!

I feel sure that brass strips are just "bling" for most tools and serve no practical use, other than to increase the price of a tool.

David

[Jim Matthews]

The Kebiki design draws the face tight to the reference edge.

They're not for everyone. The wheel gauge is a good choice for delicate work.
I like my wheel gauges for the bottom of dovetail tails.

I can stop and start so that the line is only where I need to cut away waste.

That's cross grain, by nature and won't wander.

When scoring a panel for thickness, you can't beat a marking gauge
that pulls itself tight - where the Kebiki excels.

[Tom Vanzant]

With any of the cutting wheel gages, it's important that the fence rides the square edge and only the wheel contacts the surface. It the wheel AND stem contact the surface, the fence is no longer square to the surface and tracks along the lower edge of the workpiece. Bad things will happen, especially with marks near the edge.

[ian maybury]

I guess a wheel gauge is normally set up so that the cutting disc is parallel with the fence. It's always hard to know how stuff works until we get the chance to try it out.

The issue with stuff like the 'toe out' on the Matsui/Kebiki type i suppose is that (while very useful) the precise setting has to be a bit of a one size fits all deal - the particular angle/degree of 'pull' may not be ideal for every job, or to everybody's taste.

:) Wonder if anybody has done an adjustable gauge? It wouldn't be hard to set up the V pointed knife variety that way. It could easily be made reversible so it could be used to cut in either direction as suited too.

A wheel gauge could be designed to deliver a similar effect by mounting the wheel at slightly oblique angle instead of square at the end of the bar - rotating the bar to a new position in the fence (which could be marked) would adjust the toe-in from zero to some max in one direction, to zero, to max in the other to zero again. One downside would be that it would always be cutting on the same arc of the wheel if it was always used at the same toe-out setting - which might shorten wheel/blade life a bit...

[Graham Haydon]

It's easy to see we all have our personal favorite way of applying a mark. I actually found my cutting gauge was my most inaccurate gauge by some degree. It still worked very well https://www.youtube.com/watch?v=e5LfDtSspVs

[Derek Cohen]

Hi Graham

Nice video!

As you pointed out, a single point is never going to be a problem with accuracy. Also, variations did not affect your cutting gauge.

In my opinion, an off-square beam/fence is not the issue with a cutting gauge, and it should not affect a point either.

The important factor with a cutting gauge, as I see it, is a constant edge direction, with the flat back of the blade parallel with the fence. Here is one I made from a HSS twist drill ...

http://i13.photobucket.com/albums/a262/Derek50/Marking%20and%20Measuring/Cutting%20guiage/gauges4.jpg

The line became ragged when the blade was out-of-parallel. I ground a groove for a screwdriver into the top edge to turn it into the ideal position.

Regards from Perth

Derek

[david charlesworth]

Have to disagree Derek.

You see in Grahams video how depth of cut with the pin gauge is achieved by pivoting the stem, from its front edge.

If this edge is significantly out of square, the problems which I described earlier, start to occur.

I am referring to squareness in the vertical plane, not horizontal.

Best wishes,
David

[Derek Cohen]

I am referring to squareness in the vertical plane, not horizontal.

Hi David

My comment was about the horizontal plane, that is, tracking the knife parallel to the face of the fence.

Regards from Perth

Derek

[ian maybury]

Hi Graham. Just picked up the Devon connection. It was about 20 years ago now (scary), but i several times did the Exe descent canoe race. There were two years in particular where there has been lots of rain, and the river was as we say 'tanking'. It gets quite hairy.

One thought regarding the out of square fence issue, primarily in the respect of a fence being out in the vertical plane. I'm not sure how likely the situation is to arise, but i guess one caution (coming from an engineering background) is that the situation may eventually arise where it gets used differently to normal, or the work ends up referencing off a different part of the face....

[Graham Haydon]

Nice gauge Derek and thanks for watching my efforts. I'll have to get around to making a gauge one of these days.

Hi Ian, I would of be 14 years old then :D. We do have "issues" with rain but the past few years have been kind. I'm up on the Northern Coast, not so far away from David Charlesworth. If you ever find yourself here again you'd be welcome to stop by our shop.

I think if the tool was able to reference differently each time there could be issues, hence why tools that can need to be highly engineered? All I know is my work even though they are simple :-).

[david charlesworth]

Derek, agreed! There is more to this gauge thing than meets the eye!

David

[ian maybury]

:) It's been a dead interesting thread actually for somebody like me just getting into the topic of gauges. Some great prompts of the sort so useful to thinking stuff like this through - even if it risks getting set back to zero upon contact with reality...

You never know Graham - i'm hoping to get over to the UK with the car this year.

[Warren Mickley]

Have to disagree Derek.

You see in Grahams video how depth of cut with the pin gauge is achieved by pivoting the stem, from its front edge.

If this edge is significantly out of square, the problems which I described earlier, start to occur.

I am referring to squareness in the vertical plane, not horizontal.

Best wishes,
David

It sounds like you are rubbing the stem of the gauge on the work piece as you mark your line. I used this technique for 8 years or more, but then in 1978 I realized that the stem had developed wear from this rubbing, especially in the first inch or two. So I started marking with the stem slightly removed from the work. It was a little awkward at first, but of course after 37 years I use it with more assurance than before I changed. I replaced the stem a few years later and now have one without wear. Maybe others just repace the stem or get a new gauge.

[david charlesworth]

That is an interesting modification of technique.

David

[Jeff Ranck]

From Brian's experience:

the two gauges that stay in the cut very well have blades that are out of parallel (purposefully).

From Derek's experience:

And then the game changes - an out-of-square knife will leave a thick, rough line.Derek

I think you are both talking about the same "out of square" plane - Horizontal. My suspicion from the rest of the thread is that the difference in experience is the difference between the JP knife gauge and how it is sharpened vs. Derek's "football shaped pin knife" which is what I think he's talking about.

If I've gotten the context of Brian's and Derek's comments right, then it seems like there is a dependency not only on the knife vs. pin, but also on the shape of the knife and how it is sharpened. So maybe Ian's comment about a right way and a wrong way to grind knives is more a right way and wrong way for a particular type of knife gauge.