Thinking out loud...... Thermodymics vs woodworking precision measurement tools?

[Joe Mioux]

OK, I am sitting in my garage consuming an adult beverage and looking at a TSO MTR-18 Triangle. It's 89* don't know the humidity.

My garage is heated, but not air conditioned.

My question. How does change in outdoor temperatures affect the accuracy of these types of tools (i.e. Starret (sp), Woodpecker's, TSO, et al measuring devices)?

I am also interested in reading the extent woodworkers go to achieve machine accuracy...

Temperature affects metal. how do we protect our high dollar measuring instruments? OR should we just buy a good quality framing square, bone up on our high school trig?k

Hoping for some fun and interesting commentary...

[Bill Dufour]

Outdoor temp has no effect on the stuff inside. In metal working you use gloves to handle the measuring instruments so body heat does not effect them. Accurate metal measurement is done and calibrated for a given temerature.
Wood moves with humidity and temperature. Humidity is far more important for wood movement. Humidity has no effect on metal unless it causes rust. Much metal working is done with flood coolant to keep the cutter cool and a little bit to keep the work temperature stable.
They worry about sunlight from a window affecting measurements. Big telecopes are mounted and aligned for a certain temperature, obviously one that occurs at night. Takes several hours after sunset for things to stop moving too fast to be useful.
Entropy says all the energy pumped into the shop is turned to heat unless some light goes out the window or the dust collector and sand blaster is vented outside.
Today my shop is about 101, the walls on the south side are 105 and the underside of the roof is 130.
Bill D
Bill D

[Edward Weber]

My short and sweet answer is this.
Yes metal moves due to thermal expansion but the amount it moves is so minute, in terms of a hot or cold garage, that it's a non issue in a woodshop. I would suspect that your high end squares will read the exact same thing in summer as in winter.

[Brian Holcombe]

The certs are done at 68 degrees, iirc.

[Andrew Hughes]

I’ve noticed the lips on my jointer sit slightly proud during the hottest months in the summer. When it’s 100 degrees plus. My shop is uninsulated my jointer is pretty large the tables are good cast iron and the lips are just regular steel.
I’ve not noticed any variation in small handtools.

[Mark e Kessler]

Actually some of our cnc machines are totally enclosed and conditioned as we found even with controlling the coolant temp we were still seeing dimensional changes with the tooling, bed, ect…

[John TenEyck]

Maybe Bridge City or one of the other companies that offer over the top priced tools will produce some Invar measuring instruments. You heard it hear first.

FWIW, plastic drafting triangles are almost always dead on with their angles, at least the Staedtler ones I have are.

John

[Paul F Franklin]

A 316 stainless steel scale, 12 inches long at 50 degrees, will be about 12.0008 inches long at 100 degrees. (using the engineering toolbox thermal expansion calculator)

Do machinists have to worry about that? A lot of the time they do. Do woodworkers? Well, not this woodworker ;)

Figuring out what happens to something like a 45-45-90 triangle is an exercise left to the reader (which is what my professors used to say when they didn't know how to explain something :D)

[Doug Garson]

I would expect the variation in measurements due to expansion or contraction of metal rulers in a woodworking shop would be insignificant compared to the expansion and contraction of the wood itself with moisture content especially if all components are cut and assembled under similar conditions. I assume the 89* you refer to is temperature (I hope in F not C :eek:), when I first read it I thought your triangle was one degree out of square, that would be a whole new issue.

Just to take this one step further, I've often wondered about large machinery components that are built in a shop, shipped thousands of miles to a jobsite sometimes in a different climate and then assembled along with other components built in other shops. I remember working on a jobsite where a large ship loader was being assembled and seeing the main body bent like a banana because the sun was shining on one side and the other side was in the shade.

[johnny means]

At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.

[Richard Coers]

Thermodynamics deals with the relationship between heat and other forms of energy. Coefficient of expansion is the change in dimension of different materials due to temperature change. I really don't understand how trig comes into play here either. Calculating the angles and side lengths of shapes has nothing to do with temperature change.

[John C Bush]

I think the most significant concern in your situation is the thermal impact on your adult beverage. Prudent management would be limited time exposure to the (external) elements using the bottoms up protocol!

[Doug Garson]

At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.
I suggest you put your measuring tools in the fridge when they reach 80 degrees F , take a few brews out to make room if necessary. That way when you get back from fishing they will be cool enough to use. :D

[Curt Harms]

At about 80 degrees Fahrenheit all my measuring tools become unusable. But fishing gear reaches peak utility. It's best to schedule accordingly.

:D



10 characters

[Mark Hennebury]

Accuracy is more of a mindset than a toolset!

It is about:

Knowing the variables
Understanding the relationships between parts.
It is about knowing how to check and reference parts.
And developing a process to check and verify.
And having the discipline to follow your process.

Expensive tools wont give you this.... Beer may help.

[Kyle Iwamoto]

Expensive tools wont give you this.... Beer may help.

:D
I think wood moves more with temperature than your Starrett.
Enough beer will either make you not see the error or not care about the error.

[Bill Dufour]

I assume you have all your measuring equipment recertified at least once a year? You do use a pull scale for your measuring tape don't you? How do you calculate for sag when using a measuring tool in the horizontal position? I know there are published tables for wire sag for measurements at various temperatures.
Story is the survey party that early on surveyed the us canada border made some mistakes. The us crew stayed sober and gave as much alcohol as possible to the canadians. It paid off in a little extra land here and there.
Bill D.

https://en.wikipedia.org/wiki/Tape_correction_(surveying)

Better then invar?
https://www.compositesworld.com/articles/carbonbmi-and-carbon-foam-form-invar-alternative

[Scott Clausen]

I know this is a thing for metal work. Working with wood once my initial layout is done via tape rule everything after that is relative to another part or story stick. It is consistent because I just let the air conditioning run 24/7, keeps the beer cold longer too.

[Brian Holcombe]

Precision always matters, accuracy sometimes matters and sometimes accuracy and precision matter.

[Bill Dufour]

For me repeatability is far more important then accuracy. I do not care if the piece is 36" long or 36.05. as long as they are all the same. Do they still balance pistons at the factory by grouping them together in similar weight classes?
Bill D

[Brian Holcombe]

Bill, repeatability otherwise known as precision. :D

[Ken Fitzgerald]

When I am drinking beer, ( my preference is a locally brewed Scotch ale) I never worry about or handle tools or do any measurements. Typically this deaf guy prefers to put on some cordless headphones, put on some late 60's or early 70's rock and ROCK ON!:D

[Mark Hennebury]

For clarification,

as I see it, you need both accuracy and precision. Maybe in different pars of a job, but you need both to make it work.
In woodworking you don't have to worry about high tolerance specifications. But you do have to do high tolerance fit of components.

In woodworking you may not care if your dado is 0.750" or 0.755" but you have to have accuracy when you dress your panels to have them fit, and you have to have precision if you want all of them to fit.
If you want to cut all of your mortises 0.500" ( your target measurement)
and they end up being 0.510" you don't have "accuracy" in that you have missed your target measurement. But you have precision because they are all the same size.
So now your need both accuracy and precision to complete the joint.
When you cut your tenons. Your tenons need to be accurate in that they need to be, for example 0.510" ( or whatever fit you decide)
plus you need precision for them all to be consistent.
And of course no one cares if you make a table 60" long and it ends up 59.95" So you may not need accuracy in this part.
But for the overall job you need both accuracy and precision, and to know when and where to apply them.

[David Buchhauser]

A 316 stainless steel scale, 12 inches long at 50 degrees, will be about 12.0008 inches long at 100 degrees. (using the engineering toolbox thermal expansion calculator)

Do machinists have to worry about that? A lot of the time they do.

I can't imagine even the most skilled machinist or tool maker using a steel scale (rule) in a situation where 0.0008" deviation would come into play.
These type measurements would more likely be done with a micrometer or height master. I personally use the Mitutoyo Height Master on a Starrett granite surface plate for critical measurements. My Height Master has a resolution of 0.000010".
David

[Mark e Kessler]

moldmaking, HotRunners specifically - Where I work at my day job we regularly machine and hold +- tolerances of 5microns (a little less than 0.0002in) I believe we have some components that are even 1/2 of that…



I can't imagine even the most skilled machinist or tool maker using a steel scale (rule) in a situation where 0.0008" deviation would come into play.
These type measurements would more likely be done with a micrometer or height master. I personally use the Mitutoyo Height Master on a Starrett granite surface plate for critical measurements. My Height Master has a resolution of 0.000010".
David

[Mark Hennebury]

A simple no tool method to check fence and blade setups for high precision crosscuts.


Take a couple of pieces long straight square stock and mark the face and edge on each one.
Trim the ends off of two sticks.

Stand them up on a flat surface. slide them together, with the faces facing the same direction see if they fit. Rotate one 180° check again. That's it!
Repeat the process to check the edges.


This will tell you if they are square to a much higher degree; much easier to see and measure error, then checking the end with a square. And it tells you square in both planes.
This is the most accurate way to check your miter-saw fence, table-saw fence, sliding table saw etc. It tells you if the fence is square to the direction of cut, and if the blade is square to the table.

The longer the sticks the more you will magnify your error. For instance if you use 2"x2"x 50"long you will magnify your error approximately 48 times.
one quarter of a degree off of square on a 2x2 measure about 0.009" but at 50" it measures 0.218 and this method will double that error to 0.436 gap at the top of your two sticks. So it is easy to see minute error in your fence or blade setup-up.

By doing a few test cuts and adjusting your fence until the gap disappears you can obtain a very high degree of accuracy with no tools.

This is similar to a high precision reference cylinder square method.
You could also use round plastic tube if you want.
461332

[Bill Dufour]

To build the pyramids they needed a good level. So they built a wooden trough around the job site for reference. Had a boy or two keep it filled with water to a mark at all times. Worked very well. Definitely better then in Piza, Italy using more modern tools.

[Mel Fulks]

To build the pyramids they needed a good level. So they built a wooden trough around the job site for reference. Had a boy or two keep it filled with water to a mark at all times. Worked very well. Definitely better then in Piza, Italy using more modern tools.
But the Piza logo has been much more successful than the Camel cigarette logo

[David Buchhauser]

moldmaking, HotRunners specifically - Where I work at my day job we regularly machine and hold +- tolerances of 5microns (a little less than 0.0002in) I believe we have some components that are even 1/2 of that…


I can hold 2/10ths (0.0002") or better as well with both my Nakamura Tome and Matsuura cnc machines. But I'm not using a steel rule/scale to verify this.
David

[Tom Bender]

The tower in Piza was built straight in the first effort (about half way) then the project stalled for some time, during which the ground settled and the tower tilted. When someone continued the work they built straight from there. It continued to tilt until recently when it was straightened up. Now it is the crooked tower of Pisa.

[Jim Dwight]

I think the accuracy has already been accurately stated but I will add my 2 cents anyway. Metal moves with temperature but not enough to matter at temperatures our body can tolerate. I looked up a thermal expansion coefficient (googled it) of 13% per degree F but that is 10 to the negative 6 for aluminum. In other words .00000013 times the length. Steel is 6.7% - about half. So if you really care, use steel measurement devices not aluminum. But neither moves enough to matter.

A square built of the same materials will not become un-square due to thermal expansion. All the material will move exactly the same amount. If built of dissimilar materials you could do the math but I am pretty sure it also won't matter.

This is physics, not thermo dynamics - but that also doesn't matter.