Class (1) one tape measure

[Bob D.]

I don't know why there is all this worry over the accuracy of a relatively short metal tape.
Unless you're pulling that tape with some sort of tension gauge (calibrated of course) to
ensure you put the same tension on the tape every time AND you compensate for
temperature it's all pointless. And you're not building a watch so again what's the point.

If you want to dive into the deep weeds, get yourself some light reading. A little dated but it's a start.

Calibration of Line Standards of Length and Measuring Tapes at The National Bureau of Standards
https://www.govinfo.gov/content/pkg...VPUB-C13-4897c508a3a9e5e445c66591da704b30.pdf

Here's a couple snips from a Lufkin tape catalog. They don't even worry about calibrating short (

 

[Cheese]

That thermal compensation indicator at the end of the Lufkin tape is pretty interesting Bob...that's a new one on me.  [smile]

Rather reminds me of the Starrett shrink rules. [wink]

 

[Birdhunter]

If I am doing a complex jewelry box or other objects, I’d use a tape measure only for measuring rough cuts then turn to other tools and techniques for precision measurements. I’m ok with a “good enough” tape measure.

However, I don’t have a clue why I have 6 or 8 of the darn things around the shop. Might be I’m too lazy to walk around looking for my one and only tape measure.

 

[mino]

Folks, I think many miss the point of calibrating, or even using Class 1 tapes.

When making self-contained things like furniture. It is, indeed, not importnant if 10" real is 10" on tape. But is IS important that 4 pieces of 10" on tape when put one after each other are 40", at least on that same tape.

No standard will guarantee you that - only a -proper- calibration will. Class 1 tape in this case means at least the manufacturer did put some effort so you are 90% "OK".

Ref. the calibration procedure every 5' - I believe that is for long tapes, like 50' long etc. Indeed for a common 10-15' tape measure it would be too coarse to be useful. One needs a checkpoint every 1' or less for calibration report to be useful.

In practicals:
There is a huge difference if one makes stuff from laminated chipboard or from raw wood. Raw wood stuff moves, chipboard or MDF does not. And even tricks which allow raw wood to move are also not possible to hide imperfections there.

0.005" off over a 6' can easily be caused by a crappy tape and result in the furniture being unusable. The customer (wife etc.) will not accept it and re-edging may not be possible due to the fixed dowel positions etc. A completely different scenario to bespoke wood furniture which does not align by design.

Only using Class 1 measures, no to mention calibrated, in a wood shop, is indeed a case of OCD gone wild to the point of idiocy.

At the same, having a reference Class 1 tape (ideally calibrated where cost-effective) around is useful in every shop. If for anything, then to allow identifying crappy tapes or rulers when one buys them. Instead of making a mis-aligned product with them and then guessing what went wrong where in the end.

 

[hdv]

Hmmm.... maybe I am missing something here.  [huh]  Isn't all this just a bit too much for woodworking?  [blink]

I just compare all my measuring tapes and rulers to make sure they give me the same readings over a certain length. The "same" within reason, of course. The ones that differ too much are given away. I think I remember a post by someone else here on the FOG doing just the same.

I do have both Tajima and Hultafors class 1 tapes, but that's because the price for them was very good at the time. No "official" calibration or such. Just compared scales. Up to now that has given me good enough results. I see no reason to change this approach now. I don't really care about the exactness of the value, just that it is a value that will be he same over different measurements. I realise there might be non-uniformity in play. That's why I compare over a length, not just at a few discrete points along that length.

Some have suggested using just one tape measure during a project, but for me that isn't feasible. I have too many tapes that are fixed in place for that approach. Comparing tapes and rulers is more practical to me.

I was planning to find out if my "standard scale" would match the readings of my digital measuring devices, but haven't done so yet. I haven't had a compelling reason to be in a hurry with that.

 

[Michael Kellough]

It was good to see the thermal rule of thumb, 1/10th inch per 100 feet per 10 degree difference to 68 degrees f. That’s just 1/100th inch per 10 feet so at cabinet making scale it can be ignored. Crazy Race Guy does such large installations that he could detect a thermal difference but his shop and the places his work are installed in are probably temperature controlled.

Back to the difference between various tape measures. A couple of times I’ve compared a batch of tapes to each other and to a 3 foot Starrett rule. In one case there was more deviation between individual nominal 1/16” increments than the the 10 foot thermal deviation. I think it was a big Lufkin tape. That tape was exiled to the backyard shed for landscaping work.

Other class 2 tapes are distributed all around the shop for the convenience of finding things of the approximate right size to bring back to the workbench where the final measurement will be made with a class 1 tape or a precision rule.

 

[rmwarren]

This is great! It's not my fault things I cut are often the wrong size, it's the tape measure... [doh]

Works for me.

RMW

 

[Mini Me]

Hmmm.... maybe I am missing something here.  [huh]  Isn't all this just a bit too much for woodworking?  [blink]

Brian Holcombe is a woodworker of immense talent as his finished pieces will show and he wrote the following.
https://brianholcombewoodworker.com/metrology-for-the-cabinetmaker-introduction/

 

[Hotwheels]

Hmmm.... maybe I am missing something here.  [huh]  Isn't all this just a bit too much for woodworking?  [blink]

Brian Holcombe is a woodworker of immense talent as his finished pieces will show and he wrote the following.
https://brianholcombewoodworker.com/metrology-for-the-cabinetmaker-introduction/

That is a very useful read....

 

[Mini Me]

I should have added that he makes a living out of what he produces unlike plebs such as myself.

 

[MikeGE]

I should have added that he makes a living out of what he produces unlike plebs such as myself.

Brian is also a frequent contributor to Furniture & Cabinetmaking magazine with his projects.

 

[hdv]

Thanks. I will read that. It's always good to educate oneself more.

 

[alltracman78]

This is great! It's not my fault things I cut are often the wrong size, it's the tape measure... [doh]

Works for me.

RMW

Hahaha!
It's actually true. Years ago I was building MDF toy storage and I was using a Swanson 6 foot ruler because I thought it would be more accurate than my tape measures. All the pieces kept being out of square and not fitting correctly. Drove me nuts because I kept buying new panels and I wasn't able to get a single square cut. Then I had the epiphany to check the rule against my tape measure. Everything agreed at 6 feet (rule was mirror image, one side started at 0 inches while the other was 6 feet) but when I started looking in the middle it was off by over 1/4 inch in some spots. Say one side said 37 inches the other side would also say 37 but actually be 37 1/4 inches. I ended up ordering the Woodpeckers flat rule set. The Swanson is now relegated to a straight edge for scoring/lining.
Also goes to show the importance of checking all along the measuring device for accuracy.

This is a very interesting and fantastic book about precision if you enjoy that kind of stuff. One of the things it tells is how Jo blocks came to be (If you read the link above). I found it at the library and enjoyed it so much I ordered my own copy.
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