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Re: stanley tape measure accuracy

#260496 by BuckeyeDennis » Fri Jun 14, 2019 9:43 am

dusty wrote:What level of accuracy is reasonable to expect of a ruler or tape measure that is marked in increments of 1/16" or even 1/32".

1/16" = .0625"

1/32" = .03125"

If expecting measurement accuracy at the .005" level I hope you are not marking the cut point with a lead pencil.


That's a very good question, Dusty. Aside from very expensive rulers, I haven't found any with published accuracy specs. So you get what you get, and then you have to calibrate it yourself.

As for accuracy vs. resolution, it's real easy (assuming good near-field vision) to interpolate a measurement halfway between graduation marks. That would be the minimum acceptable accuracy to me. Interpolating to 1/4 of the smallest graduation isn't difficult either.

That said, I'm not a typical user. I have one eye that is very nearsighted, so without glasses it acts like a magnifying glass up close. I can easily see individual pixels on a 300 DPI printout -- those would be about 0.003" wide.

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Re: stanley tape measure accuracy

#260497 by RFGuy » Fri Jun 14, 2019 9:48 am

thunderbirdbat wrote:While some tape measures are checked for accuracy, none of the ones I have seen were. The tape measure is marked with roman numerals when it is checked for accuracy. Here is a decent descriptions of the makings found on a tape measure. https://www.thetapestore.co.uk/knowledgebase/How/Tape_Measure_Markings_%E2%80%93_What_Do_They_Mean_.html

Thanks. Interesting article on tape measures. I wonder how far the ratings extend outside of the UK, i.e. if manufacturers follow this outside UK. I have never seen a tape measure with these accuracy markings, but I will have to check out the hardware store to see if any newer ones have them.

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Re: stanley tape measure accuracy

#260498 by BuckeyeDennis » Fri Jun 14, 2019 10:00 am

thunderbirdbat wrote:While some tape measures are checked for accuracy, none of the ones I have seen were. The tape measure is marked with roman numerals when it is checked for accuracy. Here is a decent descriptions of the makings found on a tape measure. https://www.thetapestore.co.uk/knowledgebase/How/Tape_Measure_Markings_%E2%80%93_What_Do_They_Mean_.html


Thanks Brenda, that's great info! And it pretty definitively answers Dusty's question about how much accuracy to expect in a tape measure. Neither of my "good" tape measures are marked with an accuracy class, so they are presumably not rated for accuracy. I might just have to order a Class 1 tape from that outfit. Especially if I can get it with dual metric/imperial markings -- that could be real handy.

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Re: stanley tape measure accuracy

#260499 by RFGuy » Fri Jun 14, 2019 11:23 am

BuckeyeDennis wrote:
thunderbirdbat wrote:While some tape measures are checked for accuracy, none of the ones I have seen were. The tape measure is marked with roman numerals when it is checked for accuracy. Here is a decent descriptions of the makings found on a tape measure. https://www.thetapestore.co.uk/knowledgebase/How/Tape_Measure_Markings_%E2%80%93_What_Do_They_Mean_.html


Thanks Brenda, that's great info! And it pretty definitively answers Dusty's question about how much accuracy to expect in a tape measure. Neither of my "good" tape measures are marked with an accuracy class, so they are presumably not rated for accuracy. I might just have to order a Class 1 tape from that outfit. Especially if I can get it with dual metric/imperial markings -- that could be real handy.

FYI...I had an errand to Home Depot this morning so I did a check on all the tape measures there (Milwaukee, DeWalt, Stanley, Ryobi, etc). None of them have markings for class I, II or III, as I suspected. I would guess the major manufacturers that sell these in the USA are either class II or worse for accuracy, which shouldn't be a surprise since tape measures are intended for rough carpentry (unless they are survey tape measures). On this website, the only brand that comes up when you select class I accuracy is the Fisco brand by the way, so that may be the only option if you want a more accurate tape measure.
Last edited by RFGuy on Fri Jun 14, 2019 12:47 pm, edited 1 time in total.

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Re: stanley tape measure accuracy

#260502 by Hobbyman2 » Fri Jun 14, 2019 11:40 am

one method I have used for years ,,when possible ,,,is to attach a 3ft steel rule to the bottom of the work bench and a smaller one { 2f } at 90deg vertical with zero on each butting at the corner just like a carpenter square , allows me to make angles , layout lines and draw patterns accurately on the bench as well as mark stock and I dont need to hold anything while trying to mark a line with a square . my guess is you could do the same thing with a carpenter square ? I just prefer the rules do to their smaller graduations . jmo to the tape measure many time the hook can be bent to adjust the difference between two different tapes , however that doesn't mean they are accurate .

---

Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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Re: stanley tape measure accuracy

#260507 by wa2crk » Fri Jun 14, 2019 1:05 pm

As Norm Abram said,"when you start a project use the same rule for the entire project". This will eliminate the variations that come from varying manufacturers.
Bill V

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Re: stanley tape measure accuracy

#260508 by benush26 » Fri Jun 14, 2019 1:14 pm

Also another point that may or may not be relevant to those on this forum is that tape measures, even within the same model, are also not consistent in their errors. Case in point, a lifetime ago I had a crew making some forms for concrete work. When they were finished, each form by each worker was a bit off (about 1/4" in two dimensions which was not acceptable for that particular project). Turned out that each of the three tapes had a different distance for 16' :eek: . That night I went to a local supply shop and pulled all the 25' tapes they had (more than a dozen) and chose 5 that were sort of close at 20'. Three were by Stanley and the other two were by Lufkin or maybe it was 3 Lufkin and 2 Stanley?! I would have bought more, but of all those we checked, only those 5 were plus or minus a 1/16th of each other at 20'. How accurate their 20' mark was to a real 20' I don't know
I had my guys leave their tapes in their rigs and ONLY use the ones I bought. Painted the cases with an ugly fluorescent paint to distinguish.
I bought a flat engineering steel "chain" from a survey supplier that we used for everything that needed to be precise and even it was off a bit.
Sure I use a tape measure, but I've found that the cheapest is just fine for making a "close enough" mark. I still trust my wooden folder for precision (though maybe even it is off?)
As an aside, when marking something that requires good accuracy, I use a marking knife, instead of a pencil.
Just my 2 cents.

Be well,
Ben

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Re: stanley tape measure accuracy

#260511 by edflorence » Fri Jun 14, 2019 4:03 pm

benush26 wrote:I bought a flat engineering steel "chain" from a survey supplier that we used for everything that needed to be precise and even it was off a bit.

Be well,
Ben


I did some survey work back before the dawn of the Digital Age, using transits and steel tapes and one thing I remember from those days was that the steel chain had to be compensated for temperature and sag. You had to grip the chain with a device that let you know just how much tension you were pulling with and you had to take the air temperature. With that information, you could adjust the measurement shown on the chain. Maybe the measurements you got from the chain you were using needed to be adjusted for conditions.

For woodworking purposes, I have always found that most any measuring tool will get you close to the desired dimension. Close being say within a quarter inch or so, and then from there on the "cut and try" method will get you to the desired result. If you have a situation where you need a very specific dimension, you usually have a space for that piece to fit into, so you can cut a bit oversize and sneak up on the desired dimension, trimming and trying until it fits. If the piece does not have to fit into a particular size space, then there is more tolerance for dimension variations from the "plan" size.

On the other hand, if you really do want a tape you can trust, you might try this one:

https://youtu.be/9ovuFoiVwr0

I have the 3 meter one and it is marked with the Roman Numeral II. It is a totally different design than any other tape I have used; no play in the end piece, a brake that really works and very easy to read markings. However...I have not been able to find a Talmeter with English dimensions.

---

Ed
Idaho Panhandle
Mark 5 of various vintages, Mini with reversing motor, bs, dc3300, jointer, increaser, decreaser

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Re: stanley tape measure accuracy

#260520 by RFGuy » Sat Jun 15, 2019 7:41 am

Ed,

Thanks for the YouTube video on the Hultafor tape measure you have. It kept me entertained this morning while burning time from my insomnia. That looks like a very nice tape measure. I really like the diameter measurement capability of that tape and the circle marking. I guess Hultafors bought out Fisco (Type I tape measures), so they are combined now...

Also thanks to Ben for pointing out the variation from tape measure to tape measure. I wonder what kind of process is used for printing the marks on the tape measure. I am surprised there is so much variation, but it depends on the process they use to print the markings. When I get a chance, I'll have to compare my laser measure to my tape measure just out of curiosity. Again, I know the tape measure is intended, typically, for rough measurements, but "rough" is a relative term...

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Re: stanley tape measure accuracy

#260521 by dusty » Sat Jun 15, 2019 8:27 am

Maybe, since I don't know how the other comparisons were performed, my own observations are to be ignored. But, I compared three heavily used tape measures, (2 Stanley and 1 unknown) and they all agree to within <1/16".

Now I only did external measurements at 48" (using the hook). Why only at 48"? Because I hardly ever measure anything over 48" where precision is necessary.

I think this is a lot of fuss over nothing unless you have money to burn on "precision measuring devices". Call me cheap and practical.

---

"Making Sawdust Safely"
Dusty
Sent from my Dell XPS using Firefox.

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