@dlang, found it…
EDIT: …and I believe this is closer to the caliper that TomD has (looks the same except the marks are different):
https://www.amazon.com/Stainless-Micrometer-Measuring-Precision-Measurements/dp/B074HZ8S21?ref_=Oct_TopRatedC_2476630011_2&pf_rd_p=6ad10c7f-6614-585b-99d6-9e53eaed0571&pf_rd_s=merchandised-search-6&pf_rd_t=101&pf_rd_i=2476630011&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=FSWD0ASD8A04V2JZ2M5S&pf_rd_r=FSWD0ASD8A04V2JZ2M5S&pf_rd_p=6ad10c7f-6614-585b-99d6-9e53eaed0571
I once looked for “vernier tape measure” on Google and found this site: https://verniertape.com . However there’s no apparent way to order that (rather expensive) product, and an inquiry to their “contact us” page got no reply.
Cool product! Lots of 404 errors from the site makes me feel like the business might have went under. Not even Amazon has their product! I’m surprised there isn’t someone else doing this.
That is an interesting site, they did a more complicated version than I’m trying. They apparently did it to 0.01"
I can see why there would be a lack of demand for it, especially at the cost that they probably had it at.
It’s just the back end of a caliper.
The link I posted are cheap plastic calipers, but they could probably be separated easier: with a metal caliper, you have to remove the endstop and screws in order to take it apart, usually the plastic calipers just slide apart, and they are super cheap. There is a small loss of accuracy, and the numbers can rub off if they are just printed on, but the stainless steel calipers from china are going to be about the same accuracy as the plastic ones, and with us using a tape measure as our primary scale, the accuracy will already be compromised slightly.
I like @dlang ‘s idea better since it has a nipple on the back that would stick into the six hole calibration holes. That should help with inconsistency and in accuracies with the way a tape measure might be anchored to The hole. I also liked @Joshua ‘s idea of making those holes deeper so that this kind of tool can be inserted in so that it is only a one-man job to measure with vernier scale on the other side.
given how slow the Z axis is, I would also reduce the ‘safe height’ in the
g-code file.
I have the length of pin adjustable so that it can match the hole, I had assumed
they were 1/4" deep, but now that I see they are 5mm, I’ll shrink the pin by
default
I found a new option for the configuration options, so I changed the variables
from being something that you have to clone the page to use to something that
you can change without being logged in and then export the result.
even without the square support peg on the end and with an over-long pin it
works pretty well for a one-person measurement (as long as your arms are long
enough to reach both holes).
you either want the dovetail a little snug, or you want to put a rubber band
around it to keep it from falling off the tape measure. When measuring, it’s
easy to have the end of the tape get a little loose and not get a fully accurate
measurement at the end.
David Lang
I posted this to thingiverse so you can order them printed.
I’ve ordered versions in resin, PLA, and ABS and will report how they come out
when I get them.
David Lang
A friend of mine is printing the 0.05 version with resin. Should have it next week sometime. Will report back!
Also, he said his resin printer build volume is 115 x 65 x 155mm but it has an accuracy of 25um!
EDIT: final product is very nice! Haven’t used it yet, still making other frame mods.
Would you have a recommendation for a tape measure to go with that? I suspect I will have to order the tape measure too, here in imperial-tape-measure-land.
any tape measure with metric. Here in the US you can easily find ones that have
both Imerial and Metric. you want one with metric on the bottom and 0 on your
left (otherwise I need to make a mirror version)
I like wider tape measures, but this is designed to handle any width.
If you print one of these out, take it in when you buy a tape measure and see if
you can find one that is exactly correct (the 0 on the vernier scale is exactly
at a cm mark), that way you don’t have to account for error on the 0 end as you
measure (this is just a nice-to-have, but it’s a very nice, nice-to-have)
David Lang
Guys! I apologise for stirring this discussion but we should abandon idea of tape with vernier. I think that we are barking wrong tree.
Read this:
and my respond
and my response:
When I was a teen I wrote a short paper for science class regarding how any measurement is an approximation.
I guess the only way to decide how close to accurate a tape measure is, is to use an object with a known length and check the variance between that object and your tape.
Wait a minute!!! If all parts of my project are re-scaled to measure tape with 2mm ABSOLUTE error that’s OK! I need resolution - I do not care if my boat IS 5000mm long measured with one tape or 4998mm using another tape. When assembling parts made by my Maslow all what I care is how precise they fit to each other - and this is RESOLUTION.
I AM CALLING OFF MY PREVIOUS POST! TAPE WITH VERNIER IS NOT STUPID IDEA!
After this discussion about tape accuracy, and seeing how far off some common tapes are, I’m starting to think that we should start thinking about including a class 2 tape (and possibly a couple of these vernier aids, and possibly a level) in the kits, increasing the cost of the kit just a little bit.
I have a couple of these that I’m happy with ($10 each) https://www.rockler.com/fastcap-procarpenter-standard-metric-tape-measure
Stanley tape measures are class 2 as well.
all of them?
we need a tape that has metric on it, and for folks in the US, I think we should
also have imperial (the tape I linked to has both)
David Lang
@dlang I recall reading about a stick or dowel to use for making manual calibration marks. That gave me an idea.
For measuring Holey Calibration, what if we could fabricate two laser cut, concentric, stainless tubes (tube within a tube like a curtain rod but much better!) that have laser etched mm scales at each end. Each end would have a slightly tapered 1/4" nipple to snug fit into the drilled holes. I realize this could be expensive but if (when 
) Holey becomes stock, maybe a supplier (cough, cough, ehm @Metalmaslow) could find a place, or an alternate design that is reasonable at relatively large quantities.
you still have the problem of how to go sub-mm
the result will be fairly long (remember you are measuring from ~700mm and
1300mm on a stock machine, smaller on smaller machines, larger on larger
machines)
I don’t see this as being any cheaper or more accurate than a class 1 or class 2
tape measure (especially when combined with something like the 3d printed
vernier adapters)
David Lang
