In search of accurate measurements

Help me understand.

I see 5 lines between the 1 and 2 mark, including the 1 mark. If I count the edges, 2 per line, I count 9, and the 10th would be the next mark. Based on that counting, it is not a vernier scale.

It looks like the 1 mark lines up with 11 mm; the 2 mark lines up with the 21 mm, the 3 mark lines up with the 31 mm, etc.

I must be mis-interpreting this.

I think you are trying to read it as if the parts that stick up are the markers,
when it’s the gaps between them that are the markers (you look for the line on
the tape measure in the slot)

there are several configurations available now

in every case, the ‘0’ mark is not shown on the left side and would be centered
exactly 1mm from the end.

0.01mm has small ticks every .99mm and large ticks (and numbers) every 9.9mm, so
when you add the 1mm offset, the last gap should line up with the 10cm (100mm)
mark.

0.02mm has small ticks every 1.98mm and large ticks (and numbers) every 9.9mm,
so the same total distance as the 0.01mm version, just with larger spaces
between the lines

0.05mm has small ticks every 2.95mm with large ticks every 5.9mm (with the final
gap at the 6cm mark on your tape)

0.05mm tight has small ticks every 1.95mm and alrge ticks every 3.9mm, it lines
up with 4cm at the end, but the numbers may blur together (depending on your
printer)

0.1mm has small ticks every 1.9mm and no large ticks or numbers

0.1mm wide has large ticks every 3.9mm with numbers

and there is a 3dtest version that doesn’t print to full height and has spacing
between the gaps of 1,2,2,1,3,3,1,2,2,1 mm. It’s designed to let you quickly
print something out that you can tweak settings with to see how tight a
resolution you can get and to tweak the dovetail to fit nicely and the pin to be
exactly 6.35mm diameter

David Lang

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Good work guys, this looks like a great little tool. Do you feel like it is ready for community use or are you still tweaking things? I don’t have a 3D printer and would be interested in purchasing from someone.

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I’m pretty happy with it, I think it’s ready for wide testing at least.

For my eyes (and available 3d printer), I am thinking that the 0.05mm version is
about the sweet spot of accuracy vs ease of use. I’d really like to have some
other people try it.

I haven’t yet investigated what it takes to post a design on thingiverse,
especially one with multiple options/configs available. I know I’ve seen people
do it, but haven’t looked at what it takes.

There are various services that let you upload .stl files and they will print
them for you, I would suggest contacting some of them and sending them a link to
the onshape document, asking them about details like how accurately a part
that’s in the model at 1/4" actually translates to 1/4" in the real world.

On my printer, simply changing the filiment with no other changes resulted is
differences in that 1/4" feature size that were significant. I created the3D
test version to have something that would print much faster (15-30 min vs
several hours on my printer) and let you check your machine’s results.

David Lang

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The link in your first post is the latest / greatest?

This is what inspired this project. If anyone knows where to buy one of these, please let me know.

Here is an image of the .02mm version. This shows that the end of the tape is short by .42mm (it’s showing the line matching the slot at .58mm, but if you look at the 0 at the end, you will see that it’s past the 10cm mark, so ‘0’ on the tape is actually .58mm past the 1mm mark on the tape

This is a 0.1mm version showing the pin at 209.9mm

This is the 0.05mm version showing the pin at 131mm (we don’t quite have the right camera angle, but it looks like the line matches at the ‘0’ mark)

This also shows the test piece in the forground, it shows the pin spacing needed for various versions and is fast to print so that you can fine-tune the pin diameter/length, the dovetail fit, and the width of the lines.
There is a very short pin to the left of the 1, to the right of the 5, if they work well, you can print the 0.01mm version, if you have good pins between the 1 and 2 you can print the 0.02mm version, if they don’t work, you have the pins to either side of the 3 and have to stick with the 0.05mm or 0.1mm versions

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it still gets you to the document, but gives you an error since the tab no
longer lists. Here is the updated link

https://cad.onshape.com/documents/6ad35fdba3e3babde64e604a/w/a26beded4d7ab9aea561ab08/e/98faa5467fe149a4529f83e0

at the very top left there is the vernier accuracy configuration that will let
you select the version to use.

you need to clone the document to be able to set the variables for tuning the
pin, lines, and dovetail.

David Lang

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That looks like the back end of a standard vernier caliper with the front removed that’s been slid over a tape measure.
we could probably use something like this, it’s not going to be as accurate as a starrett, or other high quality caliper, but as our primary scale is a tape measure, it probably doesn’t matter, provided the tape measure can be made to fit snugly in the slot.

@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.

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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.

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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

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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

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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.



I’m not sure why the peg didn’t come out round but the resin print is very nice.

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