is it possible to improve this digital indicator? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2019, 02:49:45 pm
content: My fowler digimax indicator has this issue where if you displace it, and let it go back to zero, it reads an offset of around 0.002 mm.If you touch it gently (and I mean just touch with the tip of your pinky) it goes back to zero. Its like backlash and you need to poke it in the opposite direction it traveled to get it to spring back to zero. It has a screw on it that says do not adjust.Should I adjust it? is that normal for a tool that can read so small? (never worked with this) or sign of some kind of sticky gear or other defect?I am inclined not to fuck with it.

author: duak
author_rank: Super Contributor
timestamp: August 11, 2019, 06:00:08 pm
content: A friend runs a CNC machine shop where all the machinists use Mitutoyo digital calipers. The Mitutoyos always return to zero whereas my Chinese digital caliper does not. The Mitutoyos slide a bit easier and just feel a bit smoother, probably because they are made more precisely. I don't know exactly why there is a repeatabily problem but it's probably because of rougher surfaces and looser tolerances covered up with a bit of grease. I don't know if messing with it will help unless you can find out what the setscrew actually tightens up.This guy does some interesting things to restore/rebuild/improve machine tools:https://gtwr.de/stefan-gotteswinter-prototyping-tools-and-machines/I don't think he's rebuilt any calipers though. He used to have more stuff up on his website but it looks like it's been taken away.

author: coppercone2
author_rank: Super Contributor
timestamp: August 11, 2019, 08:07:12 pm
content: a caliper I can understand because its 0.001 inches, my fowlers work fine in that regard (I like fowler/slyvac tools).But this is 0.001 mm.. way finer then even the best caliper or on par with a micrometer.My mitutoyo micrometer closes pretty good, but its kind of a heavy mechanism with a clutch rather then this spring loaded dinky thing hanging out the side of a box.I wonder if I am expecting too much. I mean fowler is lower budget, but it is swiss. But its a0.000039 inch division step.I thought it might be within the limits of what can be done without a laser or something better then a spring arm.

author: coppercone2
author_rank: Super Contributor
timestamp: August 15, 2019, 06:25:42 am
content: ok, I think the problem was old grease. I thought I could get rid of the problem by dipping the tip in a ultrasonic cleaner for a bit and dripping 3-in-1 oil into it, but this made it worse after it sat for a few days (started offsetting by like 0.007) . So I dunked the tip in alcohol, ran alcohol stream over it, and gave it a good spray of silicone oil (wd40 brand) and exercised it and now the offset stays around 0.001 mm and only appears sometimes, improving performance. Its not like a 50% chance now, more like a 10% chance.I guess you need to use slick oil for this mechanism.. I thought since it was old the 'cleaning properties of 3in1 would help, but I guess if they did help, you need to flush it and replace it with slick oil. Could also be residues from the ultrasonic that were not cleaned out properly.Maybe it deoxidized the surface a bit (maybe I should give it a spray of deoxit) and made some kind of slurry/slime with the oxides and contaminants which made it worse uncleaned.I kind of wonder if you can dip a tiny little cup of alcohol into the ultrasonic and then a cup of silicone oil for superior penetration/cleaning of the mechanism.