Depth Mic adjustment

Eric M · May 27, 2014

Does anyone happen to know the thread pitch on the adjusting nuts for Starrett and Mitutoyo depth mics? I have a couple that need adjusting, and it would be nice to have an idea of how much to "nudge" the adjusting wrench to bring them back into line. I know Starrett is notorious for using "oddball" threads (or should that be "proprietary" threads) for their stuff; not sure about Mitutoyo.
Plowing through their websites has not been productive...
Thanks in advance!

daveallen · May 27, 2014

Turn it 1 full turn and check how much it changed, the difference will = the pitch

Gordon B. Clarke · May 27, 2014

daveallen said:
Turn it 1 full turn and check how much it changed, the difference will = the pitch

I probably should mention this as it's probably similar with inch micrometer as with metric ones. One full turn on a mechanical metric micrometer is usually .5mm and the ones with the "thicker" thimble 1mm.

https://www.google.dk/search?q=micr...mD4gTV9YC4AQ&ved=0CAYQ_AUoAQ&biw=1366&bih=650

I know they aren't depth micrometers

but the principle is exactly the same.

Eric M · May 27, 2014

daveallen said:
Turn it 1 full turn and check how much it changed, the difference will = the pitch

Thanks, dave. I already knew how to figure it out; I was hoping somebody may know the actual thread pitch already.

manualmachinist · May 27, 2014

You might try calling and asking Starret.

Then post what ever you find out for everyone else too.

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Gordon B. Clarke · May 27, 2014

Eric M said:
Thanks, dave. I already knew how to figure it out; I was hoping somebody may know the actual thread pitch already.

You've got me really puzzled with your post. You knew how to figure it out yet wanted to know the pitch?

if one revolution moves the spindle 1/10" inch then the pitch is 10 TPI. 2/10" is 5 TPI and so on ad infinitum

All mechanical ones I've seen in metric have either a pitch of 0.5mm or 1mm.

TGTool · May 27, 2014

Actually I don't begrudge the OP asking the question since it's a matter of curiosity. However, the answer, whatever that might be, still leads to just a hypothetical solution. Suppose I KNOW that my mic has 40 threads and thus .025" per revolution. Now I want to correct an error of say .0017". Can I turn the nut 1/15 revolution (approximate)? Not me. It's still a tweak and check, tweak and check proposition so knowing the gnat's ass pitch still hasn't gotten me very far.

The real Leigh · May 27, 2014

TGTool said:
Suppose I KNOW that my mic has 40 threads and thus .025" per revolution. Now I want to correct an error of say .0017".
Can I turn the nut 1/15 revolution (approximate)?

The question cannot be answered in the general case, because there are two possible sources of error:
1) the thread pitch is wrong (don't know how that could happen, but suppose...), or
2) the error is the result of localized wear, which would require considerable investigation to quantize.

Obviously error #1 would be a manufacturing defect that would likely appear on many examples of the tool, and be cause for rejection.

Error #2 just means the tool is worn out and should be replaced.
This can happen with a tool that makes a single measurement on a production part day in and day out, for example a large outside mic.

You cannot fudge a measurement in any case.

- Leigh

manualmachinist · May 27, 2014

Would it be possible to chuck the rod in a collet chuck and set up a .0001" indicator on the face of the nut while making the adjustment? Seems this method would get you really close I one move.

wesg · May 28, 2014

Depth micrometer. Has the interchangeable rods in it to measure 0-1, 1-2, etc. At the top of the rod is a nut that's adjustable to 'zero' each rod. He wants to know the pitch of that thread, to estimate how much to turn it.

This has nothing to do with the pitch of the screw in the mic' itself.

Now, if all you own is a Tesa, which are not adjustable as far as I can tell, I can understand the confusion.

I like MM's idea.

Gordon B. Clarke · May 28, 2014

TGTool said:
Actually I don't begrudge the OP asking the question since it's a matter of curiosity. However, the answer, whatever that might be, still leads to just a hypothetical solution. Suppose I KNOW that my mic has 40 threads and thus .025" per revolution. Now I want to correct an error of say .0017". Can I turn the nut 1/15 revolution (approximate)? Not me. It's still a tweak and check, tweak and check proposition so knowing the gnat's ass pitch still hasn't gotten me very far.

Let's forget hypothetical and move into the real world. How would you turn a nut (any nut) exactly 1/15th of a revolution without measuring movement backwards or forwards? I'll even "let" you forget about backlash

Eric M · May 28, 2014

TGTool said:
Actually I don't begrudge the OP asking the question since it's a matter of curiosity. However, the answer, whatever that might be, still leads to just a hypothetical solution. Suppose I KNOW that my mic has 40 threads and thus .025" per revolution. Now I want to correct an error of say .0017". Can I turn the nut 1/15 revolution (approximate)? Not me. It's still a tweak and check, tweak and check proposition so knowing the gnat's ass pitch still hasn't gotten me very far.

It also let's me know if I can have regular coffee, or if I must use decaf before attempting any "tweaks"...
All seriousness aside, I did find out (by looking in the right area of their website) that Starrett uses #5-40 threads on their depth rod adjusting nuts. After emailing Mitutoyo Tech Support, here is the response I got from them (verbatim):
We have no info about it, just that we sell the rods with the nuts installed.

We can ask Japan if it’s important.

Eric M · May 28, 2014

Gordon B. Clarke said:
You've got me really puzzled with your post. You knew how to figure it out yet wanted to know the pitch?

if one revolution moves the spindle 1/10" inch then the pitch is 10 TPI. 2/10" is 5 TPI and so on ad infinitum

All mechanical ones I've seen in metric have either a pitch of 0.5mm or 1mm.

Yes, Gordon, I could have. However, rather than "reinvent the wheel" (so to speak) and make the measurements, I thought perhaps someone here may already have this information readily available, and save myself some time...

TGTool · May 28, 2014

Gordon B. Clarke said:
Let's forget hypothetical and move into the real world. How would you turn a nut (any nut) exactly 1/15th of a revolution without measuring movement backwards or forwards? I'll even "let" you forget about backlash

Q: What do you call a dog with no legs?

A: Don't matter what you call him. He ain't gonna come.

Gordon, my point exactly. Since it's impossible for all practical purposes to turn the nut exactly the rotational amount required, it's immaterial what the thread is. It comes down to "adjust until it's right." Same thing zeroing the barrel. You don't really care how many fractional degrees to turn it, you just have to get the marks to line up. Only in this case you don't get handy little marks to work with.

Eric M · May 30, 2014

manualmachinist said:
You might try calling and asking Starret.
Then post what ever you find out for everyone else too.

Contact Us

Since you asked, here's what I found out:
Starrett depth rod adjusting nut: #5-40 threads
Mitutoyo depth rod adjusting nut: M4 x 0.5 threads

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