Depth mike

There are two depth mics in my shop. One is a Shars set I bought new, and the other is old Craftsman maybe? Anyway, they have a domed or convex end on them so that the contact point is very small. Look at your other anvils/rods for the shape.

If you get the dome very close, then you could polish a couple tenths quite easily using your 123 blocks and a small inexpensive surface plate to check as you go. You might not make the metrology snob happy, but you should be able to get significantly closer to .000 than .001. With some, but not excessive, care you could get really darn close. If you have a tool and cutter grinder or surface grinder, and any kind of fixture for turning the rods you could turn a shallow cone pretty darn close and polish to finish with just tiniest of flats on the end. A cone is maybe not quite as durable as a dome, but you will probably wind up with a tiny flat or dome anyway.

I don't bother to "precision" calibrate the mic myself. I just take a quick reading on something close like a gage block, 123 bloc, etc, and then add/subtract the error to my final reading.

These are all flat on the tip . I can see the point of making the tip rounded or conical . These all have an adjustable collar with a lock ring on the top end , so I figured on polishing them a thou or three short then adjusting - start with the collars bottomed out (lightly) on the threads .

"Snag" wrote in message news:v5hnnl$29e1b$ snipped-for-privacy@dont-email.me...

I scored a Mitutoyo unit a while back at a yard sale . It only had one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing is they must be for a different model micrometer , they're all 5/8" too long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut them off to measure correctly in my unit . This will give me 0- 5" if I cut them to the appropriate lengths . It looks like I won't have to be absolutely on the mark since there is a calibration adjustment on each rod . I'm thinking that my Dremel in the toolpost clamp and a cutoff wheel , then a light polish with a fine grinding wheel also using the dremel . I have 123 blocks that I can set up to calibrate - maybe not as precise as a metrology lab , but I think close enough for what I do . Does this sound doable , and any suggestions ? Snag

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How about making a 5/8" long adapter sleeve for the head end, with appropriate threaded ends?

If you set the lathe compound 6 degrees off square each 0.001" division on the dial will move the bit 0.0001" sideways.

The mike will read the zero error and corrections will be to the one DIY sleeve, not all the rods. A screwup will cost you only the sleeve.

The biggest problem may be matching the threads. You need to match only the mike end, you can make the cap.

My depth mike is a Starrett so measuring its thread won't help you.

When I set my South Bend up for metric threading I found that the standard

Makes perfect sense to me. Not sure about them being flat though. I'll go double check both of my sets when I have another minute.

Makes perfect sense to me. Not sure about them being flat though. I'll go double check both of my sets when I have another minute. Bob La Londe

----------------------------------- The rods for my Starrett are flat across the end.

The way this is made there's nowhere to add a spacer sleeve . I've got a whole 40 bucks in this set of used rods o it's not a big deal if I screw one up . I think shortening the rods is really the only way to make this work . In case you aren't familiar with Mitutoyo depth mikes , the thimble is 2 pieces . The top half unscrews and the rod is dropped thru the hollow lower half . The top half is then screwed on to clamp and retain the rod . The top of the rod is threaded , the collar that is the clamping surface has 2 tiny setscrews plus a lock nut on top . There's enough threads that if I screw up and have to take a little more off I can , up to maybe .060" . About the only way I can see ruining one is to bend it . That's a tight hole it fits in .

I went and looked. I was in the back shop slitting some stock to width, and I was right there. The Craftsman set is flat. The Shars set is definitely radiused on every rod. I recall using the Shar's to get some dimensions for the rails on a handgun frame and I had to sweep it back and forth to make sure I was getting the dimension. With a square end I would not have had to do that.

I thought I had a benefit to the radiused end in my mind, but when I think through it doesn't seem to add up. Maybe just ease of grinding to length being just a theoretical single point instead of a perpendicular flat.

And this might not be as straightforward as I thought . Those collars at the top only want to rotate about 90° . Might be because the setscrews have flattened the threads but I haven't pulled a screw to see . Tomorrow will be soon enough .

On 6/26/2024 5:21 PM, Jim Wilkins wrote: ...

The way this is made there's nowhere to add a spacer sleeve . I've got a whole 40 bucks in this set of used rods o it's not a big deal if I screw one up . I think shortening the rods is really the only way to make this work . In case you aren't familiar with Mitutoyo depth mikes , the thimble is 2 pieces . The top half unscrews and the rod is dropped thru the hollow lower half . The top half is then screwed on to clamp and retain the rod . The top of the rod is threaded , the collar that is the clamping surface has 2 tiny setscrews plus a lock nut on top . There's enough threads that if I screw up and have to take a little more off I can , up to maybe .060" . About the only way I can see ruining one is to bend it . That's a tight hole it fits in .

I decided to look up calibrating the rods ... the collar doesn't rotate and the nut on top adjusts the length . The setscrews lock the collar in place . I'll be checking that in the morning .