Re: Depth mike

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

"Snag"  wrote in message news:v5hnnl$29e1b$1@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
 -----------------------------------
 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 100/127 gear set wouldn't give me the fine lens threads I wanted, 120/127 gave more. I used a spreadsheet to calculate and tabulate the inch - metric equivalence of several possible choices. Change gears were much cheaper in the early 90's. They weren't a direct fit, I had to make a bearing adapter.
 

   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 .
--
Snag
  It's great to be straight !