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From: Snag <Snag_one@msn.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Depth mike
Date: Wed, 26 Jun 2024 16:52:23 -0500
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On 6/26/2024 3:21 PM, Bob La Londe wrote:
> On 6/26/2024 11:47 AM, Snag wrote:
>>    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 ?
> 
> 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
  It's great to be straight !