Re: Depth mike

On 6/26/2024 2:52 PM, Snag wrote:

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 ?

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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.
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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.
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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.
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    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 .

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.
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Bob La Londe
CNC Molds N Stuff
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