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[How do I?] Depth mic calibration

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B

Brento

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#1
I posted yesterday how to calibrate the rods for my 0-3 starret depth mics. I foind the wrench and adjusted the screw and now on both 1-2 and 2-3 rods i am off a thou when i measure in a middle number on the spindle. For example 1.588 ill get 1.589. And then as i get lower on the spindle it will go back to about a half thou out. I am dead on when i measure the nominal 1” in the 1-2 and 2” in the 2-3. Does anyone have any ideas to get this to read within a half a thou? Id like to get it as close as i can even if im doong hobby work right now.
 

woodchucker

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#2
what are you using to check against?
I assume you verified that?
Depth Mics are tough. First question, do you have a ratcheting thimble? Mine is not, so its real touchy. You have to hold it tight and feel when it touches. It is unusual to be out in the middle but not at both extremes.
 
B

Brento

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#3
Well first i use various gage blocks on a granite stone that is calibrated at work. Yes my mic does have a ratchet thimble but im more of a feely type of guy. I have ratchet even on my regular mics but i dont use them. If i use them i do it to get close and then feel it after
 

BtoVin83

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#4
If I remember correctly that is a used mic. it's possible the error is caused by thread wear and they read correct on the ends as that is rarely used. Send them back to the factory and have them rebuilt maybe? I think they also have a threaded collar on the thimble to take up wear on the spindle, might check that.
 
B

Brento

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#5
ill see what starret can do for me. The only issue is that the 0-1 adjustments were just about dead on.
 

EmilioG

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#6
Starrett charges around $153 to tune up a depth mic. Try MR Tool Repair. You may have to wait a while to get it back though.
Starrett mechanical DM's are only good to .001" Anything better and your in Mitutoyo digital territory. To calibrate, you really need good gage blocks and a flat reference surface. Starrett will sell you all the parts. Their website has a parts breakdown. It uses Internet Explorer.
 
B

Brento

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#7
Well i do have the flat regerence surface and gage block. I was just hoping there was a way to get these fixed without spending much on them.
 

EmilioG

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#8
Best are the gage blocks with the hole in the center. Mitutoyo makes them but a few of these blocks start to get expensive. You can get close with accurate 1 2 3 blocks, but even those are usually a bit oversize by .001" Contact MR TOOL, he can probably repair and calibrate for you for under $50
 
B

Brento

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#9
Is he on this forum?
 
B

Brento

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#10
I can deal with under 50 i bought the set for 15 so i cant complain when the set is usally like 300 but i still wanna keep the cost down.
 
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