How to calibrate this inside mic

[sundown57]

Just bought an older Starret inside mic set but it's off like 3 tho. the set came with a spanner wrench but for life of me i cant figure out where it goes, Does any one know how to calibrate this type mic ?

 

[jbobb1]

I never direct read an ID mic. I transfer with an OD mic. That being said, you typically calibrate each rod you use.

 

[sundown57]

it seems strange to grab it with pliers and twist it. and even odder is it comes with a spanner wrench

 

[benmychree]

The spanner may be to adjust the nut inside the mike; the one I have takes a small open end wrench to adjust the tip end of the rods, and I agree that it is best to use an outside mike to read the inside mike.

 

[MrWhoopee]

I just went out and looked at my SPI. The spanner engages in the screw holes, allowing you to rotate the barrel while holding the thimble.

 

[benmychree]

I just went out and looked at my SPI. The spanner engages in the screw holes, allowing you to rotate the barrel while holding the thimble.

Starrett does not work like that.

 

[Alcap]

I’m curious, did you check all the different sizes to if there all reading .003 off ?

 

[sundown57]

I’m curious, did you check all the different sizes to if there all reading .003 off ?

no, I hadn't. I was concentrating on the 2 I needed now. but that was a great call. I went ahead and checked them all and your right. some are off more than others. so it has to be that you unscrew the rod tip to calibrate it. Going to try that this morning. still wish I know what the wrench was for lol.

 

[sundown57]

for everyone following this, Benmychree was right, I did not have a wrench small enough but i did put the tip of the rod in a vise and pliers on the knurl and it turned. So I was able to calibrate all the rods. what an odd design. thanks for all the help again guys.

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