Starrett 103-C Adjustment

[chucketn]

I inherited A Starrett 103-C 0-1” micrometer from my late father. It came to me without a case, instructions, or calibration wrench. Does anyone out there have one of these mics that could provide the instructions as to the calibration? I have a gage block set coming in a few days, and will be able to check its accuracy, but would like to be able to adjust it if necessary.
Chuck

[PixMan]

I'd have to see a photo of the micrometer because it's older than all my Starrett catalogs. Also, do you have the means to measure the diameter of the barrel body? The barrel is usually adjustable in two ways. One, very small adjustments are done by rotating the barrel within the frame. This affords only .001" or so movements because the index line would look odd if it weren't straight across. You would know it's adjustable that way if you see a tiny hole in the barrel, usually 180º from the index line and near the frame. I have a good number of those little "pin spanner" micrometer wrenches, I could send you one that fits.

The other way of making major adjustments is that the thimble of the tool is rotated. They are usually on a short taper lock, and accessed by removing a screw or the ratchet speeder (of so equipped) from the end of the thimble. It can be tricky to knock the taper loose without damaging the barrel or thimble, especially if the micrometer hasn't been disturbed for many years.

[chucketn]

Pixman, I'll take a picture of my mic tomorrow. Thank you for your kind offer.

Chuck

[chucketn]

My mistake, the mic is a Starrett #203-C, not #103-C.

The dia of the barrel is .476” and the pin hole is a snug fit for a #52 drill shank. The Starrett measures the drill shank at .0625”
Pics here: http://s571.photobucket.com/user/chucket...03-C%20mic

Chuck

[Mayhem]

I think PixMan has one of those exact mics but I could be mistaken...

[PixMan]

I have a No.T230RL, though my dad's toolbox may have one of those in it. I haven't had time to go through his box, but when I do I'll probably have some duplicate tools to sell off.

In the meantime, I'm heading back over to the shop later tonight and will check for a wrench. It's hard to tell from the photos just how far out of calibration that one is, but it does appear to be bad enough that you'll have to remove the screw in the end and dislodge the thimble to rotate it back into position. You should only use the wrench on the barrel for very small movements, usually only .001" or less in adjustment.

[PixMan]

These photos show what I mean by having the index line at the center of the barrel as the micrometer lays flat.

It's hard to tell for certain in your pictures, but it does appear to be rotated up a bit.

[chucketn]

PixMan, I apologize for the poor quality of my pictures, I was never good with a camera and mine is quite old.
I have found or been referred to several descriptions of mic calibration and cleaning. I cleaned the mic with paper between the jaws, closed the mic and the zero does line up. The barrel is smooth, so it does not need adjusting there. I expect to receive my gage block set today and will check the mic on several blocks.
I just wanted to be able to adjust it if necessary.

Chuck

[PixMan]

No need to apologize on pictures. I worked as a pro photographer for a few years, and have lots of experience with everything from studio lighting to large format (4x5) photography. These days, I'm lazy with it too and just grab my little Canon Elph SD800is for most quick shots, or my Droid Razr Maxx phone if the camera isn't close by.

[chucketn]

I received the gage block set a few minutes ago. I am very pleased to report that both Dad's Starrett 203-C and the flea market JT Slocomb 2-3" mics check 100% with the gage blocks!
Thanks to TomG for the video showing how to use the gage block set and everyone that had info to share on the care and adjustment of Mics.
PixMan, did you find a Starrett or Slocomb pin spanner I can talk you out of?

Chuck