08-03-2013, 07:21 PM
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.
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.