12-07-2012, 07:37 PM
To calibrate a depth micrometer start with the most-often used rod, the 0-1" one. Find a perfectly flat surface, such as a suface plate. I good quality parallel or other piece of flat ground stell will also work.
1. Wipe the surfaces of the plate, the end of the meauring rod and base of the micrometer all clean using a lint-free, oil and chemical free cloth or paper.
2. With the of secure in the micrometer's thimble, back off the micrometer to minus a few thousandths tenths of a millimeter.
3. Bring the thimble down to touch the plate, check the reading. If not zero, just make a note of how much the error is.
4. Using 1" (or 25mm if a metric micrometer) increments of gauge blocks under the micrometer, make the same check with each length rod. Note the error.
5. Compare error measurements. If all exactly the same, make the adjustment to the thimble body. If any one rod is good, make that your "zero" error rod and adjust all other rods using the little open-end wrenches until all read zero. Note that the "heads" of the rods will be very snug, and you may need to use a brass-jawed vise to hold it while you make an adjustment. The threads are relatively coarse pitch, so a TINY tweak of the adjustable head is all it takes to move it a few thousandsanths at a time.
That's about it!
HTH
Ken
1. Wipe the surfaces of the plate, the end of the meauring rod and base of the micrometer all clean using a lint-free, oil and chemical free cloth or paper.
2. With the of secure in the micrometer's thimble, back off the micrometer to minus a few thousandths tenths of a millimeter.
3. Bring the thimble down to touch the plate, check the reading. If not zero, just make a note of how much the error is.
4. Using 1" (or 25mm if a metric micrometer) increments of gauge blocks under the micrometer, make the same check with each length rod. Note the error.
5. Compare error measurements. If all exactly the same, make the adjustment to the thimble body. If any one rod is good, make that your "zero" error rod and adjust all other rods using the little open-end wrenches until all read zero. Note that the "heads" of the rods will be very snug, and you may need to use a brass-jawed vise to hold it while you make an adjustment. The threads are relatively coarse pitch, so a TINY tweak of the adjustable head is all it takes to move it a few thousandsanths at a time.
That's about it!
HTH
Ken