Quite minor variations in the gauging force can also produce errors of a tenth or more; there is good reason to be skeptical of any measurement to a tenth precision taken without using the friction thimble or ratchet speeder. All this, plus the previously mentioned effects of even modest temperature changes, hints at the need for being very conservative and cautious when dealing with precision of 0.0001 inch and finer .
Good quality micrometers also have some provision for an adjustment to eliminate backlash resulting from wear in the screw thread and mating nut. Again, the technique differs from brand to brand and is described in the printed material that came with the tool. In truth, it takes a very long time indeed for detectable wear to develop.
After use, always clean off the exterior of a micrometer before storing it way, but do not use compressed air for this, as dirt may get forced into the concealed threads. If a micrometer feels sticky or notchy in action, do not continue to use itâ€”there may be something trapped in the threads, and further use will only damage them. The tool will have to be dismantled, a job perhaps best left to experts. Finally, do not store a micrometer with the spindle screwed down onto the anvil; for some reason that I, at least, do not understand, this seems to encourage corrosion of the contact faces.