In my post about vernier calipers, I highlighted one rugged option for making highly accurate measurements. When building projects that involve things like sliding fits, interference fits, shafts and bearings, rotating parts, measuring sheet metal thickness (and the list goes on, and on), accurate and repeatable measurements in the range of 1/1000 of an inch become very important. In this Tool School, I look at another option: the micrometer. A standard micrometer is capable of the same 1/1000-inch accuracy as the vernier calipers, and micrometers that incorporate a vernier scale are capable of measurements an order of magnitude more accurate: 1/10,000 of an inch. In addition, the variety of forms micrometers take allow measurement of a far larger variety of things than would be possible with calipers. Here's how to use one.