Originally Posted by SidecarFlip
Being a toolmaker by trade and business, I disagree with your statement (using the upper jaw for measurement). It's not proper or accepted, but then I wonder how many people really know the proper use of a micrometer......
Jaw calipers were designed primarily to remove the 'human factor' when measuring. No need to develop the proper 'feel' for thimble tension.
I'm curious as to why a micrometer should be used however.... Please elaborate....
Most professionals can get fairly close with a good caliper but one of the first things they teach in machinist school (or used to anyway) is not to use a caliper for anything less than .005 tolerance. There is too much spring in even a good caliper and the tendency is to "help" it out a little, I watch people that should know better wiggle a caliper every day to "help it seat". If you give a micrometer to 3 different people who know how to use it you will likely get 3 different readings on a standard, a gauge block for instance, but they will be within a tenth (.0001) or 2 of each other. Give the same three people a caliper and the readings could vary by a thousandth or 2. A micrometer is simply more accurate and in a tight chamber .0002 can make a difference, I always use a micrometer to check case head expansion, they are simply more accurate. As for using the upper jaw, grab a gauge pin and try it tomorrow, as a tool maker I'll bet you'll be surprised just how close you can get. Sorry if I came off a little abrasive in the previous post, it was not my intention.