View Single Post
Old February 18, 1999, 08:33 AM   #4
bfoster
Senior Member
 
Join Date: October 13, 1998
Location: N. of Fords Switch, OK, USA
Posts: 297
Walt... In response to your query (by e mail) as to what a blade micrometer is: imagine the tip of a gunsmiths' screwdriver. Instead of a steady taper from the shank of the tool to the tip of the blade, these are usually "hollow ground:" viewed from the side, a short parallel section which fits (nicely) the slot of the screw is joined to the shank by two radii. In a blade micrometer, there are two opposed hollow ground "tips" between which the object is measured, the anvil being one, and the end of the spindle being the other. In this case the spindle doesn't rotate, movement back and forth only. The advantage in using one of these to measure case head expansion is that greater precision in measurement is obtained. Most rifle cases are tapered, as are most cases for "automatic" pistols- being able to repeat where you measure is much easier with a blade mike- if you can't repeat where you initially measured, you don't know what you are measuring. In practical terms, "readability" with blade mikes is approximately 5 times that of a good set of dial calipers. Any clear increase in case head size read on dial calipers would be cause to back off charge weight. Bob

------------------


[This message has been edited by bfoster (edited February 18, 1999).]

[This message has been edited by bfoster (edited February 18, 1999).]
bfoster is offline  
 
Page generated in 0.02287 seconds with 8 queries