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View Full Version : help reading a Lyman Vernier Reloaders Micrometer?


cpileri
March 1, 2002, 04:49 AM
I am holding a Lyman Vernier (the manual one, not digital or electronic) Reloader's Micrometer, and have it set exactly correctly upon a .458 Barnes Solid slug.
For the life of me, it measures .457.
IS that right?
or am i reading it incorrectly?
The directions are not too clear on the package insert. Can anyone help me to read the thing????
Its easy to get to .45 (i.e the hundredths of an inch place, the .00 point), but the thousandth and ten-thousandths of an inch (the .000 and .0000 place, the "8" in .458) i am confused on as the numbers are sideways and no big arrow points clearly to a "read here" line.
Thanks for your help.
Carl

Jim Watson
March 1, 2002, 01:00 PM
Awright,
You have the micrometer rotating sleeve turned out just past the .45 graduation on the fixed barrel, right? And the 7 on the rotating sleeve lines up - more or less - with the main index mark under the numbers on the barrel, right. Ok, so far you are reading .457" in thousandths. Those "sideways" numbers on the barrel and their long markings are the vernier scale for ten-thousandths. There are 11 marks numbered 0 - 9 and another 0, for 10 divisions, right? OK, if the 7 on the sleeve is not lined up just perfectly with the index mark, say you are really between 7 and 8 for thousandths, you will see that one of those "sideways" numbered marks will line up with a mark on the rotating sleeve. Any mark, it doesn't matter which, what counts is which "sideways" number it is. That is the ten-thousandths measure. So if the "sideways" 2 mark lines up, the reading is .4572" If the 7 IS aligned perfectly with the main index, you will see that both the start and end zeroes on the "sideways" vernier scale line up with marks on the sleeve. So that would be a reading of .4570"

I hope that is clear enough for you and Monsieur Vernier (Pierre Vernier, the real person who invented the scale in the 17th century.) to get along. The key is that ten divisions on the "sideways" vernier scale cover the same distance as nine divisions on the main sleeve scale. So they kind of jump into alignment from one to another with 1/10 th the movement of one main scale division.

I am not surprised that one of those solid bronze bullets was a bit undersized in order to reduce pressures from what is required to drive a jacketed bullet through the rifling. So you are very likely getting a correct reading of .457" or so. Unlike check weights for scales, I don't know of any ready, economical source for gauge blocks. You could get a machinist to measure that bullet for you and keep it as a reference.

labgrade
March 19, 2002, 10:24 AM
Good enough description, Jim, on "how to."

One thing too, for a good read with a micrometer, is to have the anvils (contact/measuring points) clean. Gently close the anvils against a piece of clean, plain paper using the ratchet/friction device on the thimble until firm contact is made. Slide the paper out & recheck for zero.

Always use that ractchet/friction thimble-thing for consistant anvil pressure.

Too, a check set can be had rather inexpensively (about $20) from a machinist/tool outlet (Shop Tools, etc.). Get Grade B (as opposed to AA - labgrade ;) which are more expensive & not really needed for what you're doing) rectangular gage blocks from DoAll (or similar) in increments of .1250, .5000, .6250 & 1.0000 (assuming a 1" mic.) This'll check your mic's threads at 1/4 icrements (not 1/4 of the travel, but of the threads' form, which does the actual measuring) ...