a vernier will tell ya everything a ball mic will.
P
Never seen a ball mike that was vernier.
Using a caliper of any type will not produce accurate
thickness measurements on a curved surface.
How wide is that flat on the jaw?
You could try to calculate the error based on the radius
of the curve and the width of the contact area.
The face of the caliper is not zero thickness.
When you are concerned with 1/10,000 variations around a small
cylinder like a case mouth ball and rod anvil are required.
with measuring rounds loaded with bullets in them, one, if they have a pumpkin turner, only needs to get close. Even if one does cases on a lathe, one is pretty much only concerned with what the o.d. of the case with a bullet in it. That's what I think anyway. With 600 finished cases, I don't turn many now a day.
I just now went in to my gun room and measured a finished case with both a Ball Mic and my Lyman vernier, they both said .009". Not even close you say? Very close I'd say.
Pete
Last edited by Pete Wass; 09-25-2019 at 01:04 PM.
For comparison I measured a neck with my Mitutoyo ball mic at .010. I then picked up my new Mitutoyo Digimatic calipers. I found if I really bared down on them it would measure .0105. I have found over the years that you could get the measurement that you want by cranking down on the thimble a little harder if necessary.
Always take two or three readings with your eyes closed. Whether using Ball micrometer, caliper or standard micrometer.
Chet
Bottom line, when measuring to .0001's(tenths), calipers are simply the wrong tool for the job, period.
Not trying to be argumentative here BUT..... seriously?
I have the tools mentioned plus Time Prec, K&M, Sinclair et al... and they have pros and cons but I can get ALL of them to cut outsides to tolerances I can't easily detect. Like I have to be careful how I hold/handle the cases...... but TENTHS in thickness using anvils and balls?
Exactly how are y'all's smoothing the insides? How exactly are you removing the hideous wrinkly CRUST on the inside of new brass? I've got inside reamers, ie "chucking reamers" in tenths sizes..... I've got LE Wilson (odd # flutes) and Forster (even # flutes) and PTG (staggered flutes) and even some spiral fluted ones as well as the K&M end-cut-only setups.
I've single-pointed the insides on the lathe......
After mandrelling, "blowing out" with pistol powder, 'spander balling, hydro-forming.....
And IMO this whole thing is freakin' SILLYGet yer runout down into the "fractions of tenths"..... then open clearances up to 3 thou cuz, "Thin To Win"....
For WHAT? "guiding means?" . . . . "consistent release?" . . . . "consistent seating pressure?"
But hey.... that's just me. Once I figgered out how to easily and repeatably get my ES down into single digits I kinda' moved on to other items.
Life Is Short
LOL
al
edited to add..... My Jackson is of course a copy. Because I'm a youngster, and a hack. Never knew the man![]()
It is rather easy yo adjust most neck turning tools in 'tenths.'
And an error of even one thousandth on a neck that is 0.0100 thick is getting up there.
I shoot with a 'clearance' of only 0.0020 on the diameter of my chamber.
So 0.0010 all around.
And each has been cast and measured to a tenth.