WTB/Info on a good ball micrometer

[1shot]

I'm tired of the time consuming task of measuring both the I.D. and O.D. of brass and loaded ammo. That said, I'm looking to buy a good ball micrometer that is capable of measuring to 4th (.0001) decimal point out, or information on what is the tool to buy that meets the above criteria. digital would be a nice extra, but not a necessary. If someone has an extra that they aren't using please contact via PM or e-mail.
Thanks in advance for any help,
Lloyd

 

[mikecr]

http://www.sinclairintl.com/reloading-equipment/measuring-tools/micrometers/sinclair-digital-case-neck-micrometer-prod38161.aspx

 

[BoydAllen]

This modified ball mic will let you get into places that conventional ones will not, and it will not be as subject to bridging across surface irregularities.
http://www.kmshooting.com/catalog/miscellaneous-items/mitutoyo-wall-thickness-micrometer_60-degree-modification.html
With the addition of a stand to act as a third hand, you should be all set.
http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=micrometer%20stand&sprefix=micrometer+st%2Caps&rh=i%3Aaps%2Ck%3Amicrometer%20stand

 

[OldManTA]

Boyd's recommendations are spot on for what you have described. Realistically, outside a controlled environment like an instrument lab the fourth place number won't mean much. If the micrometer spindle has a ratchet and is used in a repeatable manner you will get pretty close to the same clamping pressure on the work piece making the third decimal value more credible. If you use a bushing die and/or don't measure at the same point in from the mouth at each point around the circumference of the neck you will also likely get variations in thickness particularly close to the shoulder/neck junction.
If you are trying to get away from the tedium of measuring neck wall thickness with a tubing MIC you can use one of the gages where you rotate the case around a sized insert with a dial indicator riding on the OD of the neck. HOWEVER, that will not be as precise and if the fit of the insert is not quite snug then you will get wobble equal to the clearance. With that method you can measure case wall thickness approaching three decimal places and ascertain thickness variations. you must preload the dial indicator about .020 so there is constant pressure on the work piece and the lash is taken up inside the indicator gear train.
I hope that is helpful and it was not my intent to be patronizing.
Tom Alves

 

[BoydAllen]

One little trick that I figured out when using a friend's Sinclair neck thickness gauge with a mechanical dial indicator, was to use extension of the stem above the indicator to apply force with my thumb, taking multiple readings around the neck by stopping every few degrees and applying a little thumb pressure.

 

[mikecr]

Contact force is one reason dial indicators don't work as well as mics. The second reason is common lack of ball anvil. Third reason plagues all, lack of stop for datum control.

Ideally, for speed and accuracy, we'd have a really good digital indicator with:
-increased contact force
-turned down spindle face
-ball anvil
-datum stop
But nobody offers this.

You can use a less interfering area of the spindle face through adjustable anvil contact(sneak right into a donut):

 

[PMA3]

1 SHOT

I have the K&M modified version Boyd Allen mentioned. It's new and never been used....sell for $125.

Paul