I need to slug a couple of barrels and I'm looking at doing at least one chamber cast. I need to figure out what the &@$%@@(#!! I'm doing when it comes to crimping, so it would be nice to be able to measure the thickness of a case at the neck.

I remember just enough from an earlier conversation here to know that I'd probably like a Mitutoyo, and I'm lazy enough to prefer a digital readout.

What would you recommend?

I have a few different types, but the basic Mitutoyo 0-1 Inch digital micrometer gets used second to my 8" Mitutoyo digital calipers. I've never had them go out of calibration (stored and handled properly). The non digital ones don't get handled out of my laziness but do save money over the electronic.
Starrett is pretty popular as well but I've not used their digital stuff.

You might consider interchangeable anvils ($$), if you are going to measure something like case wall thickness to very accurate measurements. I don't know how you'd measure the case thickness with a standard micrometer. The cartridge size would be limited by the faces of the "mic" and and then you'd have to trig it out to account for the chord length that you are actually measuring. With a pin on the end of a interchangeable micrometer, you'd just have to select a small enough pin.

quote:

Originally posted by Il Cattivo:
I need to slug a couple of barrels and I'm looking at doing at least one chamber cast. I need to figure out what the &@$%@@(#!! I'm doing when it comes to crimping, so it would be nice to be able to measure the thickness of a case at the neck.

What would you recommend?

Are you measuring the case thickness or OD? Completely different animals (and tools required).

I guess both. I'm working off of an article by Brian Pearce in Handloader from a few issues back.

So I guess I'm looking at a ball micrometer and a "plain old" micrometer?

Something like this Mitutoyo would come in handy for measuring a lot of things.
You should be able to get within .001" with a little practice.

https://www.msi-viking.com/Mit...lute_Digital_Caliper

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Mitutoyo

I have both Starrett and Mitutoyo in quite a few different configurations. I prefer the Mitutoyo digital ones.

 
Purchase a 1/2" gauge block to calibrate your 0-1" micrometers/calipers. I have an old Lufkin 0-1" micrometer I got years ago somewhere (yard sale? who knows). It is dead on the gauge block. I prefer Mitutoyo Digimatic calipers and micrometers, and have several in different work areas. And, for some odd and unknown reason, I purchased a Mitutoyo 293-348-30 Digimatic micrometer which reads out to .00005". It is impractical for any reloading or other home use. You never get the same reading twice at the stated accuracy range, but it is certainly always accurate to .0001". I hardly ever use it for practical measuring.
 
 

Sounds like Mitutoyo built in a margin at the .0000X" level to be sure of getting it right at the .000X" level.

The rule of thumb used by machinists is that your measuring device should have a resolution of at least 10 times the tolerance you actually require for the measurement.

In other words, if you have a part that is supposed to be be within 0.001" of 2.000", meaning it can be between 1.999" and 2.001", the tolerance is 0.002" and the rule of thumb says you want to use a measuring device with a resolution of at least 0.0002".

https://www.mahr.com/en/Servic...ID=110464&Overview=0

Some of it comes down to questionable repeatability at the limit of the precision of the instrument, but mainly, it's this:

If you measure the above part as 2.001" using a device that measures to 0.001", how do you know the part isn't actually 2.0015", which is out of spec?