neck thicknesses

[Brathany]

It's not the precision. Your trying to measure a curved surface with a flat object. The ball mic is made to measure tubing and round objects.

When I get .0135-14 with calipers, that gives me an OD of loaded bullet .312. Measured by caliper and Mitutoyo micrometer. Like clockwork. So, my relative measurement of the case neck thickness with calipers translates to a direct measurement of the OD.

If for some reason the case neck thickness was required to fly to Mars, the Aerospace industry wouldn't like my way, but alas, handloading ammunition is never needed to be to a degree as Aerospace. I can't think of one instance a .0005 tolerance is needed to be hit exactly in handloading.

 

[ntsqd]

What cajun said. It's what I said above, too. Calipers are completely inappropriate for performing this measurement due to the geometry of the measuring faces of the caliper.

Yeah, we probably all do it now and again, but if you need an error-free measurement calipers are the wrong tool. When you're setting up the dims for a custom chamber you want an error-free measurement.

 

[Brathany]

What cajun said. It's what I said above, too. Calipers are completely inappropriate for performing this measurement due to the geometry of the measuring faces of the caliper.

Yeah, we probably all do it now and again, but if you need an error-free measurement calipers are the wrong tool. When you're setting up the dims for a custom chamber you want an error-free measurement.

They work just fine for this operation.

 

[ntsqd]

If you're happy with the built-in error I know that I'll never change your mind.

 

[Brathany]

If you're happy with the built-in error I know that I'll never change your mind.

It's not an error if it works and works consistently for a desired result.

 

[ntsqd]

It is still a known error.
It's not consistent, that's part of the problem with doing it that way. Each different ID is going to yield a subtly different measurement. The whole problem isn't just this small error, it is that eventually you have a stack of them and you don't know how far astray they've led you until something doesn't work like it was expected to. Ask any Engineer, Designer, or Draftsman about "Large assembly tolerance stack analysis" if you want to give them nightmares.

Up to the person doing the work to decide if that error is acceptable or not. When I might be laying out a custom reamer it would not be. Not even close. If I'm looking at a new lot of brass and deciding whether or not to run them thru the neck turner, then that error isn't too important because the turner will correct it. But when I set up the turning tool it is hugely important so that I get the expected neck thickness.

 

[Brathany]

It is still a known error.
It's not consistent, that's part of the problem with doing it that way. Each different ID is going to yield a subtly different measurement. The whole problem isn't just this small error, it is that eventually you have a stack of them and you don't know how far astray they've led you until something doesn't work like it was expected to. Ask any Engineer, Designer, or Draftsman about "Large assembly tolerance stack analysis" if you want to give them nightmares.

Up to the person doing the work to decide if that error is acceptable or not. When I might be laying out a custom reamer it would not be. Not even close. If I'm looking at a new lot of brass and deciding whether or not to run them thru the neck turner, then that error isn't too important because the turner will correct it. But when I set up the turning tool it is hugely important so that I get the expected neck thickness.

There would only be an error if my loaded neck diameter was above my target .312-.3125". When my caliper reads a case neck thickness of .0135-.014" I know that will give my loaded dia. at the neck .312" with a positive tolerance of .0005" or .3125" consistently for each round I make. I have hundreds loaded up right now with that target diameter. So, you can't say my process isn't consistent because every single round made tells me I am. When they don't read .0135-.014 then that OD diameter shows me. It really is that easy.

 

[Lionel Boyd Johnson]

If I understand your question correctly, you need a tool like one of these:

Neck Turner Builder | Neck Turning Tools | Precision

Neck Turner Builder | Neck Turning Tools | Precision Micro Adjustable Neck Turner Tool & Best Neck Turning Tools for Accuracy

kmshooting.com

Perhaps my question was not clear. I have the K&M neck turning tools and have used them successfully for many years. What is not clear is how one sets up the cutter depth to taper from .0135"-.014" over the length of the case neck. Thanks again, Ed

 

[Brathany]

Perhaps my question was not clear. I have the K&M neck turning tools and have used them successfully for many years. What is not clear is how one sets up the cutter depth to taper from .0135"-.014" over the length of the case neck. Thanks again, Ed

You can't cut a taper on the K&M tool. Chambers are tapered a bit in the neck area from base to mouth. You turn a consistent thickness with the tool.