Incorrect Neck Bushing Sizes

[dblinden]

If this has been discussed previously, I couldn't find it.

Thought I'd check the inside diameter of my Redding coated bushings and found that they were 2-3 thousandths smaller than the nominal size. Decided to purchase two of the plain steel bushings hoping to get one that measures at .266, for example. The .266 and the .267 I just received each measure 2 thousandths smaller (.264 and .265).

Any thoughts or recommendations?

Thanks - Dennis L

 

[fdshuster]

dennis L: How are you measuring them? I'm referring to the inside diameter.

 

[dblinden]

I would like to say I had access to an electron beam microscope, but it was checked out at the lab and hasn't been returned. So I just used inside blade calipers.

Dennis L

 

[jonbearman]

If you are using calipers all bets are off. You need gage pins period or a zeiss measuring system.

 

[fdshuster]

Dennis L: You are losing a lot of the true measurement because of the flats on the blades of the calipers. That's why your I.D. measurements are always smaller than they actually are. If you had parrallel perfectly sharp edges, (sharp like a razor blade) on the caliper blades the dimensions would be extremely close to actual.

I also do not have any special type of measuring tool, I just take an O.D. measurement of the sized case neck with a high quality micrometer. Perfectly fine for our level of measuring accuracy requirements, and shows the actual end result of each bushing size.

I then keep notes of the actual sizing diameters that each bushing produces. Ex: .269" bushing sizes .2695". Or .289" bushing sizes .2885".