Neck turning, getting an understanding

[J P Brown]

Hi everyone. I'm just starting to neck turn.
I will be doing 22br to remove the thickness after necking down and tidy up the neck variances. And 223 because I can and to get some practice in.
I have the k&m carbide cutter Turner.
Iv read a few articles and they mention cutting into the neck slightly to help not get donuts, as the thick shoulder brass flows into the neck. This makes sense.
My cases are looking more like the one with the pink background, the single case.
So, things iv read lead me to believe they should look more like the other picture.

So does it matter, will both cases be OK and not eventually get a donut?

What is the easiest way to monitor wether or not I have a donut?

If I have a donut, I understand it will be there on the inside after firing, will it move to the outside after full length sizing with an expander ball?

Thanks for any help.

 

[Alex Wheeler]

Your bullets should not be seated deep enough to get into that doughnut area. If they are I'd throat the barrel. The doughnut is only an issue if it contacts the bullet. Tun into the shoulder just a few thousandths other waise you may leaves some necks in your chamber. I prefer hss cutters, you dont need or want carbide with brass. The relief angle on the cutters usually isnt right and makes the cutter to agressive and it will want to dig in. A mild relief, a slight radius on the leading cutting edge and I like to just touch the edge with a fine stone to take off that super sharp edge. If the cutter has a little tendency to push the brass toward the mandrel you will get necks that you can't even measure a .0001" variation in...

 

[rardoin]

Although the picture on the left does not have the magnification I need to see the neck/shoulder junction clearly it does appear that you need to cut a little further toward the shoulder. However, the case in the right hand picture appears to be turned with a cutter profiled to the shoulder angle; you cannot expect the K&M cutter to produce a cut with that appearance. Look at your turned case with a magnifying lens and adjust the turning mandrel depth to just start to cut into the radius at the N/S area. If you cut much deeper with the K&M tool it will cause a thin area at the beginning of the shoulder.

 

[Preacher]

The left one is not enough, and the right one is to much. Some where in the middle of those 2 is good....

 

[Shaggy357]

I have an old school Forster trimmer/neck turner. I set my brass so the pilot goes into the brass beyond the neck/shoulder joint. I use an expander ball the same diameter as the pilot so the brass slides onto the pilot with no wiggle room and is supported full length of the neck. I cut entire length of of the neck, but do not go into or past the joint with shoulder. My brass looks like your photo on the left. If there was a donut at that junction, my turning method would remove the donut material in the neck so if I happened to have to seat a bullet that deep, I should not have a thick spot in the neck. I try really hard not to seat bullets that deep. As stated before, you would have to have a cutter profiled to shoulder angle to get a cut like in your second photo. I dont shoot anything requiring that kind of tolerance.

Good luck,

Steve

 

[PMA3]

The left one is not enough, and the right one is to much. Some where in the middle of those 2 is good....

Ken Markle, the original owner of K&M, long ago told me to cut about .025"-.030" into the shoulder to prevent any donuts. I took a bight colored Post It, cut a few strips, measured with a caliper, then cut down until I had two strips...one @ .020" and one @ .030". These strips helped me visualize what those dimensions looked like....I still keep those strips for reference. Since then, I acquired a used lab microscope to better inspect the cases before and after neck turning. After turning over 1000 cases, you sort of get the hang of it and know what you're looking at.

 

[J P Brown]

Looking at the first picture, I think I have been going a little further as well. I can usually see a ring where the cutter has just gone into the shoulder I suppose it is.
With my 223 after a couple of firings iv noticed a ring on the outside, then again a clean ring on the inside after sizing as the expander ball has passed through.
Is this normal? It's almost like the cases need turning again. I can't feel the ring on the outside or the inside with a paper clip.
The last picture is one of my own cases, it's a better example of how far into the shoulder iv been going.

Thanks for all the help.

 

[J P Brown]

OK. So I see the left isn't enough the right is too much or at least requires a cutter with the right cutting angle.
I try to stop when I can barely feel a step that the cutter has left in the shoulder.
So... Is the standard cutter I have acceptable for the job?
Is it just a matter of judging the cut depth with the cutter I have?

Thank you.