Neck turning issues

[bobcat93]

I have a Sinclair neck Turner, new lapua 6mm. BR brass.
1) I have full length sized all my brass
2) I have trimmed all brass to 1.555"
3) I have chanford and dibured all brass
4) when I turn cases I just can't kiss the neck with out getting uneven cuts on the shoulder..
How to fix and still cut down fare enough so I don't get a donut

 

[Preacher]

Damn, that don't look good....
I'm not familiar with the Sinclair tool so may not be much help.
I use a K&M and do not have problems, you shouldn't either, Sinclair is good stuff usually..
#1--- you need to expand the cases before you try to cut the necks......... No need to FL size them...
#2--- the expander needs to be 100% compatible with the cutter your using..
#3--- If your cutting that far into the neck your not set up right, you need to stop cutting just barely into the shoulder, and the cutter should have a stop built into it that you control.
#4---About the only time you'll get donuts from neck turning is if your necking down and pushing a lot of brass into places it wasn't meant to be in..
If you want to talk, send me your phone number in a PM....

 

[dkhunt14]

Did you run the brass through an expander mandrel to match your turner? It also looks like your advancing the turner too quickly. I like to use power and turn around 100 RPM in a drill. I also don't take much off with a pass. I prefer to do it in 2 or 3 passes. With the last one only taking about .005 at most. Go to youtube and watch some videos. Matt

 

[BoydAllen]

From the interior finish of your neck, it looks like you may have a lubrication issue. Also, do you expand your necks before turning them? If you do that, do you lube the inside of your necks before you do that, lube the turning mandrel before the first case, and then add a drop of lube before you do the next case? The reason that you have the cut down the shoulder is that your cutter matches the shoulder angle of your cases, and your case neck is slightly cocked in relation to the case body. This can be caused in the expanding if you do not have the right or enough lube, and run the case over the mandrel too rapidly. Using a cutter with a greater bevel angle than the cases will eliminate cutting to the outside of the shoulder, but as long as there is some neck cocking the cut will be a little uneven. As long as it is not too bad, that will straighten out on the first firing. Back when I used Sinclair turning equipment, I found that the turning mandrel was a bit large, and with the material that it was made of (steel, not carbide) that brass tended to build on it right under the cutter, causing necks to be thinner after that happened. (I carefully reduced the diameter of the turning mandrel and polished it a bit.) For that reason I developed the habit of checking each neck after it was turned, with a neck mic. that measures to .0001. Are you turning by hand or with power? I prefer low RPM power. I feed to the shoulder fast (feed rate not RPM), and then come off very slowly, one time, and then polish the outside with 0000 under power for a second or two. Looking at the cut, it may be that the point where your cutter bevel starts is a bit to sharp. Carefully modifying the cutter so that it has a little radius there will make it cut a broader swath and smooth out your finish.

 

[fguffey]

Donuts, again I have cases that will never form a donuts; I form cases that have donuts before I ever fire them. Then there are donuts that form because of the way the chamber is designed.

Then there are donuts that form because of bad habits.

F. Guffey

 

[bobcat93]

Yes I use an expanding mandrel I will try to cut less and see how that works thank you for the reply

 

[bobcat93]

From the interior finish of your neck, it looks like you may have a lubrication issue. Also, do you expand your necks before turning them? If you do that, do you lube the inside of your necks before you do that, lube the turning mandrel before the first case, and then add a drop of lube before you do the next case? The reason that you have the cut down the shoulder is that your cutter matches the shoulder angle of your cases, and your case neck is slightly cocked in relation to the case body. This can be caused in the expanding if you do not have the right or enough lube, and run the case over the mandrel too rapidly. Using a cutter with a greater bevel angle than the cases will eliminate cutting to the outside of the shoulder, but as long as there is some neck cocking the cut will be a little uneven. As long as it is not too bad, that will straighten out on the first firing. Back when I used Sinclair turning equipment, I found that the turning mandrel was a bit large, and with the material that it was made of (steel, not carbide) that brass tended to build on it right under the cutter, causing necks to be thinner after that happened. (I carefully reduced the diameter of the turning mandrel and polished it a bit.) For that reason I developed the habit of checking each neck after it was turned, with a neck mic. that measures to .0001. Are you turning by hand or with power? I prefer low RPM power. I feed to the shoulder fast (feed rate not RPM), and then come off very slowly, one time, and then polish the outside with 0000 under power for a second or two. Looking at the cut, it may be that the point where your cutter bevel starts is a bit to sharp. Carefully modifying the cutter so that it has a little radius there will make it cut a broader swath and smooth out your finish.

 

[bobcat93]

Boyd Allen thank you so much

 

[BoydAllen]

Let me correct myself. (first cup of coffee) Looking again at the picture, your cut does not go down the shoulder all the way, and on the side where it extends the most, there is a little step at the outside of the cut, so your cutter bevel angle is less than your shoulder angle. if it was more than the shoulder angle, it would feather out to nothing at the outside. Sorry about that. My bad.

 

[Brians356]

The reason that you have the cut down the shoulder is that your cutter matches the shoulder angle of your cases, and your case neck is slightly cocked in relation to the case body.

This points up a downside of nearly matching cutter angle to shoulder angle - any slight asymmetry or tilt is magnified visually by the lopsided swath on the shoulder. The case shown here looks very bad, but IMO it really isn't. The difference in thickness of the shoulder wall between the "scalped" portion and the untouched portion is probably too small to be measured accurately, and therefore insignificant.

Back when I used Sinclair turning equipment, I found that the turning mandrel was a bit large, and with the material that it was made of (steel, not carbide) that brass tended to build on it right under the cutter, causing necks to be thinner after that happened. (I carefully reduced the diameter of the turning mandrel and polished it a bit.)

Boyd, what do you consider the ideal gap between the turner mandrel OD and the case neck ID? (Note that my Sinclair turning mandrels, in both 22 and 6mm, measure .0013" smaller than the corresponding expanding mandrels. I would think that with spring-back that would leave ~.001" play, but I'm not sure.)

 

[Brians356]

Boyd,

Also, what lube do you use for a) expanding and b) turning?

 

[Dusty Stevens]

I think you have lube issues. Expanding lube problems most likely. I use stp and marvel mystery oil mix.

 

[Dusty Stevens]

Donuts, again I have cases that will never form a donuts; I form cases that have donuts before I ever fire them. Then there are donuts that form because of the way the chamber is designed.

Then there are donuts that form because of bad habits.

F. Guffey

Tell us about your methods. Seems you have it figured out but youre hi-hatting us here

 

[ireload2]

Do you ever post details of your wisdom?

Donuts, again I have cases that will never form a donuts; I form cases that have donuts before I ever fire them. Then there are donuts that form because of the way the chamber is designed.

Then there are donuts that form because of bad habits.

F. Guffey

 

[BoydAllen]

A couple of tips:
I like carbide turning mandrels. For expanding, there are a number of variables. The spring back of the brass is one. Another is the time that the full diameter of the expander is in the neck, and the number of times that the neck is expanded. The other is the time between expanding and turning. If you expand one day and turn another, the fit will become tighter. I prefer neck being able to slip over the turning mandrel without undue force, but that they not be able to be felt to rock, once on the full diameter section. If you have a carbide turning mandrel, a good lube (several work fine), and are sufficiently slow RPM, your heat related problems should be minimal. One way to do this is to use an old, less expensive turner, that has a steel mandrel that you have reduced in diameter to the point that the fit is too loose for a final cut, to make your rough cut, leaving .001 to clean up. With the loose fit, there will be no heat problem (properly lubed) and once the material is removed (assuming that you are taking a significant amount off) the tension on your carbide finish mandrel should be reduced. If you want to experiment with different expander mandrel diameters, you may find it useful to measure how much your turning mandrel is expanding your necks. I would do this using a pre set and drag through method with a .0001 micrometer, so as not to oval the empty neck when taking your before measurement. I believe that K&M will do custom mandrel work. My absolute favorite mandrel for expanding untouched .220 Russian brass up to 6mm is a carbide model that PMA makes for use with their die body, that has a very long taper. With strict attention to press technique, the results are excellent in terms of expansion induced case runout. (necks being cocked relative to case bodies)

 

[bobcat93]

Well I didn't lube the expanding mandrel. I just ran the case through and put a bit of redding case lube on the cutting mandrel. Also I think the 6 mm. BR is a 30° shoulder and I have a 30° cutter install.. I can change cutters so it won't hit the shoulder..
On another note I was worried about my cases coming out of my press with major run out after seeing the cut on the shoulder..I hope that isn't the case ..I have a redding T7 press and have never had a problem with it before.. But I don't have a tool to check case run out. .
Also the only reason I was turning my case by hand is because I forgot to order a power shell holder from Sinclair.. ( I did order one this a.m...lol)..

 

[bobcat93]

Ok..so I used a different cutter and lube.
I lubed the inside of the case mouth and ( slowly) expanded the neck, then turned neck..looks good to me
One more question
If you can tell by the pic, should I cut more onto the shoulder. I'm left with a little ledge/ or ring ..at the neck shoulder juncture..or is that normal

 

[rocketron]

in the first post you stated you fl sized cases. did you have the expander ball installed? if so check the dia of the ball vs the mandrel. the neck id may be to big.

 

[dkhunt14]

That looks a lot better. I wouldn't go no deeper on the shoulder. After you get your case holder so you can run in a drill. Take steel wool and run it on the neck to help smooth out the little lines. On your first picture it looks like the neck was crooked. That or the fit to the mandrel was real bad. Matt

 

[Dusty Stevens]

Like matt said you got it now