Neck turning - How much at once?

[1shot]

I'm working on a cartridge with a neck wall thickness of .015 . I need to take it down to .013. Would you do this in one pass or two? I'm using a Neilson "Pumpkin" with a Carbide mandrel, chucked in a lathe. Any advice and your reasoning behind it would be appreciated.
Thanks,
Lloyd

 

[searcher]

Everyone seems to have a technique that works best for them - mine has been to use two passes as I always end up ruining a case or two trying to take off that much in one pass. Some folks will do it on one pass with no problems. From my own experience, two passes takes about 70% longer than one.

 

[Preacher]

Cutting .001 a side in a single pass is really not a problem, to get to the .002 you need cut off..

 

[Erik Cortina]

One pass.

 

[Lapua40X]

Regardless of how much I need to remove I take it .001 at a pass. It takes a little longer but I'm not running on a production schedule and I want the cleaner finish that finer cuts provide.

 

[Erik Cortina]

Regardless of how much I need to remove I take it .001 at a pass. It takes a little longer but I'm not running on a production schedule and I want the cleaner finish that finer cuts provide.

.001 per side or on the diameter?

 

[Lapua40X]

Regardless of how much I need to remove I take it .001 at a pass. It takes a little longer but I'm not running on a production schedule and I want the cleaner finish that finer cuts provide.

.001 per side or on the diameter?

I zero the cutter on the surface, dial in .001 cut, and turn.

 

[artbosco]

I'm working on a cartridge with a neck wall thickness of .015 . I need to take it down to .013. Would you do this in one pass or two? I'm using a Neilson "Pumpkin" with a Carbide mandrel, chucked in a lathe. Any advice and your reasoning behind it would be appreciated.
Thanks,
Lloyd

For .002"? ... ONE pass. Ken Markel, the original owner of K&M Precision Shooting, once told me, as an experiment, he removed .015" in one pass without a problem.

 

[1shot]

.002 per side Eric.
Need to go from .015 to .013
.013x2=.026+.284+.310 on a .315 neck.
Lloyd

 

[Erik Cortina]

.002 per side Eric.
Need to go from .015 to .013
.013x2=.026+.284+.310 on a .315 neck.
Lloyd

Do it in one pass. Turn them about 500 RPM and back out real slow.

 

[jlow]

What I found is the smaller the cut, the more precise i.e. consistent. So for your cut, if you must, you can take a big cut first, say 0.0017", then come back and take that last 0.0003" off, you will get a smoother and more consistent finish in terms of thickness. The reason is a small cut will generate less heat and that is what you want.

 

[Erik Cortina]

What I found is the smaller the cut, the more precise i.e. consistent. So for your cut, if you must, you can take a big cut first, say 0.0017", then come back and take that last 0.0003" off, you will get a smoother and more consistent finish in terms of thickness. The reason is a small cut will generate less heat and that is what you want.

The heat is mostly generated by the friction between brass and mandrel. I take mine from .015" to .011" in one pass and hold +- .0002" tolerances in hundreds of cases.

 

[BoydAllen]

I would have no problem doing it with one pass. To avoid heat, make sure that your expander is a good match to your turning mandrel, use a good lube, and keep the RPMs low. I like to feed to the shoulder faster than will give a good finish, intentionally leaving material behind to be removed as I slowly feed back to the mouth. I don't go back. After the cut, I polish for a few seconds (2-3) with 0000.

 

[jlow]

What I found is the smaller the cut, the more precise i.e. consistent. So for your cut, if you must, you can take a big cut first, say 0.0017", then come back and take that last 0.0003" off, you will get a smoother and more consistent finish in terms of thickness. The reason is a small cut will generate less heat and that is what you want.

The heat is mostly generated by the friction between brass and mandrel. I take mine from .015" to .011" in one pass and hold +- .0002" tolerances in hundreds of cases.

The key word here is "mostly". The rest is generated by the cut. At least in my experience, the smaller the cut, the less problem, thus the suggestion.

 

[Erik Cortina]

What I found is the smaller the cut, the more precise i.e. consistent. So for your cut, if you must, you can take a big cut first, say 0.0017", then come back and take that last 0.0003" off, you will get a smoother and more consistent finish in terms of thickness. The reason is a small cut will generate less heat and that is what you want.

The heat is mostly generated by the friction between brass and mandrel. I take mine from .015" to .011" in one pass and hold +- .0002" tolerances in hundreds of cases.

The key word here is "mostly". The rest is generated by the cut. At least in my experience, the smaller the cut, the less problem, thus the suggestion.

.002" is a pretty small cut. A finishing cut on a lathe is usually .005" - .010" depending on material and cutting tool geometry, so .002" on brass is a very fine cut.

I guess he can take it down to .013" in one pass and if not satisfied he can shave another .0002" which will not make much difference in chamber clearance.

 

[jlow]

What I found is the smaller the cut, the more precise i.e. consistent. So for your cut, if you must, you can take a big cut first, say 0.0017", then come back and take that last 0.0003" off, you will get a smoother and more consistent finish in terms of thickness. The reason is a small cut will generate less heat and that is what you want.

The heat is mostly generated by the friction between brass and mandrel. I take mine from .015" to .011" in one pass and hold +- .0002" tolerances in hundreds of cases.

The key word here is "mostly". The rest is generated by the cut. At least in my experience, the smaller the cut, the less problem, thus the suggestion.

.002" is a pretty small cut. A finishing cut on a lathe is usually .005" - .010" depending on material and cutting tool geometry, so .002" on brass is a very fine cut.

I guess he can take it down to .013" in one pass and if not satisfied he can shave another .0002" which will not make much difference in chamber clearance.

I think what I suggested was 0.0003" but a slightly larger number would be OK, just in two parts, big and small.

 

[jlow]

I am basically following this suggestion by German here:

http://riflemansjournal.blogspot.com/2009/12/reloading-neck-turning.html

This is the paragraph that covers the point in question:

"If you have decided on a cut that will reduce thickness by 0.0015" or more, you should make two passes on the brass. Limit the first pass to a 0.0015" reduction and finish the operation on the second pass. Obviously you won't be resetting the cutter twice for each case, so do them all at the first setting, readjust and then do the second pass on all of them. If you have to cut that much to get the brass to clean up, you might consider better brass. If you're cutting it to fit a particular chamber or to maintain a uniform thickness across several types of brass (as I do) then that's just the breaks of the game. A second cutter might be a useful idea; that's another nice thing about the K&M, it's price is low enough that having a few isn't a tremendous burden as it might be with some of the pricier models out there."

 

[SS427]

Has anyone tested one pass versus 2 or more passes for on target accuracy? I can't imagine it making a difference with so little brass being removed in this case.

For my 6PPC I go from virgin brass to .00825 (or so) in two passes. The cases look great and I too finish them off with steel wool. On both passes I go fairly quickly into the shoulder and then very slowly back out for a smooth ridge free neck. That seems to be the key.

 

[ridgeway]

I take one pass, no problems. I turn BR down to .009" to fireform for a Dasher. So that is taking roughly .003" in a pass. I get a nice smooth finish and make no finish passes. Pulling the turner back slow takes care of any spring back or flex in tool. Then again, I make sure my cutter is nice and sharp on my K&M turner. If its not cutting like cutting butter, it needs touched up. It usually lasts for awhile before needing touched up. I touch up on a diamond wheel on my carbide tool bit grinder.

If you have a difficult time taking .003" off brass, your cutting bit needs attention.

 

[M14AMU]

http://riflemansjournal.blogspot.com/2010/07/reloading-should-i-turn-necks.html