Neck turning - How much at once?

[BoydAllen]

Due to my work writing about equipment, over the years I have accumulated a number of different turners, five to be exact. Some cutters work better than others. I think that this is the reason for the differing opinions on this subject. They all produce usable necks, but some work better than others. The last brass that I cut was with PMA's best tool. Carbide everything (optional) expander, turning mandrel, and a standard carbide cutter. It works really well, and the adjustment mechanism is unique and works extremely well. IMO there are a lot of fellows who make problems for themselves turning necks because they insist on a fit on the turning mandrel that is tighter than it needs to be, turn at too high of a speed, and go back and forth on the neck. My necks typically are +-.0005.

 

[GPat]

Taking .002" in one pass is really not an issue. When I'm asked, I like to let guys decide on their own from their own personal experience, if they have no experience with neck turning I tell them what I do myself.

I make two passes on my PPC brass, the first taking it to .010" - .0105" the second taking it down to .0082" or .0088" depending on the neck of the chamber. As a general rule I don't like to take off much less than .001" unless for one reason or another I have to. I prefer to see a nice curl of the material coming off the brass rather than a fuzz. .0003" to me is a fuzz.

My suggestion is to try turning the full .002" off a piece or two, then try turning .001" then the second .001". See if it makes a difference to YOU. I doubt it will, but make that judgement yourself. I can pretty much guarantee it won't make a difference on target.

Pat

 

[CatShooter]

If you use a good tool, I don't think it is that critical.

I had to cut 1,100 Lapua 6mmBR cases from 0.0145" to 0.009"... I made one cut, slowly from the mouth to the shoulder and back. I used a Forster with a 1/4" power drill (1,440 rpm). I used heavy oil, and moved the cutter slowly in and out, and did it in one cut - I got the same tolerances as Boyd did.

 

[Joe R]

I use a Gracey neck shaver and it spins at 1,480 rpm, much faster than most hand cutters. I've taken .0015-.002 in one pass at the time, the only problem I had was that the Imperial sizing wax wasn't working causing some occasional binding. Since I've switched to petroleum jelly I haven't had one stick on me.

 

[Cassidy]

What is a good tolerance for necks. I saw a video on YouTube (Jack Neary) some months ago (6PPC); he said that a neck thickness of 0.0082 (good) makes a big difference from 0.0086 (not so good). This information told me (since I am new to neck turning) that I need to have a close tolerance in my necks; I've been able to get +- 0.0002 or so with my 6.5x47 lapua cases using a K&M turner with carbide pilot, but would like to get +- 0.0001 if this is feasible (it may not be with any turned). I use a ball mic (0.0001) and check 3-4 points around the neck to be sure these neck thicknesses are all the same. I found that even a slightly loose fit of the case neck on the neck turning pilot causes the neck to very slightly wobble when turning, and this results in an unacceptably large tolerance from point to point around the neck. So if I have to, I FL size the cases using an undersized neck die (a smaller diameter than the neck turner pilot), then use the mandrel to push the neck diameter back out to where it fits the case neck very snuggly (I know this probably works the neck too much). Then I turn. I havn't got ball-mic data yet to see if one turn or two turns (one large pass, followed by a small pass on the neck) is more precise at the 3-4 points round the neck (but I bought two K&M turners just for this purpose). What's a good tolerance for neck turning.

 

[BoydAllen]

Two suggestions:
Get a different tool to drive your cases. PMA and 21st Century make good ones. I have all three. Your cases won't wobble as much. Also, technique plays a big role in what results you get. Don't fight the wobble. Let it happen on both ends, drill and tool. Also, always keep the cutter cutting so that it keeps the neck pinned to the mandrel, and do not go back once you are off the first time. This is why I go to the shoulder with fast feed, and off with slow. Leaving metal to be removed on the trip back to the mouth keeps the neck hard on the mandrel all the way in and out. If you trim or chamfer before measuring necks, you stand a pretty good chance on reading a slight ridge that has been thrown up by either operation, if you place your mic. so that it is on that area.

 

[GPat]

What we aim for is 0.0000, but a total variation from thickest to thinnest of .0003" (+/-.00015") is usually OK. I usually get a variation of +0 / -.0001. But +/- .00025" (total of .0005") would probably make me look at my setup. We've got to remember that when we're measuring to the ten-thousandth of an inch a lot of things come into play, not the least of them is the user. We also should remember that .0001" = 1/10,000, that's tiny and hard to measure repeatedly if you're not a machinist (hell it's hard for a lot of machinists).


Jack goes with the "thin to win" strategy on neck turning and shoots a .262nk. I tend to listen to him and have used .0082 for my .262nk, but use a .0088 turn for my .263nk. A lot of the "thin to win" strategy is to be on the safe side for variations in the chamber (maybe the reamer isn't a true .262 for example) and variations in measuring tools and the ability of the user to read the tool that closely. I can take three guys that are familiar with measuring equipment, hand them a part, tell them to measure a certain dimension to the ten thousandth and possibly come away with three different measurements.

1400+ rpm??? What's your rush? I've used my Dewalt Power screwdriver with variable speed and I've had it running fast while neck turning, but nowhere near that. I guess if it works for you, go for it.

Bottom line is this: Turn a few pieces, mic the neck wall and adjust the thickness until you get what you're after. Clean them up and seat a couple of dummy rounds. Mic the neck on the dummy rounds, checking the specific diameter as well as the variation. If you have the clearance you're looking for go for it.

 

[1shot]

All of you are giving really solid, valid advice on why you do it a certain way. My lathe has a 4 jaw chuck that I can get the mandrel to completely zero out by adjusting the jaws individually and using a good magnetic base dial indicator. I turn the chuck at 540 rpm and get a very smooth finish. The set up is the time consuming part, but with a "Pumpkin" for each caliber, it really cuts down on the time. BTW, I use a old product called Tapmatic as my lube. Everything stays cool on the carbide mandrels ans clean-up is a breeze. Please keep up the tips, this is a good thread.
Lloyd

 

[Dos XX]

All of you are giving really solid, valid advice on why you do it a certain way. My lathe has a 4 jaw chuck that I can get the mandrel to completely zero out by adjusting the jaws individually and using a good magnetic base dial indicator. I turn the chuck at 540 rpm and get a very smooth finish. The set up is the time consuming part, but with a "Pumpkin" for each caliber, it really cuts down on the time. BTW, I use a old product called Tapmatic as my lube. Everything stays cool on the carbide mandrels ans clean-up is a breeze. Please keep up the tips, this is a good thread.
Lloyy

Do you mean Tap Magic for lube? Haven't seen that in a while.

 

[Erik Cortina]

I use Liquid Wrench white lithium grease for expanding and turning my necks.
I spray grease in a shallow container such as a coke bottle cap. I dip my necks in it which gets grease on the inside and outside of necks. I expand necks and grease stays put which comes in useful when turning. The grease on the outside allow for less friction between chips and cutter blade, which yields a better finish on the cut.
http://www.amazon.com/Liquid-Wrench-L616-Lithium-Grease/dp/B00200EFJA

 

[dixieppc]

All of you are giving really solid, valid advice on why you do it a certain way. My lathe has a 4 jaw chuck that I can get the mandrel to completely zero out by adjusting the jaws individually and using a good magnetic base dial indicator. I turn the chuck at 540 rpm and get a very smooth finish. The set up is the time consuming part, but with a "Pumpkin" for each caliber, it really cuts down on the time. BTW, I use a old product called Tapmatic as my lube. Everything stays cool on the carbide mandrels ans clean-up is a breeze. Please keep up the tips, this is a good thread.
Lloyy

Do you mean Tap Magic for lube? Haven't seen that in a while.

I've been thinking of trying something new for turning lube so I looked up Tap Magic. There are a lot of varieties of the same stuff including:
Industrial Pro Tap Magic
EP-Xtra Tap Magic
EP-X3 Tap Magic
Xtra-Thick Tap Magic

Which one would you suggest to use for neck turning on a Carbide Mandrel?

Regards....

 

[Joe R]

Which one would you suggest to use for neck turning on a Carbide Mandrel?

I don't have one but I thought the whole point of getting a carbide mandrel is so that you don't have to use lube. What am I missing?

Joe

 

[CatShooter]

Which one would you suggest to use for neck turning on a Carbide Mandrel?

I don't have one but I thought the whole point of getting a carbide mandrel is so that you don't have to use lube. What am I missing?

Joe

No noooo... it is so the thing won't wear out - I wore a flat spot on a steel mandrel - the carbide mandrel won't wear - but there is tremendous friction between the case neck and the mandrel, especially under the cutter.

 

[4Bowhunter]

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

one pass is all you need as Erik has said. no madder how much you need to take off. backing out is the key.

 

[liljoe]

If you have a pumpkin turner and the cutter is getting tired and dull, order a replacement from Pat at PMA Tool. He has a carbide replacement cutter that is really nice.
Joe

 

[mr45man]

.0003 with a hand held tool , thats impressive.

 

[Willie]

one pass is all you need as Erik has said. no madder how much you need to take off. backing out is the key.

It's been 3 years, he's got it figured out by now.