Neck Turning....

L

lcw

Guest
just looking for the preferred set-up for using a lathe to turn case necks. Tried to chuck my K&M tool in head stock and put shell holder in compound, was getting a lot of erratic results in finish. Please help. Thanks.

Linc
 
When I use my 7x14 lathe to turn case necks I chuck the K&M shellholder in the headstock, and hold the turner body in my hand. There's some wobble of the turner body that varies from case to case leading me to believe that it's due to straightness or squareness of the case - even with Lapua's. From this I could see how there could be some wierd and varying results if both the shellholder and turner body were held solidly.

I probably don't understand all (or even most of) the possibilities since I'm not a machinist, but that's what I found.
 
adamsgt said:
method is the one I'm going to try to use on my 7 X 10 lathe.

http://www.6mmbr.com/powerneckturn.html
Click to expand...

A suggested modification to Mikes mandrel design. I make the mandrel to look generally like the one in the photo on 6mmbr.com except, I make the mandrel with 3 different diameter steps instead of just the 0.243" diameter.

On the right end I have a fit that is about 0.238" diameter by about 3/16" long. This is to rest the case neck on when starting to press it on the mandrel.

The next step is exactly bullet diameter (normally 0.2433"). I make this fit 1/16" longer than the case neck length. This accomplishes two things. First, most of the dreaded donut forms from necking the case shoulder up to 6mm from 22 cal. By pressing the case neck over this longer fit, the excess of the donut is pressed outside. Secondly, by making the step exactly bullet diameter, you can mike the finished case neck for the exact desired finish diameter.

The third step, I turn to finish case neck diameter minus about 0.0005" by about 3/16" long. This makes a place to "park" the turning tool while changing cases. By turning this fit half a thousand under and keeping it blacked with a magic marker, if the turning tool happened to move in, it would make a mark thus saving a case neck from being turned undersized.

One other suggestion. I set a 0.0001" resolution dial indicator against the back of the actual cutting tool. This is the only way, except trial and error, you can feed the tool to get an exact diameter because trying to move the turning tool in or out using the cross feed dial with its 0.001" graduations (or even a DRO) is not really possible to get a neck diameter as close as needed for benchrest.
 
Use a Drill Press and Lee shelholder

I get very consistant results with my 16 speed drill press..I use the shell holder and Lock Stud from a Lee case length gage and put that into the Jacobs chuck in my drill press..I run the drill press at about 100-150 rpm..
I using my old trusty Sinclair 1000 neck turning tool hand held, lubricate the mandrel with a quality bolt lug lube, then feed slowly to get a smooth cut in one pass... attention paid on the slow back-out pass to get a very smooth finish....
I can measure no variation with my tubing mike, when using deliberate and slow feed in and out...
I hold and feed the neck turning tool by hand...
If your mandrel is a tight fit in the case neck you can use pleirs to tighten the shell holder to the lock stud and your case will not spin in the shell holder..
This method is about as fast as any I have tried, and set up time is minimal..
 
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