Expander vs turning mandrels

[Caduceus]

I've got several of Jerry Stiller's excellent neck turning tools. Over the weekend, I tried using the latest addition, the 30cal turner for the first time on some 30BR cases I'm making up.

Jerry recommends use of Sinclair expanders prior to turning on his tool and I agree that with the 6 and 6.5 cal tools, these are perfectly compatible, giving cases which are a snug fit on his turning mandrels.

However, the 30cal cases are too darn tight on the turner - no fault of that device, I need a bigger expander. When I mic the mandrels, I come up with the following:

Turning Mandrel,Stiller) - .30620"
Expander Mandrel,Sinclair) - .30685"

I would have thought the .00065" difference would be enough but not so. Possibly, the brass springs back to a smaller diameter when taken off the expander since if you run it up the press again, it seems to want to get re-expanded but I've never had this happen with other cases which are still in their original calibres. Maybe they somehow know they were originally 6mm necks and they don't want to accept reality?????

Anyway, so now I either need a slightly larger expander mandrel,which, why and how) or I need to get the turning mandrel made a bit smaller,same questions apply). I'd rather not mess with the turning mandrel because of the way it is set up on an eccentric axis.

Ideas?

PS. Yes I am lubing the mandrel and inside of the case necks - lube ain't the answer to this one.

 

[Forum Boss]

If you haven't tried imperial die wax as a lube, give that a shot. It is a little thicker than liquid lubes. Otherwise, call Sinclair. I bet they can get you an expander mandrel that's .001 bigger than your turning mandrel. The K&M 30cal mandrel should be slightly bigger than Sinclair's, but I don't know if it will work in the Sinclair expander body.

 

[dreever]

Before you do anything you could try the Pumpkin mix of 50/50 Mobil 1 and STP. Slicker than whale snot and just as hard to clean up!

If that doesn't work here's a solution. Get the next bigger size turning mandrelfrom Sinclair take it to a machine shop and have them turn it to ALMOST the size you want. Then finish it by polishing it down by hand in an electric drill with Flitz and some 0000 steel wool.
I did this because I went with a Ron Hoehn 6MM carbide turning mandrel in my Sinclair tool so I needed a bigger expander mandrel, which Sinclair couldn't provide. Cost me an extra seven bucks, but now it's exactly what I want.

As for lube, I prefer FP-10

 

[Gollum]

Why not polish the turning mandrel down a bit?

 

[Stonewall]

Greg -could you give us the diameters of the other mandrels you used in 6mm etc and brass sized. I will be getting this neckturner soon.I just bought a very small lathe to take care of these items such as expanders -now I just have to learn to use it.
Glenn

 

[BoydAllen]

I have several turners. My K&M setup works well with the following mandrel dimensions: Expander-.2433, Turner-.2422,carbide)Another lube alternative is RCBS Case Lube II, which is water soluble.

 

[Stonewall]

Another good lube for turning necks is SC FP-10.Thanks Boydallen for the information.
Glenn

 

[outlawsix]

Have ordered a Stiller neck turner in 6mm. For those that have one. What is the O.D. of the mandrel? Also what is the O.D. of a K&M expander mandrel?
Thanks in advance.

 

[outlawsix]

Exactly what I was looking for. Thank you.

 

[Aussie_bob]

In my 30cal the turning mandrel is .002 smaller than the expander which lets them turn freely and has no effect on the neck turning procedure as you set your cutter off the mandrel for wall thickness on your necks. In my case it is a two or three stage exercise anyway as i am expanding 6BR cases to 30BR and need to turn off the donut before turning the rest of the neck and i like to clean up then trim to length before the final turning that way i can set up the turner to turn all the cases to the same point on the shoulder.