case neck won't fit on turning arbor

[Chaotik]

I have a 21st Century neck turner and use a 21st century titanium neck turn arbor (.242) and 21st centrury expander mandrel (.243). I am unable to fit the case neck after FL sizing and expanding onto the neck turning arbor. I have used imperial die wax, HBN, and neolube#2 as lubricants, but the brass will not go onto the arbor. New 6mmBR Lapua brass so no donuts.

What am I doing wrong?

 

[mike mccormick]

I would say your best bet would be a smaller arbor, or sand/ polish yours until it fits. Either that, or use a bushing die with a bushing that gives you the desired result

 

[jepp2]

What am I doing wrong?

Nothing based on what you share. But how are you measuring your arbor and mandrel? If you say caliper, realize the potential measurement error can be larger than the clearance. Generally, I find when using 21'st Century arbors and mandrels, the fit is on the loose side, never tight.

Try getting a good measurement using a mic that reads to 0.0001" to really see what your diameters are.

 

[B Nettesheim]

Sounds like you need a .244 mandrel

 

[STRSRLVR]

I have a 21st Century neck turner and use a 21st century titanium neck turn arbor (.242) and 21st centrury expander mandrel (.243). I am unable to fit the case neck after FL sizing and expanding onto the neck turning arbor. I have used imperial die wax, HBN, and neolube#2 as lubricants, but the brass will not go onto the arbor. New 6mmBR Lapua brass so no donuts.

What am I doing wrong

I have a 21st Century neck turner and use a 21st century titanium neck turn arbor (.242) and 21st centrury expander mandrel (.243). I am unable to fit the case neck after FL sizing and expanding onto the neck turning arbor. I have used imperial die wax, HBN, and neolube#2 as lubricants, but the brass will not go onto the arbor. New 6mmBR Lapua brass so no donuts.

What am I doing wrong?

All the brass I turned on my 21st lathe fit snug. Did you anneal your brass before resizing? Maybe you have too much spring back. You could order a couple different sizes or set of expanding mandrels from 21st that go in .0005 increments to adjust neck tension. That’s probably the simplest. You don’t want them too loose cause the cut won’t be as nice. Royal case & die lube works really nice for turning although it’s a little messy.

 

[Rset]

Did you possibly reverse the mandrels?

 

[Chaotik]

I measured using a micrometer, and repeated it several times to verify. The brass was annealed before sizing. The 21st century mandrels are labeled with either an E for expander or T for turning, so they were not reversed.

 

[Nick Caprinolo]

I would think that it is obvious that you need a larger expander mandrel. Measure you expander and the inside of the case neck. I bet they are the same. You need a larger size.

 

[Chaotik]

I would think that it is obvious that you need a larger expander mandrel. Measure you expander and the inside of the case neck. I bet they are the same. You need a larger size.

Unfortunately, I think you may be right. When I bought this several years ago from 21st Century, they offered only a 6mm expander mandrel and only 6mm turning mandrel, and there were no options for ordering a specific diameter. I guess I was hoping that they would be compatible.

 

[Nick Caprinolo]

Unfortunately, I think you may be right. When I bought this several years ago from 21st Century, they offered only a 6mm expander mandrel and only 6mm turning mandrel, and there were no options for ordering a specific diameter. I guess I was hoping that they would be compatible.

That's sad. Why not call them and see if they can help you. Or take it to a machine shop and have one made to what you need. I wonder if the expander die will accept other brands of mandrels. Most of this stuff is interchangeable.

 

[Chaotik]

That's sad. Why not call them and see if they can help you. Or take it to a machine shop and have one made to what you need. I wonder if the expander die will accept other brands of mandrels. Most of this stuff is interchangeable.

I will call them tomorrow, but lately they have only been communicating via email. Used to be able to call them and John would answer or call you back and help with the problem.

 

[Dusty Stevens]

@Petros284

let me yodel to my man.

 

[Webster]

I have a 21st Century neck turner and use a 21st century titanium neck turn arbor (.242) and 21st centrury expander mandrel (.243). I am unable to fit the case neck after FL sizing and expanding onto the neck turning arbor. I have used imperial die wax, HBN, and neolube#2 as lubricants, but the brass will not go onto the arbor. New 6mmBR Lapua brass so no donuts.

What am I doing wrong?

Could be springback. I doubt a .243 mandrel expands to .243. It should expand to .243 then springback to a slightly smaller diameter. It may have worked better if if you just ran the expander in without FL sizing. Did you chamfer the neck I.D and O.D. Annealing a couple cases with a torch would tell if it's springback. Don't remember if I turned before or after FL it's been two years. I use the mandrel that came with my K&M turner don't know what the diameter is. I don't think you can gall a neck i.d. if the mandrel is well lubricated. I use oil and re-oil frequently.

K&M you tube video on proper turning.

 

[jepp2]

Just checked my "stash".

I have 1 E24, and 4 T24's. Here is my measurements on them:
E24 0.2423"
T24 0.2410"
T24 0.2409"
T24 0.2411"
T24 0.2406"
So you can see the clearance mine provide vs yours.

 

[mikecr]

You should not have sized necks.

 

[Nick Caprinolo]

Sizing the necks seems to be a sensely endeavor as you are making them smaller and then expanding them. I can't see any advantage in this.

 

[Petros284]

@Petros284

let me yodel to my man.

Thanks for the shout out Dusty! Standard expander mandrel sizing is .2422 (+/- .0002") in the 6mm. I have sent him a .2430" incremental to try out to see if it helps.

 

[fkimble@charter.net]

You no not need to full length size your new brass. Simply run your expander mandrel thru them to make necks round and proper size. FL dies over size the necks. Did you take out the FL die sizer button? This will make it even worse.

Frank

 

[Dusty Stevens]

Thanks for the shout out Dusty! Standard expander mandrel sizing is .2422 (+/- .0002") in the 6mm. I have sent him a .2430" incremental to try out to see if it helps.

Thanks pete. We appreciate your help always.

 

[Chaotik]

You no not need to full length size your new brass. Simply run your expander mandrel thru them to make necks round and proper size. FL dies over size the necks. Did you take out the FL die sizer button? This will make it even worse.

Frank

Yes, the sizer button was removed.

Thanks for the shout out Dusty! Standard expander mandrel sizing is .2422 (+/- .0002") in the 6mm. I have sent him a .2430" incremental to try out to see if it helps.

Pete is sending me a .2430 expander to see if this helps.

Thanks!