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Varying neck wall thicknesses after neck lathing

Please will you help me?

I am using the K+M neck lathing kit. The K&M mandrel is a snug fit into the neck of the case and I am using a graphite based grease with some STP additive mixed in. (Very slippery)

I am using hand power to perform the operation.

The cases that I am presently about to neck turn are some once fired donated .308 Peterson Lapua Palma's which have been full length resized, trimmed, chamfered and de-burred. The cases that I am practising on are from the same batch.

I am using the Sinclair Digital Thickness Gauge to measure

What I don't understand is why there is always a variation between the neck wall thickness at the shoulder (typically .014) and at the neck end (typically .013 to .0135) These measurements were only taken at points where the lathe had effected the metal.

1/2 a thou I can accept, but a full thou I don't understand.

What am I doing wrong?

Many thanks in advance.

EDIT:-

I THINK I may have the answer to my question. I have been trying to take too much off too fast.

The thickness at the shoulder was .014. I deepened the cut by .0004 and now I am getting a consistent .0135 where the brass has been effected.

I any of you have any more advice, I would still appreciate it.
 
Last edited:
Sounds like you are on the way. Yo might try slowing down your feed rate a little. Be sure and keep the mandrel cool. Carry on.:D:D

Paul
 
Sounds like you are on the way. Yo might try slowing down your feed rate a little. Be sure and keep the mandrel cool. Carry on.:D:D

Paul

Hi Paul

Many sincere thanks for your help/encouragement.

By Jove, I think I have nailed it!! (only about 10 hours later):D

By using hand power only AND a slow feed rate I get a VERY consistent .0135 at all cut surfaces.

At .0135 approx. 80% of the cases' necks are effected. I've just advanced the cutter by .0004 and have redone a couple of my practice cases. At .013 dead, 100% of the cases' necks are lathed.

Thanks again.

Cam
 
Something else, you need to undersize the neck and let the K&M expander bump it back out to the proper side for the turning mandrel. If the necks were real close to the right size to turn, the mandrel may not be able to make them 100% round. Also some brass is springy may be more difficult to get round and may need annealed first.
 
The cases that I am presently about to neck turn are some once fired donated .308 Peterson Lapua Palma's which have been full length resized.

I any of you have any more advice, I would still appreciate it.

Should be using a full length, NON BUSHING die...in case you aren't.
 
Hi Y

Interesting! I always f/l resize, but why do advise using a non bushing die?

Many thanks

Cam
I think hes saying to use a traditional full length for prior to turning, not all the time.
The bushing leaves the bottom of the neck unsized like on the right side.
ts260rawshoulderx600.jpg


If you turn the necks with that unsized portion you will take off more there at the bottom than the rest of the neck.
 
1/2 a thou I can accept, but a full thou I don't understand.

What I don't understand is why there is always a variation between the neck wall thickness at the shoulder (typically .014) and at the neck end (typically .013 to .0135) These measurements were only taken at points where the lathe had effected the metal.

Did you measure the thickness of the neck before you started? There are things that happen when cases are fired that can not be discussed on a reloading forum.

F. Guffey
 
I think hes saying to use a traditional full length for prior to turning, not all the time.
The bushing leaves the bottom of the neck unsized like on the right side.
ts260rawshoulderx600.jpg


If you turn the necks with that unsized portion you will take off more there at the bottom than the rest of the neck.

The cases were resized with a .337 Nitride bushing (which gives a good snug fit on the K&M mandrel)

After turning, I have measured at least 100 cases at various points on the neck (shoulder area to neck end) and I am getting a very consistent .013.

TBH, I cannot discern any difference in the above mentioned cases, but sincerely thank you for taking the time to photograph same!
 
Errrr, you have lost me!!!!

Not my intension, there are many members on this forum that do not know and 'whoa' be onto anyone that offers to help. When it come to the neck thickness I have 3 categories and not one of the categories that has to do with neck turning.

F. Guffey
 
I think hes saying to use a traditional full length for prior to turning, not all the time.
The bushing leaves the bottom of the neck unsized like on the right side.
ts260rawshoulderx600.jpg


If you turn the necks with that unsized portion you will take off more there at the bottom than the rest of the neck.

Yep, that's what I was saying. Thanks for the picture and explanation to the OP.
 
What I don't understand is why there is always a variation between the neck wall thickness at the shoulder (typically .014) and at the neck end (typically .013 to .0135) These measurements were only taken at points where the lathe had effected the metal.

Brass is drawn from a cup shape to form the case. It is near impossible to have a uniform thickness of the walls. A taper from top to bottom is normal for the process.


deepdrawop.gif

rwsdrawchartx350.gif

http://bulletin.accurateshooter.com/tag/case/
 
Not my intension, there are many members on this forum that do not know and 'whoa' be onto anyone that offers to help. When it come to the neck thickness I have 3 categories and not one of the categories that has to do with neck turning.

F. Guffey

Are you feeling ok Guffey?
 
When it come to the neck thickness I have 3 categories and not one of the categories that has to do with neck turning.

Ratbuster, is that all you could come up with? I said I have three categories of necks that seemed to be a problem for reloaders and I said not one of the three has to do with turning necks.

F. Guffey
 
The cases were resized with a .337 Nitride bushing (which gives a good snug fit on the K&M mandrel)

After turning, I have measured at least 100 cases at various points on the neck (shoulder area to neck end) and I am getting a very consistent .013.

TBH, I cannot discern any difference in the above mentioned cases, but sincerely thank you for taking the time to photograph same!
Because of brass spring back, the expander is not always going to expand each and every case out the same. So turning that case that was sized with a bushing die could produce a thin area there at the neck/shoulder junction. Sounds like you figured out not to take too much cut. When I get to the final cut, I take .0005" at a time to get there.
 
None of your replies make any sense. We are not stupid.
Ratbuster, is that all you could come up with? I said I have three categories of necks that seemed to be a problem for reloaders and I said not one of the three has to do with turning necks.

F. Guffey

Mr Guffey

Given that I am a relative newcomer to precision reloading your answers are cryptic and, frankly, are not helpful.
 

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