KM neck turning tool question

[TommyD11730]

So I thought I was being "smart" when purchasing the KM arbor with the donut cutter. I have noticed the inside necks now resemble the grooves found on a record. Both the 30cal and 223 mandrel do this.
I can't see how this would be a good thing. Would this not cause changes in neck tension?

 

[DIBBS]

Are you using a quality lube on the mandrel? Any brass buildup on the mandrel? How hard do the cases turn? It shouldn't be scratching/gouging in inside of the cases. I would recommend the imperial sizing die wax or maybe it's redding now. (even if you purchased a carbide manderel)

A little tin-o-wax goes a LONG ways.

edit: reading and comprehension are important. I thought OP was getting scratches from the outside neck turning process. Oh wells.

 

[spife7980]

OP- Are you using the smooth mandrel or are you using the cutting pilot?

Or

Im going to assume its the cutting pilot which is an inside reamer which IMO is the worst idea of all time. Ill never spin a cutter inside of the necks. Hell, Ill never spin anything beyond a nylon neck brush inside.

 

[IHFarmer07]

Yeah, you have to be damn careful inserting the donut cutting mandrel into the neck. If it’s a wee bit crooked the results you have on your picture is what you get.
I’ve got brass I done this to too, just shoot it. If it’s for competition shooting use as fowlers or something.
Honestly if you are turning the necks correctly you shouldn’t need those mandrels. Next time I buy another k and m I won’t buy the inside cutter mandrel either. Turning the necks just a bit into the shoulder WILL solve the donut issue and you won’t need the inside cutting mandrel.

 

[TommyD11730]

OP- Are you using the smooth mandrel or are you using the cutting pilot?

Or

Im going to assume its the cutting pilot which is an inside reamer which IMO is the worst idea of all time. Ill never spin a cutter inside of the necks. Hell, Ill never spin anything beyond a nylon neck brush inside.

Correct, it's the inside cutting mandrel.
I shot KM an email, waiting to hear back.

 

[TommyD11730]

Yeah, you have to be damn careful inserting the donut cutting mandrel into the neck. If it’s a wee bit crooked the results you have on your picture is what you get.
I’ve got brass I done this to too, just shoot it. If it’s for competition shooting use as fowlers or something.
Honestly if you are turning the necks correctly you shouldn’t need those mandrels. Next time I buy another k and m I won’t buy the inside cutter mandrel either. Turning the necks just a bit into the shoulder WILL solve the donut issue and you won’t need the inside cutting mandrel.

I can't see , by the very nature of the tool (it never spins 100% true how you can avoid this.
I'm ready to take a file to the cutter portion of the mandrel.

 

[IHFarmer07]

I can't see , by the very nature of the tool (it never spins 100% true how you can avoid this.
I'm ready to take a file to the cutter portion of the mandrel.

I push it in as far as I can by hand. I have the case holder in the drill with the case, I rotate the k and m tool(by hand backwards so it’s not gouging the inside of the mouth), then once it’s in the case neck as far as I can get it I then stop and then start the drill. I use an alcohol and lanolin mix for a case lube and some of that gets inside the neck for lube for the mandrel. The mandrel is carbide so it’s not supposed to gall unless it’s not expanded the correct size. The only time I get those marks in the neck is when I’m careless about inserting the tool not perfectly square into the mouth and extracting the tool perfectly square. I’m sure it has some effect on the bullet release and on target but I haven’t seen enough of an ill effect for me to be up in arms about. Every time you fire the round the marks will be less and less.

 

[TommyD11730]

I push it in as far as I can by hand. I have the case holder in the drill with the case, I rotate the k and m tool(by hand backwards so it’s not gouging the inside of the mouth), then once it’s in the case neck as far as I can get it I then stop and then start the drill. I use an alcohol and lanolin mix for a case lube and some of that gets inside the neck for lube for the mandrel. The mandrel is carbide so it’s not supposed to gall unless it’s not expanded the correct size. The only time I get those marks in the neck is when I’m careless about inserting the tool not perfectly square into the mouth and extracting the tool perfectly square. I’m sure it has some effect on the bullet release and on target but I haven’t seen enough of an ill effect for me to be up in arms about. Every time you fire the round the marks will be less and less.

Thanks for typing that out. I think I'll just order a couple non cutting steel mandrel's and going fwd over lube the necks when turning.

 

[TommyD11730]

Well 0000 didn't remove the scratches. Had to wrap a tiny dowel in 220 sand paper and work my way up to 2200. Polished out nice.
Still have between 1.5 and 2 tho tension. In hindsite I should have mic the necks. I figured being I didn't change my tension I couldn't have removed much material.
Marked the rounds accordingly and will report how they shoot. Might be a couple of weeks though.... oh will also report back what K&M has to say.

 

[IHFarmer07]

Well 0000 didn't remove the scratches. Had to wrap a tiny dowel in 220 sand paper and work my way up to 2200. Polished out nice.
Still have between 1.5 and 2 tho tension. In hindsite I should have mic the necks. I figured being I didn't change my tension I couldn't have removed much material.
Marked the rounds accordingly and will report how they shoot. Might be a couple of weeks though.... oh will also report back what K&M has to say.

I did that on a few before, polished to a real nice shine. They had an insane amount of grip on the bullet though, those 5 pieces of brass I did that to had the best shot to shot velocity number I’ve ever seen out of that rifle, the es and sd’s were less than 5fps and I think it grouped good to. Thats too much work though lol. The whole neck tension deal is a long drawn out rabbit hole. You can size the neck to whatever interference fit you want but the bullet will always stretch it to fit. How much the grip is inside the neck probably has more of a bearing on the release of the bullet than any, but it also depends on annealing or no annealing and if you annealed the brass not enough or too much, lot and lots of factors!! The es/sd’s will show that.

 

[Tokay444]

How did you come to the conclusion that you have donuts, and that they are causing you problems and need to be removed?

 

[TommyD11730]

How did you come to the conclusion that you have donuts, and that they are causing you problems and need to be removed?

I didn't. My theory was buy once cry once. Buy the all in one mandrel vs just the standard one. Unknown to me I would have problems as a result of the cutter.

 

[TommyD11730]

I did that on a few before, polished to a real nice shine. They had an insane amount of grip on the bullet though, those 5 pieces of brass I did that to had the best shot to shot velocity number I’ve ever seen out of that rifle, the es and sd’s were less than 5fps and I think it grouped good to. Thats too much work though lol. The whole neck tension deal is a long drawn out rabbit hole. You can size the neck to whatever interference fit you want but the bullet will always stretch it to fit. How much the grip is inside the neck probably has more of a bearing on the release of the bullet than any, but it also depends on annealing or no annealing and if you annealed the brass not enough or too much, lot and lots of factors!! The es/sd’s will show that.

I only made 10. Hadn't planned to crono them... maybe I will now.

 

[Tokay444]

I didn't. My theory was buy once cry once. Buy the all in one mandrel vs just the standard one. Unknown to me I would have problems as a result of the cutter.

So you’re trying to fix a problem you don’t even know you had, and thusly have created another problem.

 

[TommyD11730]

So you’re trying to fix a problem you don’t even know you had, and thusly have created another problem.

You have just summed up my life with your post. Well done Sir.

 

[TommyD11730]

From K&M
Thanks for reaching out. The cutting pilots can be used successfully without grooves in the case neck. Here are a few tips:

• Before spinning the cartridge, insert the case on the pilot as far as possible
• Ensure the case stays square to the pilot during the turning operation

As for the cases with grooves, it’s worth a try with fine steel wool or similar abrasive to clean them up.

 

[gixxer822]

You may need KM mandrel to expand more

 

[IHFarmer07]

From K&M
Thanks for reaching out. The cutting pilots can be used successfully without grooves in the case neck. Here are a few tips:

• Before spinning the cartridge, insert the case on the pilot as far as possible
• Ensure the case stays square to the pilot during the turning operation

As for the cases with grooves, it’s worth a try with fine steel wool or similar abrasive to clean them up.

Huh, interesting.

 

[IHFarmer07]

You may need KM mandrel to expand more

I use a Kenny Porter die with pin gages. Lol there’s an infinite amount of sizes to use with it!

 

[TommyD11730]

So USPS had today marked to deliver my new mandrels.... well you know how that goes. So anyways I grabbed 3 pieces of LC brass that I didn't care all that much about. Like IHFarmer mentioned I slid the case onto the mandrel without rotating. Make my cleanup passes, then removed the mandrel again without turning the brass.
Yep, no grooves, lesson learned.
Thanks Brother.

 

[IHFarmer07]

So USPS had today marked to deliver my new mandrels.... well you know how that goes. So anyways I grabbed 3 pieces of LC brass that I didn't care all that much about. Like IHFarmer mentioned I slid the case onto the mandrel without rotating. Make my cleanup passes, then removed the mandrel again without turning the brass.
Yep, no grooves, lesson learned.
Thanks Brother.

No problem bud! Lol I did say to rotate in the opposite direction of neck turning to put the brass on the mandrel but hey, if it works for you without rotating the brass to put on and take off awesome for you!

I’ve got a couple of these k and m’s with this option, so I know what your dealing with and how to get around it. It all takes a learning curve.