6mm ackley neck turning problem

[sdowdy]

I'm forming 6mm ack from Norma 7x57 brass. Before fire forming I'm neck turning, the necks have very small feed grooves in them. I've tried turning slow by hand and drill, even tried two passes. After fire forming and resizing with bushing dies, it appears the bushing is hitting on the high spots of these grooves.. My other non neck turned brass for .243 is shiny all around neck where bushing hits.
Any suggestions? Is this normal with turning?

 

[sdowdy]

Before fire forming brass.

 

[Preacher]

You need to be turning fast and feeding slow, really really slow.
Be sure to keep the cutter on the cool side too.........

 

[dkhunt14]

Take some steel wool and spin the case and steel wool it. This will help get rid of small lines from your turning. Matt

 

[jlow]

Take a smaller bite. The more you are trying to cut, the more passes you will need to take. The last one is always the most important to get that smooth finish and so the smallest bite. Do a pass and put the neck up to the top of your lip under your nose - if it feels warm, you are turning too fast and/or taking too big of a bite.

 

[jonbearman]

I saw p1zombie's video and he takes it all in one bite.He goes in slowly and backs out even slower by the looks of it.Out of pure curiosity,what kind of turner is sdowdy using?

 

[artbosco]

I'm forming 6mm ack from Norma 7x57 brass. Before fire forming I'm neck turning, the necks have very small feed grooves in them. I've tried turning slow by hand and drill, even tried two passes. After fire forming and resizing with bushing dies, it appears the bushing is hitting on the high spots of these grooves.. My other non neck turned brass for .243 is shiny all around neck where bushing hits.
Any suggestions? Is this normal with turning?

I see grooves like that sometimes when brass debris builds up on the cutter. I clean the cutter after every complete pass with a soft toothbrush. K&M recommended, to me, a turning speed of 180 RPMs as an ideal speed, not too fast, not too slow. Stuffing the neck into 0000 steel wool and rotating at the same speed smooths out the necks appearance. Also, fireforming with 40K to 60K psi also does a nice job of eliminating those marks.

 

[jlow]

Just because someone does it , it does not mean it is right for you. It depends on things like how deep is your cut, the type of cutter you are using (i.e. carbide or not), how sharp is your cutter, how fast is the cut. If you are having problems, that is your answer to whether it is the right method.

 

[sdowdy]

I'm using a new Sinclair cutter, I was taking .003" in beginning, tried stepping down to .001 at a time with slow multiple passes but same result. What would brass from a damaged cutter look like??

 

[sdowdy]

They appear smooth until I neck size with bushing, then it shows the spots that bushing hits. May not be a prob but could cause inconsistent neck grip?

 

[jlow]

Are you using Imperial lube? You need to lube both the turning mandrel and also the neck you are turning.

 

[snowpro440]

Some lube will take care of this ...

 

[jlow]

Lube is extremely important in neck turning. It will lubricate the interface between the turning mandrel and the neck which will significantly reduce heating. It will prevent galling on to the turning mandrel which can change its diameter. It will also allow much smoother cuts and reduce heat at the cutting surface. Turning cannot be done properly without lube.

 

[sdowdy]

Yes I was using imperial lube, but not to the extent described. I will give that a try.
I used the Sinclair expander mandrel to neck up to fit the turning mandrel, but it was not a fit that would cause galling.

 

[sdowdy]

BTW, thanks for all of the advice

 

[jlow]

Actually even if you use the correct expanded that is made to pair with the turning mandrel, you will still need to lube the mandrel because it will have too much friction. Whether it gall or not is a separate issue as the friction will cause heat and that will be a problem. When it heats up, the neck will expand, because of the expansion, the cutter will cut deeper into the neck which is something you do not want. Like I said, heat is your enemy here and you have to do whatever it takes to prevent heating but the first thing you need to do is to determine if there is heat and then figure out how to prevent heat. I can usually cut necks with consistently less than 0.0003" variance around the neck and what makes this possible is the lack of heat.

 

[mackr]

When I go from one caliber down to another I always expand (in this case 7mm) at 7mm and do a neck clean-up maybe a thousand and then neck down to 6mm and expand to 6mm and do my final trim, two thou at the most.
(Sinclair expanders and pilots and the big Sinclair 4000 turner)
Mack

 

[sdowdy]

I received my new 7X57 brass and gave it another try. For whatever reason the brass fit tighter on the mandrel which fixed the problem. Only thing I changed was skipping my 1st sizing pass through the .243 die. I went straight to the 6mm. I also lubed the mandrel better. Thanks for help!