K&M Neck Turning Oddness

[sawacs]

Last year I purchased a KM neck turning tool mainly for use with 260 and 6.5-284 brass. Since I am a little ignorant about the results, I thought I would ask the experts here

After turning the neck, on say a 260 case, I noticed that the tool creates a sharp ridge where the neck and shoulder meet. Now I have seen photos where the turning tool actually turns a portion, ever so slightly, of the case shoulder rather than creating a sharp edge (looks like the neck and shoulder junction are blended nicely). I am wondering if the angle of the cutting tip is at a different angle that the case neck. Logically, this should be the case and according to my observations this is the case.

Is there any reason I need to turn down into the case neck and shoulder junction other than to rid the brass from the horrible tasting donut? Wouldn't I be achieving the same goal by backing off of the cutter length so it does not touch the case shoulder?

According to my Hornady manual, the 260 case shoulder is 20 degrees. Does anyone make a neck turning cutter with 20 degrees built in for the 260 shoulder?

Thanks,

Shawn

 

[jonbearman]

PMA has different angles ground into their tools. I would call K&M and see if they do or will.

 

[Milo 2.0]

21st Century has the angled cutter you need.

 

[Martin52]

... I noticed that the tool creates a sharp ridge where the neck and shoulder meet.

Thanks,

Shawn

Are you cutting too deep into the shoulder ? The cut length can be adjusted on the K&M by adjusting the mandrel. The cut should be around 1/32 into the shoulder, a deeper cut might be causing the sharp ridge.

 

[sawacs]

I cut deeper than normal on a scrap piece of 260 brass to see what would happen. I would prefer the neck shoulder junction to blend rather than create a ridge. Since I purchased the KM stuff to start, I sure hope the other cutters will fit or I will have to scrap the KM and change over to something else.

Thanks for the information!

Shawn

 

[ireload2]

Ideally the cutting tool should have a corner radius that matches your brass and the leading edge rake should match the shoulder angle or be slightly sharper so the cut feathers out up the shoulder.

Any machinist or tool maker familiar with free hand grinding of lathe tools can grind and hone those tool bits. That skill goes along with being able to run a lathe. The manufacturer of the tool may be able to supply what you want too.

 

[DocBII]

sawacs,

K&M used to sell cutter blades for different shoulder angles. Check with them to see if they still sell them. The reason for cutting into the shoulder is to keep donuts from forming. These can be cut out with the carbide mandrel, or ignored if the boattail doesn't go past the neck/shoulder junction.

HTH,
DocBII

 

[DOGCAPPER]

The K&M cutter can be matched to your shoulder angle. The cut should run out slightly onto the shoulder. After several firings the cut will burnish out or blend into the brass and become invisible. LT

 

[sawacs]

Much appreciated for the information.

I spoke with Roger at KM and got everything cleared up. I am simply going to adjust the cutter so the case shoulder is barely touched. The end of the mandrel also has a cutter built in to solve the donut problem.

Thanks,

Shawn

 

[jsthntn247]

Much appreciated for the information.

I spoke with Roger at KM and got everything cleared up. I am simply going to adjust the cutter so the case shoulder is barely touched. The end of the mandrel also has a cutter built in to solve the donut problem.

Thanks,

Shawn

The cutter on the end of the mandrel solves the problems after you get problems, not prevents them. It also requires a second turning process. I would see if I could get the right angled cutter for your shoulder and not get problems in the first place.