New Sinclair Neck Turner Question

[nickster]

I have a Sinclair neck turner and it looks like the angle on the cutter is off for my 6BR Norma brass. My choices for the new cutter are 30 and 40 degrees at Brownells. I looked at the schematic of the 6BR on our site and the shoulder angle is 60 degrees so I assume that I would need the 30 degree cutter?

 

[Rank Amateur]

IIRC, the standard cutter supplied with the Sinclair tool is 30 degrees. Sinclair also has a 40 degree cutter. You should actually be able to use either for 6BR depending on how much you cut into the neck/shoulder junction, though the 30 degree blade might make a wider/smoother cut into the shoulder...

 

[AlNyhus]

A cutter with more angle than the case shoulder will give a smoother blend into the shoulder. -Al

 

[nickster]

The present cutter cuts into the neck before it reaches the base of the neck/shoulder. I bought the stuff used years ago and am just trying to use it now. It might have been used on a .223 because some of the mandrels were small. I don't know what angle cutter they might use. I know I don't want to use the one that's in it. Will a 30 degree cutter work for the 6BR round?

 

[Rank Amateur]

A cutter that has exactly the same angle as the shoulder will cut a ring into that shoulder the width of the cutter blade face, leaving a sharp ring outside that diameter. So, the neck/shoulder junction will look like it is cut properly, but that sharp ring in the shoulder can be a weak spot. A cutter with a larger angle seems like it cuts into the neck/shoulder junction deeply before the cut into the shoulder itself “widens out”. The advantage of this is that the transition between the cut and uncut surfaces of the shoulder is always gradual. Downside is that if you try to cut a wide ring in the shoulder, you may cut too deeply into the neck/shoulder junction leaving a weak spot. Hard to describe, but look at the graphic of various cutter angles/various shoulder angles on the K&M site for a visual. I’m not a fan of the K&M tool, but the graphic is useful.

Neck Turner Cutter K+M Precision Shooting Products

Neck Turner Cutter | Best Tool Steel and Carbide Neck Turner Cutters for Neck Turning Reloading | K+M Precision Reloading Tools

kmshooting.com

If using the 30 degree cutter for a 30 degree shoulder, don’t cut into the shoulder deeply. If using the 40 degree blade, limit cutting into the shoulder so that the width of the cut into the shoulder is roughly 1/2 the width of the blade face itself. Hope this helps...

 

[ricco1949]

Re-Grind it yourself using a digital protractor to set the grinder angle.

I set it for 1-2° more than shoulder angle.

That will allow a full cutter width cut with only a slight cut into shoulder.