Making a profile cutter

[pbarratt]

I am trying to use my CNC mill to make profile cutters for cutting special shape grooves in the edge of steel discs. I'm using 1/4" square tool blanks.

I've tried using a small grinding stone in my high speed spindle adapter. I've also tried a carbide burr in the same spindle. In both cases, I get excessive heating. The spindle operates at 28,000 RPM. The stone is about one inch in diameter. The burr is about 3/16" in diameter. I've tried feed rates of about 20 mm per minute, depths of about .02mm per pass with the stone and .05mm per pass with the cutter.

The cutter profile has only convex curves.

I only need to make about 3 or 4 grooves per cutter.

Anyone out there with some experience in this?

Thanks

[Delw]

I am going to guess your going too fast maybe too deep.
if there is a way to add coolant to this it might help. however grinding stone grit is very bad for a cnc machine so you will need to find a away not to get any grit anywhere.

is there a way to rgh them with a surface grinder or by hand with a grind wheel? then you can finish with cnc mill.

[Delw]

oh yeah dont forget fine stones will heat up faster than coarse stones.

[pbarratt]

Delw,

Thanks for the reply.

The tip on the grade of grit may help if I stay with a grinding approach however the stone I'm using seems like it's rather coarse. It's a stone for a die grinder.

Coolant doesn't seem like an option with grinding, especially at 28,000 RPM. Maybe with the carbide cutter but even then it would be messy.

I figured the carbide burr had a better chance but the thing began to glow even with a slow feed and what I thought was a light cut. The width of the cut wasn't even the full depth of the blank as I had not progressed that for yet. For explanation, I'm using a tapered burr to get a relief angle under the cutting edge. The stone was tapered also.

Tomorrow I'll get a new carbide cutter and try again with a lighter cut.

Thanks

Pete

[Delw]

Put the coolant on the part below the stone, dont have it hit the stone at all cause thats not only a mess but can cause major out of balance on the stone at 20+k.

Delw

[pbarratt]

Hmmmm, I can't quite envision that. The tool being shaped is a 1/4" square tool blank and the profile is being cut from the sides and goes around from one side, around the end, and on the other side making a shaped, 'point', with a shaped end and tapered sides. There is no part below the stone.

I wonder if I should try the carbide burr at 'normal' spindle speeds and an extremely slow feed and shallow cut less than .001". Time is not a problem.

Pete

[Delw]

Sorry I was thinking you were cutting a groove in one end and letting the end that you hold be surrounded by some type of coolant.
dont know about the speeds on carbide burr as I only used them in flooded coolant for one set of parts on alum to keep me from surfaceing the entire part. had a real cutter made once it was proven out. I know they load up fast if you go to fast on feeds even with flooded coolant on alum.

[pbarratt]

Thanks again. I'll chew on this some more.

Pete