Chipping Carbide

[Sean Yaw]

I used a brand new 1/2" carbide endmill from HTC Tool to mill four reliefs in brass slipjoint liners. I was running the end mill at 1340 RPM (per the Little Machine Shop speeds and feeds calculator) and used a rotary table. I did not use any coolant/lubrication so that I could more easily see the lines I was aiming to cut to. After just those four cuts, I am seeing chipping on the cutting edge, near the tips (but not on the actual tips). It is hard to get a good picture, but you can see the divot on the cutting edge most easily on the tooth in the 10:00 position. That same divot is on all of the teeth. Is there anything obvious that I am doing wrong? Thanks

 

[AVigil]

is that a "corner radius" end mill?

 

[Sean Yaw]

is that a "corner radius" end mill?

Yes, it is.

 

[AVigil]

Use lubricant.

 

[tinfoil hat timmy]

That should still cut for a while. I'd use lubricant and not worry too much about it.

 

[nhobo]

That is not chipping, it is the ground shape of the cutter. Most brass is leaded and free machining.

 

[Sean Yaw]

That is not chipping, it is the ground shape of the cutter. Most brass is leaded and free machining.

Shoot! You are right. I looked at an unused one and it has the same "divot". Dumb thread of the weekend finished.