.060" Carbide End Mill = broken after second pass =HELP

[Janderso]

Question for you smart-experienced guys

I ordered a .060" carbide end mill from McMaster. It has a 1/8" shank with a 1/2" length of cut.

I immediately realized I was running way too slow at 2,500 rpm. I'm hand feeding very slowly.

What RPM would you run? I can go as high as 4,800 but it's in the red zone on the mill. 3,000 is safe. Too slow?

The material is annealed A2. I already eased the cut by using a .032" slitting saw thinking this would help to not break the end mill
$35 down the drain. Grr$%^&*(!!

I know, why not use a slitting saw?? I just ordered a .062" from McMaster.
I want to learn from my mistake.

If you could enlighten me with any tips that come to mind you would make my day.
Thank you,

Jeff

 

[Nutfarmer]

Looks like a normal day for me. I understand your frustration

 

[benmychree]

Yes, I would have used a slitting saw, it would never occur to me to use an end mill, I would also have considered using the bandsaw.

 

[twhite]

I use 1/16” and 1/32” at work. I spin them at 7500 slow shallow cuts. Any variation and they will snap. Plenty of coolant flow or air to keep the chips out is a must. Go with the slitting saw for that operation.

I also will use shorter end mills and go to the longer once I reach the bottom.

I


Cutting oil is my blood.

 

[Janderso]

I use 1/16” and 1/32” at work. I spin them at 7500 slow shallow cuts. Any variation and they will snap. Plenty of coolant flow or air to keep the chips out is a must. Go with the slitting saw for that operation.

I also will use shorter end mills and go to the longer once I reach the bottom.

I


Cutting oil is my blood.

I was just about to add a mister with enough pressure to blow out the chips.
Dang.

 

[mmcmdl]

You broke it because you needed to grind up a small boring bar , we know that . Other than a few $$$ down the drain , no harm was inflicted to the part . Yes , the slitting saw is the tool to use for that .

 

[twhite]

I was just about to add a mister with enough pressure to blow out the chips.
Dang.

That and maybe .005 max depth cut. You must be overly cautious. Do you have power feed? If so you might want to do 3500 rpm and slow steady feed. By hand will be a challenge.


Cutting oil is my blood.

 

[Janderso]

Yes, I would have used a slitting saw, it would never occur to me to use an end mill, I would also have considered using the bandsaw.

The only reason I went to an end mill was that I noticed the saw did not cut straight. I was hoping to salvage the cut. The first attempt was a saw, it was .062” wide. It made it about 1/8” Deep and quit.
The first slitting saw must have got dull because it quit cutting, started smoking and I noticed it got hot. Maybe the reason the thinner blade cut crooked is due to a localized work hardening issue which caused some deflection.

 

[GeneT45]

If you're super-patient you might be able to get there with 3000 rpm. I've done it, but it's walking on eggshells and I just plan on breaking at least one - and I usually do. There's just no feedback - pressure or sound - and then they're gone. I think you might have made things harder with your slitting saw cut by making it an interrupted cut. The issue isn't chip loading it's just the feed putting side load on the endmill.

GsT

 

[Janderso]

That and maybe .005 max depth cut. You must be overly cautious. Do you have power feed? If so you might want to do 3500 rpm and slow steady feed. By hand will be a challenge.


Cutting oil is my blood.

Whew, I think I had a .015” depth. Ok, lessons learned.
I do have power feed. The consistency of a slow feed using power would probably be better fir sure.