1/8 EM in 4140A, drill corners or not?

[honeybunches]

I have an inner profile that requires the corners be finished with an 1/8" EM, following a 3/8" EM. Material is 4140 Annealed. I have had plenty of problems trying to cut steels with 1/8" EMs. I think I drilled the corners before with 1/8" EM to reduce the load in the corners but it wastes a lot of time.

 

It is programmed right now to do full depth (.300) and run multi passes with about 15% radial engagement. I would prefer to remove the drilling unless absolutely needed. I am sure I could add passes but at some point, it started to make more sense to drill since that is where the tool would break, in the corner.

[LancoUSA]

Could you try a Dynamic rest mill in the corners to remove most of the material? I just milled a 2mm slot on 4140 rc 28-32 with a .070" endmill I bought 10 endmills, I have used one.

[Goldorak]

Could you try a Dynamic rest mill in the corners to remove most of the material? I just milled a 2mm slot on 4140 rc 28-32 with a .070" endmill I bought 10 endmills, I have used one.

 

 

x1000 dynamic toolpath for small end mills is a must, we do a lot of pockets with corner smaller than .250 ans dynamic was a huge improvement on tool life and reducing cycle time

 

for 1/8 endmill , try 5 to 8% stepover, it will cut forever

 

edit: don't be cheap on tooling quality