Re: Trying to cut .043 slot in 01 tool steel breaking endmills Help
A difficult project. A wire EDM would be my first choice for this job, but I'm assuming you don't have one in your back pocket.
O1 tends to work harden if you don't have enough feed speed. But using a 0.043 endmill limits tooth load, I think cobalt is a good choice. Right now at 2000 RPM and 3 IPM translates to a surface speed of 23 FPM and 0.0008 tooth load (assuming a 2 flute end mill). My gut says that you are turning way too slow for a 0.043 end mill and should be up around 6000 RPM, about 60 SFPM in O1, but I have no data to back this up. I have cut quite a bit of O1, but never with an endmill that small.
I would try drilling a series of ~1 mm holes to remove as much material as possible then maybe plunge mill with the endmill with about 20% step over. Then run a finish pass to complete. I don't know if Fusion has a plunge milling cycle, but you can manually make that happen, even hand code the cycle if needed. Using a 0.043 endmill in a 0.043 slot eliminates the possibility of using adaptive clearing so you are going to have to get creative.
Jim Dawson
Sandy, Oregon, USA