What's new
What's new

CNC milling help with longer end mills step over and depth of cut calculations


Apr 21, 2024
south africa
Good day I'm a machinist from South Africa I'm moving to a new company so I need to adjust and update the information on tooling and cutting depth and feeds and speeds. So I would like to find out like how do you guys calculate feed and speeds on long end mills. So the new company uses Kennametal and other good brands of tooling and I see they try to stay up to date with tooling but it looks like the old CNC programmer beat around the bush. Like I want to show the boss I can outperform his current tooling with normal HSS C08 end mills yes literally like they let me use an 16mm diameter solid carbide +- 200mm long to cut a hole of 22mm * 75mm * 9mm deep on En24T steel like I would literally cut faster with standard short HSS end mill than solid carbide. In this case I will just plunge the 16mm end mill 8mm deep on standard short HSS end mill and it would take like 2 cuts and I'm finished. I'm not saying HSS is faster I'm saying the length of the cutter matters. Or am I wrong about this? So how would I calculate the step over like lets say I have a 200mm long cutter and want to use the whole 200mm how would I go about this. there must be some type of formula that includes the tool length. because I still work on the basics of half tool diameter depth of cut full feeds and speeds on standard length end mills.
This is how:

Yes, the length of the cutter does absolutely matter. The deflection in the cut will go up with I believe the third power of the length of the endmill, for a given diameter. Use the shortest endmill you can for the cut.
Last edited: