What good is SFM?

[Travis_Buchanan]

OK, Ive cut a lot of materials including some aluminum over the last 20 years on cnc equipment but have yet to wrap my head around SFM. Ive been cutting aluminum with a solid carbide 1/2" end mill that says 1200 SFM but Im cutting good at 15k rpm, .15 doc, and 200 ipm which is 1960 sfm. When does the sfm really matter? Is it when your 1*D in depth?

[Guest CNC Apps Guy 1]

It's just a starting point. I routinely exceed tool SFM recommendations by double digits

[Bruce Caulley]

The same cutting speed (SFM or M/min) is taken from the lowest valley of a tool performance graph based on controlled cutting conditions. Since these grapghs usually look like an ECG scan there are areas that exceed the recomended cutting speed by sometimes 400% or more. The tool supplier will never print a catalogue with those conditions in it and simply use the lowest achievable under all usual conditions to be safe.

 

Bruce

[Travis_Buchanan]

Thanks Guys, Ive got a terrible demo right now on 3" thick extruded 5000 series aluminum. Some of the ribs are just flopping in the wind with no rigidity. And of course it has got to be done fast. Why do they give me these crazy parts?

[jeff]

It matters more when you are using it on a lathe.

But as said above, it's just a starting point, and since you're cutting aluminum, I've found that most tool suppliers' SFM specs are way low.