Re: SFM Question
Hi 55th,
When turning smaller diameters (generally <.125", and especially when you get <.050") SFM calculations begin to break down as a hard and fast rule. We also have citizen M's and in my experience turning small diameters of .020-.050, I generally find that 4000-6000 rpm works best, even though the SFM may calculate out to be very low. I cant tell you exactly why this is, its just what I have observed over time across many jobs, materials, tools, inserts ect. When turning faster, I sometimes see smearing/chip re-weld, bar vibration becomes excessive, or the high point on the insert burns up quickly (if taking a larger depth of cut the largest diameter on the insert sees a much higher SFM than the cutting point)
So anyways, I see 300-800 sfm on many inserts now days, but cant imagine trying to hit 600+sfm even if we had a 16k or 20k spindle. I would bet that unless your barfeeder is specifically designed for high rpms, the higher speed will produce other problems that outweigh any benefits. When a speed calculation gives you a huge number like 28k, just try something in the 3000-6000 range and see how fast you can go without other problems developing. Speeds from 50-250 sfm are much more practical at small diameters.
CNC Product Manager / Training Consultant