Hey,
Touché. Your speed calculations are correct. Speed can be over rated. My main point was that the screw will probably not be the concern for accuracy. Other flex and looseness in the system will be.
Seeing other home built machines around here, 150 ipm is very good, and this is usually just used for rapids. More like 50-80 for cutting. The 10 tpi screw will work very well. But the 4 tpi screw will allow you to stay down in the torque curve, give you more speed for a given rpm, give you less whip for a given speed, not cost much more, not affect your accuracy, and a 2 start is more efficient than a 1 start. IHMO.
More important is to actually build a machine.
Steve |