Im trying to pick a screw for a machine and im stumped. I used nooks critical speed calculator and with a .5" root dimater and 48" from bearings it will give 372rpm. That seems low as this would allow for a max speed of 75 IPM with a .2 lead. I have read other posts of people running 5/8 screws at 800RPM. What am I missing here?
EDIT
Oops, I did not have the correct fixity selecte. I should be able to get around 1000rpm with a 48" screw. Does this seem like a realistic figure?