[project5k]

here is a little chart that i keep looking at.....

i would suggest figuring out what you really want/need your rapid speed to be and then figure it from there..
if you need 100IPM, then a 10tpi screw may not be for you...(it would have to spin at 1000 rpm) now if you wanted something like 50ipm, then you might get a 10tpi screw to work at 500prm, given that its the right thickness.. the general rule is the longer it is the thicker it needs to be, and the faster you wanna spin it the thicker it needs to be....

for my rig, im gonna use 1/2inch screws, 10tpi, and at 72 inches long i cant really spin them any faster than 400 rpm, so thats 40 IPM travel... if i spin the screw that is... if i spin the nut, then i can spin it much faster and not have shaft whip...

the other thing to consider is the amount of thrust you will be applying to the screw.. if you have a big heavy gantry, then that will apply more force to the screw than a smaller lighter one, and so the thickness of the screw will play into how fast and hard you can shove the axis around...what im finding out is that this is just like that like from Mad Max.. speed is just a question of money, how fast do you want to go???