This might help and please correct I'm if I am wrong.
mim move = lead of screw / steps per rev of motor:
1/2-10TPI ACME has a lead of 0.1/200 spr(typ) = 0.0005" travel per step of motor
1/4-16TPI ACME has a lead of 0.0625/200 spr(typ) = 0.0003125" travel per step of motor
1/4-20TPI ACME has a lead of 0.05/200 spr(typ) = 0.00025" travel per step of motor
Add in microstepping from the driver and you can see that the travel from 1/2-10 ACME will have more than enough resolution for a home build MDF machine and the speed increase will be: 50% over the 20TPI and 37.5% over the 16TPI.
I think the slight increase in cost for 1/2-10 is more than worth it.
I hope all my calculations are correct and everything I have said is right, can someone confirm.
Robin
A much wittier reply came to mind immediately after I clicked the 'Send' button