Quote Originally Posted by JAZZCNC View Post
No regards torque It's undisputable obviously, but I know from experience with actually using them not calculating or theorising.! . . they have more than enough torque even with the disadvantage.
It's almost impossible to have too much torque since it so directly affects machining and is so useful, and the 20mm screws enable a much greater factor of saftey than the 16mm ones, or higher feeds/acceleration if you choose that way.

When I did the motor tuning on Chip's router we got perfectly good feedrates (can't remember exactly what, long time ago). That's with similar length 16mm screws, but only 5mm pitch so nowhere near as good as 10mm pitch if you're after speed.

Quote Originally Posted by JAZZCNC View Post
If you want to go looking around the zone etc then I think you'll find more unhappy owners of long 16mm screws than you will 20mm.
Surely that is because the vast majority of people use 5mm pitch 16mm screws, which due to my reasons earlier are clearly going to cause grief.

Quote Originally Posted by JAZZCNC View Post
I know if asked to build a machine with 16mm screws of this length I would re-fuse and recommend 20mm with correct size pitch to suit the intend purpose of the machine.
Yes, naturally so would I in an ideal world where it's a reasonable price to get 10mm pitch.

Quote Originally Posted by JAZZCNC View Post
My proposal to use geared 20-05 was work around to no cheaply available 20-10 and wasn't saying they are the ideal solution
Gearing helps but you're still limited by the torque due to the high screw energy and potentially whipping. I will only ever use pulleys anyway as clearly it gets the most optimal torque and has the added bonus of reducing resonance.

Quote Originally Posted by JAZZCNC View Post
I'll take real world experinece over calculated theory any day . . . . IMO it's priceless and feel privilaged when someone shares there often hard learned experineces.
Yes experience is of course great if the situation is similar enough for it to apply. I probably lack in experience to you, but however valuable experience is, experience backed up with mechanics is indisputably a lot more useful.