Quote Originally Posted by Jonathan View Post
Perhaps, but you can't deny the simple calculations I did in the previous post demonstrate a significant torque disadvantage from using a bigger screw with lower pitch.
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.



Quote Originally Posted by Jonathan View Post
The calculations of critical speed may not mean as much as they imply, but I feel they mean more than nothing and give a good basis.
Yes to a small degree but simply too meny variables to explicitly say that 16mm are the best by far, to the point of dismissing the others completely.

I tend to work and put more value in experience than calculations and I know from my own experiences with helping others that long thin 16mm screws give more grief than the same length 20mm.
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.

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.

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 just an easy one that I know works thru practicle hands on experience. . . . The right pitch for the job wins every time but theres always other ways to skin a cat.

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.