I'm not an expert, but here goes.
There are not hard and fast rules, it depends upon many factors, machine speed, lead screw pitch, screw diameter, are you turning the screw or the nut? Is the shaft supported in the middle?
In my opinion, a 5/8" screw with a .2" lead will not work well on a 72" long router without additional considerations. I have a 30" machine and with rapids of 180" per minute. The screw is starting to whip so that's probably about max for me.
180" per minute is very fast on a small machine, but on a 72" its pretty slow.
There are posts on the forum that discuss spinning the nut and keeping the screw still. That might be your best bet.
I would think that you would need a bigger lead, say .75" with a 1" screw to get decent performance on a 72" machine.
Pure speculation on my part. |