Ballscrew size -vs- project size

[Alan T.]

Is there a hard fast rule on the diameter of the recommended ballscrew or leadscrew versus the size of the machine it's being used for. I would assume that a true bench sized mill would use a 3/4in screw. What size screw should be used for a router, say 48" x 72". Could you get by with a 5/8" screw or would you get too much whip and deflection.

[buscht]

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.

[Alan T.]

Thanks for the reply. Thats about what I expected but wanted a more educated (than me) answer. I might reduce the work envelope and keep the screws to 3/4 in.


Thanks,
Alan

[ger21]

Go to http://www.nookind.com/ball/BallCatalog.cfm and look in the technical sections of their catalogs. They should have charts showing critical speeds and load capacities for all their different size screws. Lots of good info in all their other catalogs as well.

[Alan T.]

Thanks,

That was a great source of information. Unfortunately I have a headache from reading it.


Just kidding. Thanks for the link.