re:leadscrew bearings / machine design

Dennis wrote:<snip>A better design is to use two angular bearings,

>but the cost is considerably higher. Each bearing costing about
>12.50 each and two required per lead screw.

Hi all,

Radial bearings are much cheaper and CAN be used in thrust
applications. Typical THRUST rating is one-half the AXIAL rating.

Use 2 with shim washers (.001-.002 typ.) between to make a FIXED
style mount for a leadscrew. Both bearings in a common bore/housing.
A single radial bearing at the other end of the leadscrew for support
(if necessary).

2nd tip. Ask YOUR SUPPLIERS what is COMMON, before specifying a
bearing(or other part). You may find that the industrial supplier
near you has "stocked up" to supply some mfr. or provide replacement
parts very near to what you need. At greatly reduced cost. For
instance, a 10mm bore(.393) may be a much different cost(more or
less) than a 3/8(.375). Same for O.D., or thickness. You can probably
change the design to use either one, if you do it BEFORE you build
the part(s) you have designed.

Even the national suppliers, like Stock Drive and Grainger(Berry)
often have SIGNIFICANT price differences between nearly identical
parts. Same holds true for electronics.

Common sense really, but often overlooked by a do-it-yourself-er. Or
someone working from a plans set.(be sure to get approval from the
designer if you change the plans, though! He/ She may know something
you might be missing!)


Hope this helps.

Ballendo

P.S. Recently there have been a lot of questions re: Machine design.
And common practice(s).

IMO, the best way to find this info is to look at the solutions of
others. Dennis has a number of pics on his site, but don't stop
there... There are HUNDREDS of pictures(details and over views)on the
internet of cnc machines! Home-made and otherwise.

Also get the component part mfr. catalogs. Ballscrews, linear ways,
motors, etc. The wealth of info here is incredible.

Lastly, peruse the sales literature for the commercial machines.
Often they will attempt to distinguish themselves by listing and/or
explaining what special features or solutions they have found/used
for common problems. Even if their solution is out of your reach, the
description of the problem solved can be very helpful. And help you
know what to look for as you continue your learning...