[Lab] bearings for a 12x9" mini cnc machine $125

Darcy Whyte darcy at siteware.com
Fri Jun 3 00:31:38 EDT 2011

I just figured out that this should cost about 125.00 plus shipping for
bearings. It works out that 14mm linear bearings are the best deal for all
three axis. http://mambohead.com/2011/06/linear-bearings-for-small-cnc/

I think that's pretty affordable so for that size of a machine, there is no
sense fooling around with trying to use ball bearings like I did for my
laser project (which has a much larger cutting area). For that the linear
bearings are way more so the roller deal starts to make more sense. I think
this is why you start to see v-grove bearings and stuff for larger projects
since they can ride on cheaper supports.

My next question is what to use for leadscrews/ballscrews, ball bearings and
couplers for stepper motors?

I know a 1/4-20 rod is used on a makerbot. Would that be too flimsy for a
small cnc? If so, then what is a good answer (and supplier) for that?

Here's an odd question. Is it necessary to support the screw rod at the
stepper motor side with a ball bearing? Can somebody convince me that this
is necessary? The stepper already has bearings in it so it seems redundant.
And then the stepper could be solid coupled to the shaft.

Another oddball question. Let's say the 1/4-20 rod is too flimsy and I have
to get a "real" screw and nut. Can't it double as a support rail? So an axis
would just have one pair of linear bearings riding support rod at one end
and at the other it would ride a screw rod with two nuts (so there is 4
points of contact).
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