Re: Linear bearing types?

Poured lead or type-metal bearings are still used extensively on some
older-type industrial machinery and they are very successful - hence
there are machines around here still running with them which are over a
hundred years old. One particular machine I can think of is a
file-cutting machine where the leadscrew nut is actually a split brass
block hollowed out to form a permanently in-situ mould which is filled
with lead. In production work, where the machine is subject to
continuous severe vibration as the chisel strikes the steel file blank,
these cast bearings last several weeks before needing re-casting which
is then a simple matter of cutting off the old lead and remelting and
re-pouring it - about 5 minutes work and you again have a precision
fitting new feed nut. While there obviously would be some wear over a
period of time I don't think this should be a problem as, whenever you
want to do a really precise job, you can just cast a new nut before
starting. It also has the advantage that, if you set the carriage
position before casting, you shouldn't have to readjust the machine for
screw rotation on the new nut. If you use lead, it is also somewhat self
lubricating - if you can still get lead that is, in this age of terror
over using anything useful!

Jon Elson wrote:

>
> > Anyway, what I'm wondering about is maybe pouring linear bearings
> > around semi precision shafting. I've thought about babbit, and just
> > heard about this stuff called Moglice. Any ideas?
>
> Well, the puored bearings would wear quickly, and it doesn't sound
> like there would be a way to adjust play. but, flex in the shafting
> would make it a very inaccurate machine.

Best wishes

Ian

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Ian W. Wright LBHI
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