Re: [CAD_CAM_EDM_DRO] Re: shafting question

> I'd agree with Jan about using the largest diameter rails that you
> can if they are to be end mount only.
>

I've abandoned that idea after reading the posts. The idea was strictly to
keep costs down, I had no other preference for using end-mounted rail.

> IMO, crossed roller bearing are overkill for most "home made" cnc
> machines. Do become familiar with what the thk type linear bearing
> are though. THK is a manufacturer, and will prob'ly be found with a
> web search. Thomson also sells similar competing products.
>

I've seen these before; I wasn't aware of their capabilities. I thought they
were a fairly low-end product that had a lot of slop. After further review,
it became apparent I was incorrect.

> Second, the cost of plain thomson shaft is not too bad. Epoxy
> mounting this rail to the supports will save significant dollars. The
> supports are also expensive, but ARE ground; so the cost is
> justified, IMO.

That's a great idea! I never even considered that before. Thanks.

> P.S. The pacific bearings are a good product with some "caveats"
> (buyer beware): They require looser fits to the shaft (no pre
> loading here) than linear balls. This will mean that a bridge design
> is better than a gantry if these are going to be used. They are high
> speed/light load by design,

This would seem to go exactly opposite of what they claim on their website,
that their bearings have a greater contact area and thus are capable of
higher loads than ball bearings. Either way, I keep thinking that as they
wear they will quickly introduce a lot of slop into the action, more so than
a ball bearing.

Thanks again for the help & new ideas.
Rick