[Kotyara]

Hi folks,

Got a line on some surplus Bosch linear rails for a very good price and would like to use them to build a router mainly for aluminum cutting. The only problem is the blocks have zero preload and as far as I understand it is not adjustable. Would that be a problem in a CNC application?
Here's the spec sheet: http://www13.boschrexroth-us.com/got..._ball_rail.pdf
Part number is R162289423 (it's on the second page).

Cheers,
Alex.

[crazydiamond]

In short yes... You'd typically like to see light to medium preloads for routers.. But if you intend to machine aluminum I'd recommend a medium preload (see https://tech.thk.com/en/products/pdf/en_a01_068.pdf)

That being said, you can switch out the balls in the blocks to achieve higher preload. It usually entails a bit of trial and error, but replacing the existing 0 preloaded ball with something 3 tenths larger (0.0003") should work (see http://www.cnczone.com/forums/vertic...tormach-7.html see post 55-67)

The first challenge is accurately measuring the sizes of the balls you're taking out.. Manufacturers are very secretive about these specs.. A good micrometer should get you pretty close though..

Also, for what it's worth, I've got a set of THK HSR15's with medium preload, and they can support their own weight with the rail held vertically (with bearing wipers removed, so it's just friction/preload holding)..

Cheers, Devin

[Kotyara]

Thanks Devin! You've confirmed my fears. I'll have to pass on these unfortunately, don't really want to fiddle with the insides of German-made bearings, they're not known for being tolerant to rule breaking Too bad, they're basically the same price as HIWIN 15mm.

[crazydiamond]

Ha! You wouldn't happen to be talking about a certain ad up in Guelph Ontario, would you?

[Kotyara]

Yes, that's the one. Is it famous here?

Edit: Actually, since you're in Canada, do you know of any good sources of reasonably-priced CNC parts in Canada (rails, motors, screws, etc.)? Best I could find are a couple US-based stores selling Chinese stuff, but with the customs/taxes it's cheaper to get it directly from China...
Edit 2: Nevermind, found this thread: http://www.cnczone.com/forums/canadi...-software.html