Sooooo I got these lil fellers today..
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Sooooo I got these lil fellers today..
Hey i only skimmed through your thread, dont really have time to read all the replies, i suggest for framing to go with RHS it is reasonably priced, i would then epoxy granite fill the frame for improved damping and strength.
as for linear rails i have had great success building small machines with what some would consider "overkill sized rails" 15mm HGR style rails will serve you well, but you need to consider butting the rail up to a reference edge and using either grub screw or wedge style system to press the reference side rail against the reference edge, the other rail on the same axis will be "floated in" so to speak. If you just bolt a 15mm HGR rail down on a precision ground or machined surface and dial indicate it straight, you will have alignment issues later down the track when milling steels, because without a referene edge and grub screw tension the rails cannot handle very much lateral load, certainly not as much as they were designed to handle. also you need to think about potential crashes, which can easily destroy even the best alignment. So i suggest 30mm HGR rails against a reference edge, this will be plenty rigid and will handle machine crashes well. The reference edge technique is an industry standard, many diy machines dont use it probably because of lack of access to machine shops. check out my crowdfunding campaign for some inspiration, i build highly accurate desktop sized machines and have just developed the latest called "Alius" https://www.kickstarter.com/projects...?ref=user_menu
Also some of the chinese HGR linear rails and blocks are very good quality, dont fall into this "its chinese crap" pit. Plenty of good gear comes out of china, the reliability of the rail and blocks depend greatly on rail alignment, cleanliness and lubrication if you take care of those factors the chinese rails will serve you well.