Question about linear bearings

I'm looking to make a desktop fixed gantry machine with a working envelope of 12" x 12" and maybe 4" in the Z. I'll be doing mostly wood/plastic but will probably occasionally mill some PCBs and some light aluminum work too. I see on the bay that there are kits that come with sbr16 rails and 1605 ballscrews for all three axis and all the extras. The price on these are pretty attractive and it seems they will make putting a machine together pretty straight forward. And yeah I know they aren't going to be 0.001" accurate over the length of their run. I'm just curious how the linear rails will hold up to saw dust... and the ballscrews too I suppose. Any maintenance issued vs the acme drive stuff or the skate bearing linear bearings?

Those chinese linear bearings and ballscrews are actually pretty good, I have seen many very good machines built with them. At the size you are speaking of building I doubt you would have any huge problems with accuracy or strength. As far as dust, try to design the machine as much as possible to keep dust of the moving parts. And have either a good dust shield system, or even better a dust collector of some sort to keep the dust under control.

I have been running my machine for over 3 years now with SBR16 and SBR20 supported linear rails with no problems. I cut MDF with a Vac head 3 times a week. The rails are the least of your worries.

Thats great to hear, as I have just purchased (and recieved) a set of Chinese 16mm supported rails, 1605 screws , bearings and couplings. Shipping was fast and well packed.
Im in the process of building a new machine from these components so to hear other good reports about them is reassuring.
I have noticed that some of the rail bearing blocks feel a little gritty as tho they may have some dirt/swarf in them. Im thinking of flushing them with WD40 or similar and then relubricating them. Any suggestions on the lubricant I should use?

cutting aluminum, the square rails are better..

but.. the supported roundrails also work for..

the grease on the rail is ugly, however wash it off only when you get there..
I mean after they mounted and ready to assembly the machine.. it simply protect against rust.. tough they are hard chromed..

I saw the wd40 has a type ""dry lube"" you might try that
Amazon.com: WD-40 300052 Specialist Dirt and Dust Resistant Dry Lube PTFE Spray, 10 oz. (Pack of 1): Industrial & Scientific

I scrubbed the bearings in alcohol and dried with compressed air. Massage in some grease into the C bearing and install on the rail. Clean the rail too. Dont lube the rail as the wiper on the bearing will just push it all around. The lube that you put into the bearing during the massage will be enough untill the next interval of maintenance you plan. In which you need to repeat these steps over again.(assuming there are no grease nipples-my sbr bearings didnt have any.