THK Slide pack FBW? Cheaper linear system?

[InspirationTool]

So I was poking around THK's site, and I see this:

http://www.thk.com/technical/download/f.html#3

It looks to be a precision ball bearing "drawer slide" with max clearance of .1 mm (.004")

They are billed as "low cost" as compared to the linear rail stuff.

Sounds like it would be just the thing for a CNC router... Is there a reason I've never seen this in all the pictures of home build CNC machines?

Thanks!

-Jeff

[mxtras]

I designed and built an assembly machine (actually an elaborate fixture) for Rockwell about 8 years ago using these. I was not blown away with the performace, but it was adequate for it's purpose. The motion was a bit notchy - not as smooth as a linear bearing, of course, but I think it might be a reasonable option as long as you don't ask it to handle loads in two directions - use multiple sets to eliminate vertical loads on the carriage. In other words, if you load the carriage straight down (perpendicular to the rail) it will dramatically increase the rolling resistance and stretch the rail open.

Personally - I wouldn't use them for a router.

Just my opinion....you know what they say about opinions.

Scott