THK blocks and rails

[lgalla]

I have purchased various used THK blocks and rails on E-Bay and been worried if they are toast.I have THK-21 and THK-27'S smooth as silk.They move under their own weight.I purchased 3,THK HSR20R2CIME 44"rails and blocks NIB and they are very tight and actually feel like they bump and grind.
Possibly they have a heavy pre-load?Any how I suppose it is difficult to determine if your used blocks are good by how they feel.
I just went back to slide the blocks and wow you would swear they are toast.
Larry

[ksanalytical]

Larry,

I have several barely used THK rails and bought brand new truck direct from THK. None of them move under their own weight. They're pretty smooth other than that though. These are mild preload trucks. Very easy to slide on the end of the rail. I'd worry more about the loose ones.

Ken

[The Blight]

I have 2 THK SNS45 rails with trucks, and it takes a fair amount of force to move them, but these are heavy preload trucks, so that might explain it, but I don't feel any bumping or grinding in these. Are these caged ball trucks? Can you remove them from the rail without losing the balls?