Hi Guys,

I just received my first pair of Thomson linear rails and pillow block bearings. I just had a few questions for people familiar with them. They are Thomson Super Pillow Block bearings (SPB 12) and are in what appears to be excellent physical condition.

I expected the bearings to not have any skew movement while on the rod. The bearings I have do move a tiny bit... as in, they can be "twisted" a little back and forth. Am I explaining that right? I know they should slide back and forth and twist around the rod but they also seem to have a little built-in slop.

Is there a way to adjust the slack out of them or is this intended? Just being my normal freaky self.

Let me know.

Thanks!

Darren

I am familiar with Thomson TWN 16 which fit around 1" shaft and they do not have any slop. I also have undersize shaft with slop in it but I am afraid to use it for same reasons that you have. The shaft is hardened. It brought another question in my mind, how do I know when the bearings are worn? and the only answer that I can come up with is if there is too much slop. But your bearings are linear and maybe I am mixing apples and oranges, it would'nt be the first time.

Here is a pic of what I have. I'm hoping all is well with these, they are both Thomson rails and bearings so it shouldn't be undersized rails.

http://home.att.net/~fair451/ebay4/thomspb12_3_1.jpg

Most of the pillow block holders have a set screw for tightening the ball slide. Once it is tight you will find it will not spin as easy around the shaft.

Originally posted by HomeCNC
Most of the pillow block holders have a set screw for tightening the ball slide. Once it is tight you will find it will not spin as easy around the shaft.

There is a plug in a threaded hole on the side of each pillow block. I thought that might be what it was but once I removed the plug I don't see any set screws...just the threaded hole. I'll take another look tonight.

I am using the same rails and blocks for my project .... bought surplus.
My problem was a slight haze of rust on the rails and was going to ask for suggestions here, then decided to contact thomson tech support.
I received a reply very quickly
You might want to contact them for maintenance info for your bearings.

here is the reply I got concerning the rust: (and an email address)

Since the rust is not only on the surface but has penetrated into the surface, any cleaning up procedure will be suspect as small pits cause by the rusting can be nucleation sites for future premature failure.
You can try to remove the surface rust using any commercially available product such as Naval Jelly. You may need to use steel wool or other similar product to remove the rust.
After you have finished, you can protect the surface against futher rusting by coating it with a light machine oil. Any type wiil do as long as it completely covers the shaft surface to protect it.
Regards,

John C. Bandrowski
Chief Engineer
Danaher Motion
e-mail: John.Bandrowski@Danahermotion.com

the side hole is 1/8" pipe tread for grease fitting. Setscrews are found in open bearings like the ones that sit on top of the shaft. The ones I was refering to are like those shown except they are double in lenght, hence the name twin.

Darren, the bearings you have are "self-aligning" and designed to work in pairs. If you think of the rails as the X axis, then you should have a couple of degrees of radial movement about Z, and a whole lot of radial movement about X. If you take a plate and attach both bearings on one rail to two corners of the plate, then the radial movement about Z will vanish (like in the TWN blocks) because the bearings will have "self-aligned" themselves to each other. Attach the other two bearings to the other two corners of the plate and the radial movement about X vanishes (assuming the rails are attached to something).
I hope this helps.

Steve

Originally posted by steveald
Darren, the bearings you have are "self-aligning" and designed to work in pairs. If you think of the rails as the X axis, then you should have a couple of degrees of radial movement about Z, and a whole lot of radial movement about X. If you take a plate and attach both bearings on one rail to two corners of the plate, then the radial movement about Z will vanish (like in the TWN blocks) because the bearings will have "self-aligned" themselves to each other. Attach the other two bearings to the other two corners of the plate and the radial movement about X vanishes (assuming the rails are attached to something).
I hope this helps.

Steve

Bingo! I appreciate the very informed responses from all and i think you have nailed it Steve.

Thanks for the information. I'll have to find out the maintenance for these bearings. They are grease free right now.