NSK Rails - Replacement balls and spacers?

[Lionclaw]

I just bought a set of used NSK H20 rails. One of the bearings is missing some of the balls and some of the little plastic spacers between the balls. The balls are 0.155" or 3.94mm in diameter. I could buy 5/32" balls from McMaster I suppose. Would the size be ok? Do I really need to use the little plastic spacers?

Anyone have any ideas? I'd be interested in finding more carriages too if someone knows where to get them.

[runinbymdnt]

I have NSK car and rail issues too. I have 12 - LY 20 cars and need longer rails. I am interested in seeing the response to your questions. A couple of my cars are missing balls. The guy that gave them to me said he had some more balls. I dont have plastic spacers between the balls. Are you sure they are suppose to be there?

[jstern429]

I have worked very little with that type of rail and car, but I did have a few of them and one was missing a few balls. I go lucky and had some from an old RC car so it wasnt a problem. How many of the balls did you measure? I would say if the one you measured was .155 and a 5/32 is .156 I would give it a shot. Also you stated that the trucks were used and the .155 measurment you got may just be smaller from wear. None of the trucks I have seen have had any type of spacers in them so I would say you dont need them. It may of been a cheeper truck seeing it had spacers and not a full set of balls. Jeff

[mrjab]

If you check the size with a micrometer (most are metric) you can find bearing balls on Ebay.

[fam891]

Hi Lionclaw. I work for the INA Bearing company (a competitor to NSK), and we come across this sort of thing quite a bit (where someone has a carriage that has a few lost balls). Unfortunately, you can't just stick any kind of ball in there. Although NSK might be slightly different, after each carriage (car) is machined, it is measured to see what the internal dimensions are. This allows the manufacturer to select the proper size of ball sort to put in the carriage. What is a ball sort? When the balls are manufactured, there are slight differences in the diameter of each ball. As a result, they are sorted into ranges depicting this difference. For example, if the nominal diameter was supposed to be 2.0000mm, you might have sorts like 1.9998-2.0000, 2.0000-2.0002, 2.0002-2.0004, etc. Once you know how loose or tight the carriage was machined with respect to the drawing, you can select the proper ball sort to ensure proper running accuracy and preload on the rails.

Unfortunately, you cannot just stick in any size of ball. It might work for you, but you run the risk of destroying not only the carriages, but the rails as well. Your chances of buying balls that all fall within the spec of the required ball sort is very low. The cost of buying a replacement carriage (or carriages) is far less than having to replace all of your rails and the other carriages (likely to be damaged from running over the damaged spots on the rail once it is damaged). I would not recommend that you buy balls from anywhere and stick them in the carriage (unless NSK measures the carriage for you at their factory and provides the proper ball to you). You might as well buy a new carriage.

As far as the spacers go, they are likely similar to our Quad-Spacers. Our Quad-spacer is used to separate the balls to reduce audible noise, as well as increase the smoothness of running. This is especially important on high precision laser machines. I have included a few links below so you can have a look at ours and determine if the NSK spacers look similar or not. They aren't essential to the operation of the carriage if you don't require the added features.

Brochure on Quad-Spacer (see page 2 for picture):
http://159.51.238.62/remotemedien/me...ai91_de_en.pdf

Dimensional information for size 20:
http://medias.ina.de/medias/en!hp.ds...ern=kuve20b-kt

I hope this helps.

Frank