View Full Version : Grease in my THK bearings/carriages

10-07-2004, 05:07 PM
I have some THK bearings/carriages. They are medium size and large size (4", 6" long). When I bought them they were covered with what looked like Cosmoline. It is a very thick gooey type stuff that is tan and opaque.
When I put the bearing on the rails to test them the carriages moved slowly because of the grease. So now I'm removing that grease.

1. Is it possible I'm removing the kind of grease that is supposed to be on the bearings? (i.e. Not Cosmoline but bearing grease?)
2. What kind of grease do you use on your THK bearings?
3. How much grease is supposed to be in there?
4. It looks like there is a trough between the ball bearing races where grease can sit (Top part carriage between the races.) Is that space supposed to be filled with thick grease?

Any help appreciated.................Sam

10-07-2004, 05:18 PM
hmmm ... I've got some bearings like that too and have thought of putting in a "lighter grease. I'm not ready to use them yet so I've had that on the back burner. But, as you say, they sure do seem to fight movement..not very fluid at all.


10-07-2004, 05:34 PM
I run mine completely dry, but that's just me.

10-07-2004, 05:42 PM
hah! I guess you're saying.."whatever works fur ya". Have you checked for wear now and then? do they hold up pretty well without lub? I suppose the sawdust CAN act as a lubricant. :confused:

10-07-2004, 06:34 PM
I have come to the conclusion that I have removed the proper grease from 2 of my THK bearings. LOL. That is not Cosmoline (A rust preventative grease used in shipping, like what firearms come packed in.) I thought is was Cosmoline because the stuff was all over everything like it was shipped that way on purpose to prevent rust, not! So, clean the outside of your carriages and rails but don't remove the grease inside the carriage at all. That is good grease if it doesn't look dirty.

Besides adding some grease to the 2 carriages I "cleaned" I also want to be able to lightly wipe some clean grease now and then on the rails.

Recommended Grease:
1. AFA Grease (THK)
2. NBU15 (NOK Kl├╝ba)
3. Multemp (Kyodo Yushi)
or equivalent

Update: I just bought some THK AFA grease for $15 (including shipping) for 70 grams at the THK site. That's only about 3 Oz. If that isn't enough I'll start using bulk lithium based machine grease from Northern Tool at around $2 for 14 oz ( Lithium Grease at Northern (http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=6970&langId=-1&catalogId=4006970&PHOTOS=on&productId=200308741&categoryId=0) ,"Fits most grease guns. Ideal for lubricating and protecting bearings, cams and other sliding elements.")

10-07-2004, 09:19 PM
Our router at work doesn't use grease. It has oil lines into the carriages and is oiled automatically at fixed running time intervals. It uses a light to medium weight oil.

10-10-2004, 09:26 PM
I run em dry because I can't imagine the dust and grease "mixture" being a good thing. Without grease the dust doesn't stick. I have no idea if I am ruining the bearings, but since I am running at 10% of thier rated load, I am sure they will be fine. When I was a kid I used to clean the skate board bearings in gasoline. They were open ball bearings and they would run fine in the dirt as long as you did not oil them. If you oiled them they ran in a gritty soup.

I have not noticed any wear so far.


10-10-2004, 09:51 PM
On my machine it placarded "Lubricate weekly with General Purpose Lithium grease", having my own ideas about todays lubricants I use a synthetic lube but my guess is the added expense is unnecessary.

10-11-2004, 07:04 AM
I use a dry PTFE spray lubricant on mine. Dries quickly so the dust doesn't stick. I don't know if it's the best thing to do, but it's working so far. My machine prolly won't be used enough to worry about wear.

10-11-2004, 07:14 PM
The INA rep was just here, he says our recommendation of EP2 white lithium grease about once a week is good for sawdust. THK type bearings usually have very good wipers but if you don't use rail plugs you'll still get sawdust in the bearings. Greasing them regularly should purge contamination, just add grease until you see it squeezing out through the seals.

A note on synthetic grease- If you change back to regular grease be sure to clean out all of the synthetic or you'll probably end up with a chemical reaction and some stuff that doesn't look like grease anymore.

09-07-2006, 08:52 AM
Hi, Just bought som thk rails/bearings from ebay and was wondering where I can buy a cheap grease gun the fits the grease nipple
(HSR 35)


NC Cams
09-13-2006, 09:02 PM
Alvania #2 (Shell) is a common grease used in linear guides with rolling element balls. Sort of a milky/yellowish white grease.

A 'lighter' grease (cream colored) with less viscous drag can be had via the use of Beacon 325 (Exxon I think). Although it is rated as NLGI #2 it is a bit "runny" and is probably a NLGI 1-1.5 viscosity rating.

If you run them "dry", you will probably see more instances of wear, especially if you oscillate back and forth a lot. Skate bearings can be run dry as they are essentially "throw aways". You simply can't compare skate bearing use to linear guide use.

Synthetics: at room temp, these really don't buy you that much - especially at the price. These REALLY shine at high and low temps. For room temps, a typical non-synthetic is QUITE adequate.

Since debris contamination is the most common cause of grease failures (not temperatures which is where synthetics would help), the use of a reasonably priced mineral based grease is perfectly adequate, especially if you purge out the debris via regular regreasing.

However, running linear guides dry is not especially a wise thing to do.

09-15-2006, 09:59 AM
Hi nc cams,

thanks for letting me know which greases I can use, but wanted to know if their is any other option than using the very expensive thk grease gun to grease the bearings?


NC Cams
09-15-2006, 10:29 AM
I can't speak for Belgium but automotive "cartridge" style grease guns are NOT very expensive here in the USA. You can get them quite readily from the local automotive parts suppliers. And there are many 'chains' in the USA to choose from.

Depending on the supplier, finding single cartridges of the noted greases in the prior post may take some searching both here and/or in Belgium.

Essentially, if you can get clean, fresh grease to purge the debris out of the trolley, that's the important thing to do. Hence, pretty much any automotive EP rated chassis grease should suffice.

A hand pump "generic" grease gun will easily do just that probably for a fraction of the cost of a THK one - all it has to do is fit the zerk fitting. The last one I bought was under $15 USD as I recall.

The viscosity of automotive chassis greases might be a bit higher than what you need but that's less relevant than purging contaminated grease ouf of the system.

09-15-2006, 12:01 PM
what about filling the holes in the rails with silicone would that help keep the debris out of the bearings? if you needed to take the rail off for some reason just peel the silicone out or are the rail plugs cheap enough to do it the right way?

NC Cams
09-16-2006, 11:02 AM
Good idea TRUMAN.

Anything you can do to keep contamination out of the rails/trolleys would help the durability of the system.

Rail plugs may be "right" but they could more easily be pulled/dislodged unintentionally. The silicone would be tough to dig out (unless you used some release agent first) but it might be more robust.

07-04-2008, 08:46 AM
I have come to the conclusion that I have removed the proper grease from 2 of my THK bearings.

I have just tried using light machine oil as a first service (no lubrication instructions!) to discover the Y axis now has a shimmy as it gets toward home, wiping all the oil off seems to have improved the situation. After reading a lot of the posts, looks like the Lithium grease is gonna get a shot...
Any suggestions would be helpful? Plastic sign router :confused:

Matty Zee
07-06-2008, 11:44 PM
I have been running my homemade router for the last month or so on only the grease that was in the bearing (only ~2-hrs per week). I've recently bought some Shell Alvania #2 grease but i think i've let too must dust get into the bearings. I also bought some THK double seals kits for my blocks but they only just arrived.

Now i need to add the extra seals/wipers and grease up my blocks but i have a question. I didn't add the nipples onto my blocks when i assembled my router and i think the blocks may have dust in them as my dust extraction isn't finished yet. Should i clean my blocks when add the seals or do you think the purging will eventually clean the blocks out? what would i use to clean them? (SHS15 series)