[Jay-D9]

Hello, hope someone can steer me in the right direction.

Replacing the ball bearings in a Star linear carriage, 4 units altogether. balls are 4.8mm/- 3/16; have no problem finding the size but how far up the quality ladder do I go? and can I use SS instead of the steel ones presently? Do they need to be a certain hardness?

As you might see in the second pic the difference in the balls, some where stuck in the back tube; had to drive them out with a drift punch, might as well change all the balls in all the bearing while I'm at it.

Thanks for any help you might have!! Cheers.

[peteeng]

Hi Jay - Use balls intended for bearings. Do not use SS ones as they are not as hard and will fatigue quickly. Buy the best you can afford. Balls are usually not dear. Plus since the cars and rails are used get the size ball above the nominal old ones. This will preload the carriage and if they are on a cnc mill or router will give better performance. Peter

[servtech]

Hello, hope someone can steer me in the right direction.

Replacing the ball bearings in a Star linear carriage, 4 units altogether. balls are 4.8mm/- 3/16; have no problem finding the size but how far up the quality ladder do I go? and can I use SS instead of the steel ones presently? Do they need to be a certain hardness?

As you might see in the second pic the difference in the balls, some where stuck in the back tube; had to drive them out with a drift punch, might as well change all the balls in all the bearing while I'm at it.

Thanks for any help you might have!! Cheers.

I would look into replacing the complete shoe set. They are manufactured to micron tolerances. You have no way of obtaining balls the optimum diameter for your shoes, particularly if you want accuracy and repeatability. 4.8mm balls can be obtained in a range of hardness and tolerances.

[mactec54]

Hello, hope someone can steer me in the right direction.

Replacing the ball bearings in a Star linear carriage, 4 units altogether. balls are 4.8mm/- 3/16; have no problem finding the size but how far up the quality ladder do I go? and can I use SS instead of the steel ones presently? Do they need to be a certain hardness?

As you might see in the second pic the difference in the balls, some where stuck in the back tube; had to drive them out with a drift punch, might as well change all the balls in all the bearing while I'm at it.

Thanks for any help you might have!! Cheers.

Yes, you can use 440 SS Balls, 4.8 diameter is not 3/16 you must use the correct size or .0001" bigger than the original always get the highest grade you can find whether it carbon steel or 440 SS.

Type 440-C steel balls are uniformly hardened and tempered throughout their entire diameter to achieve maximum strength and quality. Ball hardness is 58-65 Rockwell C as measured on parallel flat surfaces. Also, type 440-C stainless steel balls are magnetic.
Carbon: 0.95% to 1.10%
Chromium: 16.0% to 18.0%
Manganese: 1.0% maximum
Silicon: 1.0% maximum

440 grades of martensitic stainless steel are often used for load-bearing elements such as balls and guide rails because they have added carbon to improve hardness Each manufacturer has different offerings in terms of the grade of stainless steel used for each component of the linear motion system.

The 440 ss Balls run around the same hardness as carbon steel Balls

[David_Williams]

Your direction seems on track for replacing the ball bearings in the Star linear carriage. Consider the following factors when selecting replacement ball bearings.

Size: Ensure that the replacement balls are the correct size, which you've mentioned as 4.8mm or 3/16 inch.
Material: Using stainless steel (SS) balls instead of steel ones can be a good choice, especially if you're looking for corrosion resistance.
Hardness: The hardness of the ball bearings is indeed an important factor. Bearings typically have a Rockwell hardness value specified. The appropriate hardness depends on the specific application and the load that the linear carriage will be subjected to. For general purposes, a hardness in the range of 58-65 HRC (Rockwell C scale) is common. You may find the original specifications or consult with a consultant for guidance.

Considering the issues you've encountered, such as balls getting stuck in the back tube, it's a good idea to replace all the balls in all the bearings to ensure uniform performance and longevity. Make sure to clean the components thoroughly during the replacement process to avoid any debris affecting the new bearings.

If you have the original manufacturer's specifications for the linear carriage, that information could guide your choices for replacement materials and hardness. If not, you might contact the supplier for recommendations based on the application and operating conditions.