I ordered a set of these for a custom project. I slipped each one on to my new polished 8mm rod to try them out. The first one moved fairly freely, but I could feel vibration that suggested a certain roughness. I was hopeful that this was the clunker in the batch but it turned out to be the best of them all.
I bought some dry teflon spray lube made by Blaster (Lowes) and repeatedly sprayed the ball bearings, slipped them onto the rod, and ran them back and forth. A blackish lubricant began to appear on the rod, so I wiped it off and repeated this process until only white teflon lube was visible. They ran noticeably more smoothly and easily, but still not super smooth by any means.
I'm using two in my immediate linear motion experiment, with one moving more freely than the other. I'm still assembling the test stand, so we'll know in a few days how they perform. I think they will move smoothly enough to work, and hopefully they'll get smoother with use.
One other issue is that while the mounting holes are threaded, they are not threaded all the way through. So if you have a specific application where you only need to engage the threads, say 1/4" you are all set. But beyond that your screws will bottom. Also, in the q&a there was an answer calling the threads as a metric size M4X8. It took me forever to figure out that the 8 refers to the length of a screw, 8 mm. In this case I'm going to guess that is the depth of the threads. Using a screw in the hardware store, I ascertained the thread to be M4 .70. I ended up drilling through the mounting holes and using 6-32 hardware.
I'm giving them four stars as I think they are a great value for the price. But if I were building a production product, I would explore higher quality sources for similar bearings (if they even exist) as these are not as low friction and low vibration as I was hoping. Cautiously recommended.
- Amazon Business : For business-only pricing, quantity discounts and FREE Shipping. Register a free business account
