Re: tapered roller option or several reasons for NOT using tapers as a ball screw support bearing.
1. friction
2. package size
3. axial runout
Some of the taper axial capacity comes from rolling resistance of the tapered rollers. BUT some also comes from sliding friction of the roller sides against the flanges. Common trick in racing axles is to replace tapers with A/C balls - reason, to reduce fricion albeit at a loss in fatigue life due to lower capacity.
To get ZERO to negative axial clearance with a preload in a taper, you WILL have more rotating torque that with a preloaded ball. In my case the OEM ball bearings (modified 6204s) had something like 75lb preload. We replace them with 480 lb preload A/C true ball screw bearings. The A/C bearings take LESS torq to turn the handles than the OEM's.
Although you might find a taper that will fit (ID and OD) in place of the ball type, the axial width is probably gonna be wider - getting two with comparable radial runouts is gonna be even tougher. They may tend to radially "fight" each other when packaged in DB mode.
Yes, you can mess with different bearing retainers and other mods to fit T/R's in place of the balls but compare that to a "bolt in" ball bearing DESIGNED to do what you want/need to do. No comparision.
You are looking for minimal AXIAL RUNOUT in a ball screw bearing. Most tapers are NOT machine tool grade. Since radial runout of a taper does affect axial runout, it is another issue to have to deal with. Yes, there are M/T grade T/R bearings but they are not easy to find.
When you add up all the compromises, it doesn't make sense (to me) do do anything but install ball screw bearings.
NOTE: having been involved w/ball bearing engineering for a number of years, I know more tricks than the average bear about how to cheat up and use bearings in unique ways.
When it came to trying to tune up my BPT/Eztrak, I simply bit the bullet (teeth still hurt) and bought the proper bearings.
When you buy the best, you are seldom disappointed.  |