[amowry]

Has anyone here had experience with these? Here's an example:

CNC Hollow Shaft 4th Axis Router Rotary Φ100mm 4 Jaw Chuck+MT2 65MM Tailstock | eBay

I'm thinking about getting one but replacing the stepper with a continuous-rotation variable speed motor to use it more like a lathe, up to around 1000 rpm. I'm curious about the quality of the bearings and whether they are suitable for this, or whether these are meant more just for indexing.

Many thanks!

[handlewanker]

Hi, most faults I have read about the cheap Chinese belt drive type 4th axes are in the stepper drive that is as weak as a kitten.

I doubt that the 4th axis types on EBAY have angular contact or taper roller bearing with preload capabilities, probably only deep groove radial types, so if you do a lot of fast revolving with axial loading you'll get some bearing wear and end movement that cannot be corrected.

You could rebuild one with better bearings and a stronger stepper motor, but it'll cost you almost double.
Ian.

[amowry]

Okay, I suspected that might be the case. Thanks for your time!