that's a separate issue - the belt pulleys aren't perfectly centered either. The bearings are tight though, and I don't think that any wobble from the pulleys transfers to the axle. After re-grinding, it was almost perfect.

It's true that this setup is not going to be nearly as rigid as a proper rotary table with worm drive or harmonic drive. But with those, it wouldn't be able to go to 1000 RPM for turning. The idea was to keep things simple and cheap and do mill-turn operations. In plastic it's perfectly fine, and I also did some small pieces in aluminium. In combination with HSM and a 24kRPM spindle, the cutting forces are not that big and it copes reasonably well. Just don't compare it to a Hermle or something ;)

Not sure, haven't tried yet. I've used it for aluminium and brass, and that works particularly well with my 24 kRPM high speed spindle (low tool pressure). In steel, the flex of the belt drive is probably too much, and steel likes lower cutting speed and higher tool pressure. Maybe small pieces of mild steel, with small cutters, might be ok, but it's certainly not going to hog into tool steel.

Could have, but I guess it would have been a lot more grinding (bigger surface, more material to remove). Maybe it wasn't too clear in the video, but before grinding there was a few 1/100s on the taper and the face of the mounting cone, and after grinding it was essentially perfect (no visible movement of the 1/100 indicator). So it worked well. I didn't film enough footage of showing the final run-out...

@@codemakeshare What was the final runout? Seems like with these cheap 4th axis and a AC servo you could build a pretty good rotary axis / CNC lathe. Thanks for the video, very interesting to a newbie!

no, unfortunately I don't... it's always very tricky to get any sort of documentation about AliExpress products.

it all came as a complete set from AliExpress (search for CNC 4th axis or similar - this is the NEMA34 version)

@@codemakeshare ohhh thank you so much ! Good job

yeah, good point. I previously bought hybrid closed loop stepper servos for my Opti CNC machine, and those came with a fairly good english manual. But the AC servo on the 4th axis only came with a printed chinese manual. A friend of mine found an english PDF of a similar drive, and using both, I managed to make sense of it. The parameters seemed to be all the same, just the wiring was slightly different. The performance however is really awesome, and it was very affordable for what it can do. It's been a while ago, but maybe I can dig it up some day and try to write up the most important settings.

@@codemakeshare It would be awesome if you could make a video about the servo setup. There are no videos on KZfaq that cover it.

@@codemakeshare Yes that will be really awesome. we are waiting patiently. kind regards from germany