[Wallybanger]

I just bought a bunch of chinese ballscrews/nuts from Linearmotion and I am going to need to turn one of the ballnuts down to mount bearings on it. The body of the ballnut is apparently 28mm (I haven't received them yet) and I'm going to need to turn it down to 25mm. is there 1.5mm worth of meat that can be removed from the ballnut body? If not, I'm going to need to formulate a new plan.

[Timbob]

Build a 30mm od x 28mm id sleeve. You're asking for trouble machining it down.

[Christian Knüll]

Hi,

the nut itself is made from hardened steel - you can only grind it.
Turning is not possible unless it is already mounted in a soft sleeve.

However - the outer diameter is usually precision ground - if you use 28mm bearings and add a stop ring to the nut you may already have what you want.

Christian

[cyclestart]

Wild guess here, you're having difficulty finding AC bearings @ 28mm id.
I've considered building a rotating ballnut by the sleeve method mentioned but the assembly sketched up kind of bulky. You'll need a method to preload the bearings but you're probably already aware of that.

[pupfield]

I got mine from them turned with bearings installed.

You will need to anneal the ends before you can turn it and then harden it again. Good luck with that. If you do, turning it down to a size that will fit a standard sleeve would be your best bet.

[Wallybanger]

Wild guess here, you're having difficulty finding AC bearings @ 28mm id.
I've considered building a rotating ballnut by the sleeve method mentioned but the assembly sketched up kind of bulky. You'll need a method to preload the bearings but you're probably already aware of that.

Exactly. I can find 30mm, 25mm but no 28mm, which is ridiculous because I can get 28mm tapered roller bearings but, of course, they are WAY too thick.

A 1mm thick sleeve may be my only option but I bet that it's gonna be a PITA to machine.

[bhurts]

I didn't see in your posts the actual diameter od the screw but I do have a solution that may help you by allowing you to choose a bearing size that is available to you. It will also work with 2 ac bearings or 1 radial bearing and two thrust bearings. It would cost you 2-3 inches of screw travel but it works well. It would also most likely let you use a smaller I'd pulley. It's hard to describe but if you can bear with me till Friday or Saturday i'll post some picks.

Ben

[Wallybanger]

I didn't see in your posts the actual diameter od the screw but I do have a solution that may help you by allowing you to choose a bearing size that is available to you. It will also work with 2 ac bearings or 1 radial bearing and two thrust bearings. It would cost you 2-3 inches of screw travel but it works well. It would also most likely let you use a smaller I'd pulley. It's hard to describe but if you can bear with me till Friday or Saturday i'll post some picks.

Ben

Hey Ben,

I'm using 16mm ballscrews and the area I have to work with on the ballnut is 28mmOD x 32mm (1.25"). I'm getting a quote on some 30x47x9 mm AC bearings from NSK. I'm keen to see what you've come up with, post some pics when ya got em

Cheers,

[Timbob]

I didn't see in your posts the actual diameter od the screw but I do have a solution that may help you by allowing you to choose a bearing size that is available to you. It will also work with 2 ac bearings or 1 radial bearing and two thrust bearings. It would cost you 2-3 inches of screw travel but it works well. It would also most likely let you use a smaller I'd pulley. It's hard to describe but if you can bear with me till Friday or Saturday i'll post some picks.

Ben

Make the sleeve oversize, fit on the ballnut, then turn to size. Make it longer so you don't have to turn it around, then part off the excess.

[bhurts]

Ok I hope this makes since. The parts you would have to make are green. Everything is labeled in the first pic. If you have any questions I'll do my best to answer.

[Wallybanger]

Yep, that's pretty much exactly what I came up with except I'm going to use larger bearings and run the ballnut on the inside of the bearing sleeve with the pulley on the bottom. I was thinking about the possibility of a wave spring washer and a c-clip instead of the nut but if I can get my buddy to cut the threads for me I can probably find a nut to fit.