[etech4]

I purchased a 12mm ball screw that had been machined down to 10mm for the bearing journal.
Because they only removed 2mm, the shoulder that the bearings butt up against goes only half
way round the ball screw! It's not machined deep enough to remove the ball grooves and get
a good shoulder all the way around.
Is this ok? Doesn't seem right to me.
I notice that NSK machines their 12mm ball screws to 8mm for the bearing journal and this gives a good shoulder.

Thanks
etech4

[assink]

No, that isnt good.
What u can do is turn down the screw to 8mm. Glue a bushing to the screw and machine this to 10mm with a shoulder

[CitizenOfDreams]

I would say, 10mm journals on a 12mm screw was a bad idea that should have been caught at the design stage. Is it too late to modify your project for 8mm ID bearings?

[mactec54]

I purchased a 12mm ball screw that had been machined down to 10mm for the bearing journal.
Because they only removed 2mm, the shoulder that the bearings butt up against goes only half
way round the ball screw! It's not machined deep enough to remove the ball grooves and get
a good shoulder all the way around.
Is this ok? Doesn't seem right to me.
I notice that NSK machines their 12mm ball screws to 8mm for the bearing journal and this gives a good shoulder.

It's always a good idea to have as big a journal as possible, all you have to do is you make a small spacer that is a tight fit on the shaft/journal that pushes hard up to the screw shoulder, this will solve your problem, don't have it turned down to 8mm that's a bad idea, these photo's will show you what needs to be done

[etech4]

Great ideas! Thanks, guys.
I was thinking about shrink fitting a spacer but Loctite may be a better idea. I will have to turn down the screw for the length of the spacer so I can true up the shoulder while it's in the lathe. Maybe 1/2" long spacer so it will have enough surface to glue tightly to the screw?
I don't want to turn down the 10mm section if I can help it because it has a threaded section that I may not be able to do a good job threading it back! The 10mm bearing journal is actually .001 inch smaller than 10mm. A 10mm bore bearing will slide easily on it. Should I turn the screw down anyway and bush it so the bearings have a closer fit?
I could only find two 8mm angular contact bearings and one 9mm, but found a bunch of 10mm ones so I want to stick with 10mm if possible.
This is to cnc the cross slide on a 7x10 minilathe so it doesn't have to be super strong but I want it to have as small backlash as I can make it on a budget.

Thanks again, cnczone is a great place! I would be lost without it.
etech4

[mactec54]

Great ideas! Thanks, guys.
I was thinking about shrink fitting a spacer but Loctite may be a better idea. I will have to turn down the screw for the length of the spacer so I can true up the shoulder while it's in the lathe. Maybe 1/2" long spacer so it will have enough surface to glue tightly to the screw?
I don't want to turn down the 10mm section if I can help it because it has a threaded section that I may not be able to do a good job threading it back! The 10mm bearing journal is actually .001 inch smaller than 10mm. A 10mm bore bearing will slide easily on it. Should I turn the screw down anyway and bush it so the bearings have a closer fit?
I could only find two 8mm angular contact bearings and one 9mm, but found a bunch of 10mm ones so I want to stick with 10mm if possible.
This is to cnc the cross slide on a 7x10 minilathe so it doesn't have to be super strong but I want it to have as small backlash as I can make it on a budget.

Thanks again, cnczone is a great place! I would be lost without it.
etech4

If the Bearings just slide on you should be fine, the nut is there to lock them tight to the shaft, design the spacer to suit the Bearing Housing, the spacer if done right is also used for a seal to run on

[etech4]

If the Bearings just slide on you should be fine, the nut is there to lock them tight to the shaft, design the spacer to suit the Bearing Housing, the spacer if done right is also used for a seal to run on

Sounds good! That's what I'll do. Thanks for the tip about the seal-spacer idea also.

Etech4