What is this ball screw drive?

[josh591]

Anyone know what the following ball screw drive is called? It's a ball bearing screw but there's no ball bearing it seems. It's just a two pieces of plastic with a spring on it.

Is that separation in the middle normal or do you think I should turn it with some vice grips to close up that gap? It doesn't seem that I can tighten it easily because it's keyed so turns both the top and bottom unit. Seems like the spring is taking up any backlash.

Anyone seen this before? Thanks.

[CarveOne]

I haven't seen one just like that before, but if it doesn't have balls inside it should have a shape that conforms to the ball races in the screw. The spring forces the two halves to stay in contact with the sides of the ball race to eliminate backlash. It works just like the anti backlash nuts sold by DumpsterCNC for acme screws. You probably can't reposition it on the screw to close up the gap anyway. It needs to have a small gap for it to work properly.

CarveOne

[Kipper]

Yup I've seen a few of those. Not a ballscrew...it's a leadscrew....with ab provided by the spring....looks normal to me.

[johnmac]

That lead nut is correct, don't change anything. It is not a ball nut. It is threaded to match the screw. It is a split unit and the spring eliminates backlash.

John