TH42 leadscrew keyway?

[great white]

Something I’ve never quite understood is why the Atlas lathes have a keyway cut in the threads nearly the whole length of the leadscrew.

I get why the keyway is there on the LH side as the reversing gearbox gear keys to the leadscrew in order to drive it.

But why the whole length of the leadscrew?

Perhaps its meant to give chips somewhere to go so they have a place to drop off the threads and not get bound up in the halfnut assembly?

Kind of a pointless question I guess, its just always rattled around in my head as to why…

 

[Jim F]

To drive the longitudinal and cross feeds.

 

[great white]

To drive the longitudinal and cross feeds.

Hmm, I’ll have to look under the apron again. Makes sense though…

 

[benmychree]

Many small lathes and even some larger ones without a separate feed rod use a keyed leadscrew, notably South Bend.

 

[markba633csi]

On an Atlas it drives the cross feed only. On South Bend, Logan, Sheldon, etc. it can do both long and cross (separately)