Why Threaded Spindle Bore?

[chips&more]

If I understand your question there are threads on the back end of your spindle. Some lathes with high speed can whip small diameter material until it bends. Be there and had it happen before I could stop it. So some will make stock tubes the thread on to support such material. Some of the larger spindle bore diameter lathes will have a three jaw chuck mounted on the end to support heavier material. I hope this helps

Yeah, happened to me too…once. And once is enough! My lathe is about 1,500 lbs and it was hopping on the floor when it happened. Lucky no damage done just had to go change my underwear.

 

[Wreck™Wreck]

A tool manufacturer may do whatever they want as regards design, if they went through the added operations and associated costs of threading the ID on the back of a lathe spindle there is a very good reason for doing so.

 

[chi JBS]

If I understand your question there are threads on the back end of your spindle. Some lathes with high speed can whip small diameter material until it bends. Be there and had it happen before I could stop it. So some will make stock tubes the thread on to support such material. Some of the larger spindle bore diameter lathes will have a three jaw chuck mounted on the end to support heavier material. I hope this helps

grin, before I knew what I was doing, I turned a perfectly straight 1/2" dia rod into a perfect "j". So it isn't just small dia stuff.