lead screw diameter and pitch

[alan knightParticipant @alanknight67321]

Desiging a machine to copy carvings, and Im looking to make it automatic, I have designed a rolling carrage that sits on 2 50mm diameter mild steel bars 2400mm long I was looking to install a lead screw along the side and the power the traverse with a small electric motor and a variable speed control, For a 2400mm length whats the recommended dia to allow the screw to work without diflection and is there a recommended pitch for the leadscrew I was looking for a feed of around 1-5mm a minute. Am i better using a fine lead screw pitch and running the motor slightly faster of am I better using a coarser pitch and stepping the motor down by gearing it?

[alan knightParticipant @alanknight67321]

[BazyleParticipant @bazyle]

Alan,

I think the support bars may already be sagging under their own weight apart from the difficulty in moving them. The leadscrew would be similar plus difficult/dexpensive. I would suggest tubes for the carriage support and looking at tensioned wire or toothed belt for the traverse. Winding the wire around a drum converts length into angular movement and a gear train.

One of the factors in leadscrews is the thread angle. Big lathes have quite course treads eg 4tpi but on a 1.5 to 2 in dia rod. A small lathe might be 8 tpi on a 3/4 in dia. That might give you some idea.

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