Heavy Duty Lead Screw

I am looking forward to the answer from someone who knows - but as an ex design engineer in a related field I am thinking that a fancy linear ball nut device will last longest, more classically one would use bronze but would need lubrication (perhaps powder metallurgy impregnated with graphite would help here) and that there must be some of the graphite or molybdenum impregnated plastics/composites that are suitable. I did use the latter in a sliding bearing (cross shift on a fork lift) about 30 years ago.

thanks for your reply.

I already enquire about Graphally, but they said it may not be suitabel for screw application.

What do you think about Ampco 18 (Bronz)?

I am also trying for some composite material. If you have some info please pass on.

Thnaks.

Try this site: http://www.pfaffgroup.com/

They have extensive knowledge base in their catalogs based on bronze nuts.

basically there are 2 types of lead screw nuts: bronze and plastic. the reason is that the nut material should be softer then the screw material - it's easier to replace the nut then the whole screw if somthing happens... the plastic nut needs no lubrication in most cases and is more efficient in power transmission (about 10% more) - the downside is of course smaller load carrying capacity.

I suggest you check out a steel screw with an acme thread (unless the load is in only one direction) and a nut made of lubricant loaded Vespel (Dupont). The details will depend on the operating environment such as atmosphere, water, corrosion, contaminants, etc.

On a test fixture that was loaded, exposed to environmental chamber testing (-40C - 150C, four cycles of three hours per cycle) and then unloaded and reloaded continuously, we had the securing threaded pins and nuts (3/4") made out of 17-4 PH stainless (heat treated (prescription hardened)after machining). It machines like normal stainless but once heat treated, it wears like tool steel.