Best anti friction additive for epoxy - (for mill leadscrew nuts)

[tabletop]

I would like some suggestions on a good anti friction additive to epoxy. I will replace my hobby mill's brass leadscrew nut with a 'cast in place' nut directly on the leadscrew. This is not a new idea. It is a very effective easy way to virtually eliminate backlash.
I've read that graphite powder is good but can be hard and therefore may cause wearing. Molybdenum is better but hard to find. Fine aluminium oxide can be good too.

Interested in info regarding additives, suggested epoxy/additive ratios and hopefully suppliers too!

Many thanks.

 

[MikeHalloran]

I've used molybdenum disulphide powder/paste in high duty cycle applications, and found that it is a very effective abrasive. I wouldn't use it on a leadscrew.

How about a split nut made of Teflon, with a pinch bolt?

Or a brass nut, and a brass locknut, locked together by an axial setscrew?

Or a brass housing like a plug valve body, filled with Teflon? You can tap the Teflon if you like, or just leave a clearance hole. Put a threaded plug in the open end, and use a big wrench on it to compress the Teflon. It's amazing how much you can distort the stuff, plastically.



Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

I would look at both the Al and Bronze filled epoxies. Here is just one of several companies that offer the combination. Al filled is commonly used for temporary tooling.

I would look to use BN (Boron Nitride Powder) as a lubricant. Another possibility is Colloidal or Micronized Graphite.

http://www.devcon.com/devconcatsolution.cfm?catid=34

Backlash:
My father once worked on a machine similar to a ruling engine where the lead nut was a leather pad clamped around the screw. He told me that this evened out any imperfection of the lead screw and eliminated backlash.

 

[Demon3]

The aluminium oxide you mentioned is amazingly abrasive, Moh hardness of 9, in fact it is used to make abrasives.

You could add fine PTFE powder (as already mentioned) or add a fluoroepoxy that polymerises in. These must exist as I have seen them used for anti-graffiti paints. Adding some kind of silicone should also work. You can get the PTFE powder in an aerosol spray can from RS Components for example to try it out.


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[patprimmer]

A grade of PTFE that fibrilates on shear would be best.

ICI used to make a grade called Fluon L169. I have no idea if it is available now.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[tabletop]

Ok, I have ruled out metals and other hard substances in favour of polymers since there appear to be many well suited that are less abrasive. What do you think about this stuff by dupont?

http://www2.dupont.com/Teflon_Industrial/en_US/products/product_by_name/zonyl_ptfe/zonyl_prod.html

Could be same but in small quantities....

http://www2.dupont.com/Teflon_Industrial/en_US/products/product_by_name/zonyl_ptfe/zonyl_prod.html

....getting interesting.

 

[patprimmer]

I think the Zonyl MP1300 is the equilivilent to the Fluon L169.

If so I think it should work at about 10 to 20% add rate.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.