Screws for UHMW

[RJD2]

I have never used UHMW before, and was wondering what type of screws (wood, self-tapping) would work best to ultimately screw one 3/4" thick piece to another in a 90 degree configuration? Thanks.

Ron

[Uncle Cracker]

UHMW can be a bugger. I have used Plastite screws with some success. They are self-threading, and made specifically for plastic. To be honest, I see little difference between these and standard course threaded metal screws, other than the Plastites have a blunt tip. The ones I have I bought from a local plastics supply house which has since gone out of business. Make sure you drill the appropriate-sized hole, or the screw will swell the workpiece.

[jking]

Would you consider the application to be a permanent joint? If so, you might consider using a bed bolt type of configuration. You could countersink for a flat head machine bolt on the face & drill a hole with a forstner bit or cut a mortise for a nut on the mating piece. What type of material thickness are you using?

[phi1l]

You could also try pocket Screws using the coarse thread recommended for plywood or composite, but you would have to extend the pilot hole into the second piece of material.

I think you can also heat weld that stuff.

[LinuxRandal]

Machine screws work well if you tap the UHMW. If your going to be taking the item apart quite a bit, you might consider threaded inserts instead. Several parts of my Eurekazone (EZ Smart) system, are UHMW (primary components).

[RodKirby]

Machine screws work well if you tap the UHMW. If your going to be taking the item apart quite a bit, you might consider threaded inserts instead...

Ditto

I have drilled/tapped "many" 1/4-20 holes in 3/4" UHMW -and- in 3/8" UHMW sled runners. Works well.

[RJD2]

Thanks for all the information. I countersunk metal screws to make the connection, and drilled the holes longer than the screws. However, the pieces have a slight consistent gap between them that doesn't want to come together. Any suggestions?

Ron

[Brian G]

I venture a guess that the exit hole and entrance hole of the mating surfaces deformed slightly when you screwed them together.

Try slightly countersinking the exit hole and entrance hole of the mating surfaces. This will remove any "pimples" that may be causing the gap.

That's what first came to mind.

[RodKirby]

I venture a guess that the exit hole and entrance hole of the mating surfaces deformed slightly when you screwed them together.

Try slightly countersinking the exit hole and entrance hole of the mating surfaces. This will remove any "pimples" that may be causing the gap.

That's what first came to mind.

Absolutely!

I always C/S the exit hole - in any material - SOP

[Uncle Cracker]

I always C/S the exit hole - in any material - SOP

I'll bet it hurt when you did that on your thumb...

[RodKirby]

I'll bet it hurt when you did that on your thumb...

Very true

And on that topic - Sensitivity has gone, very little I can't do now - barely notice it

[iceman61]

Would you consider the application to be a permanent joint? If so, you might consider using a bed bolt type of configuration. You could countersink for a flat head machine bolt on the face & drill a hole with a forstner bit or cut a mortise for a nut on the mating piece. What type of material thickness are you using?

This is what I the last time I worked with UHMW, but I was attaching it to channel iron. Should work the same with UHMW to UHMW. That stuff is very durable.