how can I get uhmv perfectly flat

[Norm Dowsey]

Help! I have a piece of uhmv that I would like to attach to my rip fence but it is not perfectly flat. Any suggestions would be appreciated. Have thought about running it through my planner but I am not sure that would work. Anyone ever tried this? Thanks in advance.

[David Wong]

Great question. I bought a piece of UHMW and it had circular mill marks on the surface. I tried planing and scraping, with some success, but I could not stand the static-y plastic shavings all over the place. Hoping for a different way.

[scott spencer]

drum sander

[Kevin W Johnson]

I'm wondering if this is a common problem? I've been intending on facing my fence with UHMW. But if it's hard to get pieces that are true, I may do something else.

Will the piece you have not flatten out when you attach it to the fence? I haven't fiddled with this stuff in any size to know how it acts.

[pat warner]

That's it's nature, (cupping and twisting).
You can plane it , maybe abrasive plane it but don't expect eternal stress free flat life.
Slippery yes, machineable too but it does change shape. If flatness is paramount I'd look at other substrates.
The flatness and thickness specs on polyethylene stink.

[Larry Edgerton]

I make shaper fences out of UHMV. I run it through the planer with no problem, but I do have a SCM that I can slow down to 16fpm with a Tersa head. I plane one side and attach it to 1/8 or 1/4" aluminun backing plate. Its not ridgid enough to use alone even in 3/4" thickness. It will bend with the powerfeeder pushing on it and cause severe and sometimes scarry snipe, so it needs a backer of some kind.

Really didn't work out as good as I thought it would. Wears on long runs, too flimsy, but scary if a cutter catches it. I'll probably not use it again for that even though I have a ton of the stuff.

[Jim Foster]

What's UHMV?

[Jerry Bruette]

What's UHMV?

Should be UHMW...Ultra High Molecular Weight. Common term for the teflon, nylon, delrin etc. plastics used for fences.

[Carl Beckett]

Depending on thickness, this stuff is pretty flexible (and it creeps a fair bit)

So to get it flat involves fastening it to a flat surface..... (meaning by itself - its too flexible to worry about 'flat' because in use it wont remain. So my advice is to start with a constant thickness (drum sander? Or purchase it this way), and then pull it down against something 'flat'. I suppose you could fasten it first and then machine flat (again, drum sander).

Its funky stuff to machine - likes to stretch out as the cut finishes, etc.

[ian maybury]

Chances are it'd need to be pressed down under a flat board to get it planed flat - it's nothing like as rigid as a hardwood, or even as a plastic like Delrin. (acetal). It might not end up dead flat per se, but if it as a result was of uniform thickness then maybe it could be screwed to a fence. That too might bring issues if it was tethered too tightly - it moves about ten times as much as aluminium with changes in temperature.

UHMW by the way is normally ultra high molecular weight polyethylene. What it does have is great wear resistance and very low friction. (it's very slippery)

ian

[Sam Murdoch]

No idea how to flatten it either but as for holding it down I find that the best fastenings are euro screws. The head can be flushed or under flushed nicely with lots of bearing. For whatever it's worth I prefer the euro screws to conventional flat heads in this application. Have had great success especially with 1/8" thick UHMW strips.

[glenn bradley]

I use UHMW tape with good result. Available from most of the usual suspects:

http://www.amazon.com/UHMW-SLICK-TAP.../dp/B00153EJ5S
http://www.woodcraft.com/Product/200...s-3-Width.aspx
http://www.woodworkingshop.com/product/bh19430/

[Ryan Baker]

For a fence, just get the thin (1/8"-1/4" thick) strips from somewhere like Peachtree. They are already have smooth surfaces, and are sized right for fences. Then attach it to a flat subfence (it will conform to the subfence).

[Lee Schierer]

Should be UHMW...Ultra High Molecular Weight. Common term for the teflon, nylon, delrin etc. plastics used for fences.

UHMW is short for Ultra High Molecular Weight Polyethylene. It is not related to teflon, nylon or delrin, which are all different plastics which are also not related to each other. It is slippery and will wear better than steel in abrasive environments. It was originally used as dump truck bed liners and for chain guides on chains at logging mills. It can be worked with woodworking tools (table saw, router, jointer, planer, bandsaw, and most hand cutting tools), but the shavings will be like clingy snow. UHMW has a temperature limit of about 180 degres F. It get clear as it gets hot and will burn before it melts to the point where it will flow. It cannot be injection molded, but it can be extruded or forged. It is flexible so it is not suited for structural purposes, but works exceptionally well as a wear layer or sliding surface.