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Is this stuff very different from UHMW? How is UHPE for machining ? How does it cut, drill, tap and sand ? How does it compare to machining UHMW and Plexi ?

I think it is the same stuff. UHMW stands for ultra high molecular weight and is referencing polyethylene or PE. UHPE is ultra high polyethylene.

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Steve Walden
Aspiring Builder,
Bartlesville, OK

I've tried machining every type of PE that I could get my hands on. They all machine pretty similarly - like butter, but with very stringy burrs that are hard to get rid of. The harder it is, the cleaner it machines, but de-burring is still a PIA.

When I Googled it, it turned out to be them skipping different letters in the full acronym (UHMWPE). UHMW == UHPE == UHMWPE.

Anyhow, I think Sheldon's more or less on. They're all easy to deburr with a scalpel or razor if you're very handy with one but be careful not to take too big a chunk out of the edge if it matters (or your hand)!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I guess the standard deburring tool would work. I thought that UHPE might be a little bit harder then UHMW and be easier to tap and hold the treads. But after googling both this morning it does seem they are the same.
You all have any insights on Corian?

What about using Marine board, HDPE? That's what I made my Wells/Sylvan jig out of. Its seems hard enough to tap without problems, at least none so far. Its not as brittle as Corian.

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Aoibeann

Yeah me too. I was looking for something a little more hard. I don't like how UHMW drills or taps but looks like I might use it since I have some on hand.
What's marine board?

Marine board is a commercial version of HDPE.
http://www.sdplastics.com/marine_board.html

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Aoibeann

Chris,

Have you tried working with Delrin (available from McMaster Carr, among others)? It drills and taps nicely. We use it for fixtures at work and I use it around the shop too. It's a bit pricey but so is UMHW.

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Steve Smith
"Music is what feelings sound like"

Doesn't Durlin have a higher friction coifencent than UHMW? or have I got that backward?

Well after a quick Google, Yep UHMW has a lower friction coefficient than Derlin and is self lubricating as Derlin is not. Durling is good where rigidity is the main goal UHMW is better where low friction is the goal. Of course a bit of high strength carpet tape and you can marry the two

Steve, no I haven't ever used it and don't know anything about it. I'll look into it and see what I can find out about it.

Delrin does have a higher friction coefficient but it is still reasonably slick. Maybe you can get a small piece to check out. Most glues will not stick well to it. I used some as a form for part of my rosette and the CA just popped off. It does machine really nice - if you need something that is very slippery then UHMW is probably your best bet.

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Steve Smith
"Music is what feelings sound like"

I made a plunge router carriage from UHMW and the problem I am having with UHMW is that when I cut the circle out for the router mount and slot it the slot closes up. If you look at the picture, the area that the pencil is pointing to will close up if the router is removed. The UHMW doesn't hold it's shape and this makes adjusting the carriage so that it slides up and down on the rods pretty tricky. Do you know if the Delrin will hold it's shape in this case?

I believe it will. I know it will work with smaller holes but haven't tried that geometry with a hole that large relative to the material thickness. As luck would have it, I have a 6" square cutoff of 1/2" Delrin with a 4 1/2" hole in the center left over from my rosette project. Tomorrow after work I will cut a slice on one side and see what it does. I'll post back tomorrow night.

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Steve Smith
"Music is what feelings sound like"

Chris...could you make that part of your carriage in 2 pieces? The top piece would have a hole for the router that was slotted so you can tighten it to the router. The bottom piece would have a hole for the router but no slot. This bottom piece would also hold your bushings that the pins run through. Then you put a couple of screws through both pieces to hold them together. I am terrible a describing this stuff...here is a picture. Hopefully this will make more sense.




By doing this your guide pins will be going through a piece of plastic that can't flex because you don't have a slot in it.

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Jeremy Vonk

That might be an option but would take up additional material and space to fit it in. This is a Bishop Cockran knock off. here's another view minus the springs and plunge stop and cut depth adjusting knob.

Chris,

I cut that piece of Delrin and, as expected, it remained dimensionally stable.

A transducer mount I machined sometime ago along with the hole in the scrap piece of 1/2" stock. I think Delrin machines kind of like soft aluminum.


I used a 3/4" Forstner bit to make a "channel". I haven't done any deburring here which shows it's not as soft as UHMW. Cuts much cleaner.


I let it sit for a while and measured it. As expected, no shrinkage.


Don't know if that helps. If you were closer I could give you some scrap to try.

Since I had to figure out how to post pictures, here's my first rosette I just finished. Several things I won't do again but, hey, it's done and time to move on

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Steve Smith
"Music is what feelings sound like"

Thanks Steve,
Interstate plastics seems to be reasonable on prices for Delrin. I'll probably give it a try to see How I like it. Looks promising.
Nice Rosette!

Chris, one other thing you could try is to drill the guide pin holes with the "clamp" under tension. Clamp the router or something that simulates the diameter of the router in there and then drill the guide pins. Then your guide pins will always be in alignment when the router is installed.

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Jeremy Vonk

Yeah, I already thought of that but I already have it drilled and I'd rather find a better material that I don't have to worry about doing that. I also have thought of just making it out of Aluminum which isn't that much different in price.

Hey guys not to high-jack but I have a question about UHMW while you are discussing it.

The guy who sold me his table saw also gave me some UHMW and said that if I install a 10" blade in the saw backwards it cuts this stuff like butter and leaves a near perfect edge, kind of burnished, and no deburing required.

Have you ever heard this before or done it?

Thanks!

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Ann Arbor Guitars

I used to do the reverse saw blade trick to cut PVC pipe and it worked well for that application. For the 3/4" UHMW I cut, I just used my 10" miter saw and went reasonably slow and easy. Too slow a cut might melt the plastic. The cuts I made came out fine but I did chamfer the edges a bit with a small plane.

I haven't tried the reverse blade trick on thicker plastics.

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Steve Smith
"Music is what feelings sound like"

Are you talking about a carbide tooth blade? I've turned a circular saw blade backwards and cut aluminum flashing. I cut my UHMW with my 10" carbide 60 tooth blade with no problem and clean up the edge by scraping it with a razor knife. Takes a second. If i want to round the edges some as I usually do it's to the belt sanding station.