Delrin

PetarB · Post by **PetarB** » Mon Nov 14, 2011 12:18 am

Anyone used delrin? I heard it turns well on a lathe. Does it cut well otherwise? Glue? Best online provider?

southwestforests · Post by **southwestforests** » Mon Nov 14, 2011 12:23 am

Model RR parts such as freight and passenger trucks are commonly made of Delrin. And axles for metal wheelsets.

Tough, somewhat flexible, for model RR use, it is slippery enough to be considered somewhat similar to having "self lubricating" properties.

It often does not like glue or paint.

Kylwell · Post by **Kylwell** » Mon Nov 14, 2011 12:51 am

Delrin cuts wonderfully on a lathe but it's in the family of low energy plastics, i.e. nothing like to stick to it. One of the reasons it's popular in surgical equipment.

Mr. Badwrench · Post by **Mr. Badwrench** » Mon Nov 14, 2011 1:03 am

Delrin is in the same family of plastics as teflon and polypropylene. It is specifically designed to be non-reactive, and requires special glues to stick to it at all. You could make a good CA bottle out of it though.

If you are looking for a plastic that machines well, and can be painted and glued with common solvents, try polycarbonate. It is somewhat softer than acrylic, but just as clear. It doesn't chip like acrylic when machining. It glues with most model cements, (Testors, Tamiya, Tenax, Ambroid, etc). And it is about 1/3 the price of Delrin.

DennisH · Post by **DennisH** » Mon Nov 14, 2011 7:58 am

We have a recumbant exercise bike that had super cheap bearings that would get destroyed with even the slightest amount of use. I replaced them a few times before I finally had enough of the B.S. and turned a pair of solid Delrin "bearings" that fit the whole profile of the original junk bearings. They've held up wonderfully, turned easily and saved me a lot of $$$ because I was going to throw the danged thing out.

Like the other guys said, it glues for $#!7, but it's not meant to be.

McMaster-Carr has a great selection of materials, give 'em a look-see.

Dennis

Blappy · Post by **Blappy** » Thu Dec 15, 2011 8:29 am

I think it's super expensive too. They make competition YoYos out of it too. I was going to make a custom one for a relative but the piece I needed for it was really expensive.

Joseph Osborn · Post by **Joseph Osborn** » Thu Dec 15, 2011 1:43 pm

Since this thread has been resurrected, I'll chime in too: my experience with delrin on my Taig lathe has been good. It cuts like butter but it actually cuts better with a dull tool because a sharp point "digs" into the surface and leaves a rough finish. As mentioned, you can't glue delrin like you can other plastic, but for making casting masters it's great. I think I got my pieces from Onlinemetals.com.

Kylwell · Post by **Kylwell** » Thu Dec 15, 2011 2:24 pm

What you want is a very sharp bull nose (rounded) bit to peel the plastic off. Sometime known as a finishing bit for fine finishes on metal IIRC. I shaped my own with a Dremel grinding tool and a file.

Joseph Osborn · Post by **Joseph Osborn** » Thu Dec 15, 2011 3:09 pm

Kylwell wrote:What you want is a very sharp bull nose (rounded) bit to peel the plastic off. Sometime known as a finishing bit for fine finishes on metal IIRC. I shaped my own with a Dremel grinding tool and a file.

...Which won't work if you are turning a shoulder and want a sharp transition. The round-nose tool works well for finishing but will not get into the corners.

Here's a link to a little part I made with delrin where you can see the slight gouging in the inside flat face from using a very sharp corner tool, in this case a sharp boring bar:
http://i101.photobucket.com/albums/m72/ ... 154805.jpg
Cosmetic appearance wasn't important for this part, but the outer diameter was finished with a dull right-hand tool and came out really smooth.

PetarB · Post by **PetarB** » Sun Jan 08, 2012 6:41 pm

Wow Jospeh that turned out nicely! Now I really want to get some! How does Tamiya primer or other lacquers stick to it? Any experience?

Joseph Osborn · Post by **Joseph Osborn** » Sun Jan 08, 2012 10:37 pm

PetarB wrote:Wow Jospeh that turned out nicely! Now I really want to get some! How does Tamiya primer or other lacquers stick to it? Any experience?

Thanks; I have never tried to paint it myself since all the parts I have ever made with delrin were meant for molding. I did a quick google and found that painting is problematic but not impossible.

Tankmodeler · Post by **Tankmodeler** » Mon Jan 16, 2012 8:05 pm

Paints & primers don't stick to it either. The same properties that make glue not stick, make paints not stick.

outlander · Post by **outlander** » Fri Feb 03, 2012 12:54 pm

Mr. Badwrench wrote:If you are looking for a plastic that machines well, and can be painted and glued with common solvents, try polycarbonate. It is somewhat softer than acrylic, but just as clear.

WRONG! Polycarbonate is NOT softer than acrylic! Polycarbonate is nothing at all like acrylic, except that they're both clear. MAKROLON is polycarbonate, and is much more expensive because of it's hardness. It's also what lightsaber blades are made of because it won't shatter the way that acrylic will. Acrylic is what plexiglass is made of. Superglue will hold both, but this is only because it dries to the surface. Polycarbonate won't stick permanently like acrylic will when superglued - you have to weld it. Even acrylic won't stick too well with it either since superglue itself is so brittle when dry. You might want to use weld-on cement as it's meant for plastics, and is solvent based. It melts the two surfaces together for a stronger bond.

Delrin is a low solvent based plastic - not "low energy". Meaning that it doesn't like solvent based products. Elmers glue works real well when attempting to bond it to something else. I say "attempt" because it depends on what you try to glue delrin to. Not all surfaces will stick to each other no matter what you use since not all materials mend to each other, or have the same reactivity to glues - solvent based or not. Delrin is one of these materials. It's meant to be slippery, and allows for low friction, so it isn't the best material to build a typical model from. This is used for bowling lane alleys, bowling balls, and other products that need a low friction application.

Kylwell · Post by **Kylwell** » Fri Feb 03, 2012 1:20 pm

Common versions of polycarb are indeed softer than common forms of acrylic (aka Poly(methyl methacrylate)). Both are thermoplastics and both have similar glueing properties as far as most modelers are concerned. Having machined both I far prefer acrylic, tho' Mr Badwrench prefers polycarb. Both require very sharp tooling with a lot of relief.

Delrin, aka Polyoxymethylene, is a low energy plastic because both homopolymer and copolymer have chain end groups (introduced via end capping) which resist depolymerization. With the copolymer, the second unit normally is a C2 (ethylene glycol) or C4 (1,4-butanediol) unit, which is introduced via its cyclic acetal (which can be made from the diol and formaldehyde) or cyclic ether (e.g. ethylene oxide). These units resist chain cleavage, because the O-linkage is now no longer an acetal group, but an ether linkage, which is stable to hydrolysis. POM is sensitive to oxidation, and an anti-oxidant is normally added to molding grades of the material. Which is why they're a bitch to glue unless you surface treat it.

Just Plain Al · Post by **Just Plain Al** » Fri Feb 03, 2012 1:25 pm

At the shop I work in we machine bearing surfaces for prosthetic legs from Delrin. We specifically use Delrin because glues, paints, and solvents don't stick to it and it is basically self lubricating. The leg manufacturer has tried many alternatives but always comes back to Delrin.

Google "Ferrier Industries" if you wonder what the prosthetics look like complete. Pretty interesting application. We don't produce the legs, we sub-contract for parts.

Blappy · Post by **Blappy** » Fri Feb 03, 2012 1:36 pm

I personally hate machining either Acrylic or Polycarbonate. I find them both too "melty" and brittle. If I need something clear or translucent I will cast a cylinder of corresponding resin and turn that. You can also glue it with superglue quite easily.

I had one too many experiences where I was turning a delicate parts from Acrylic and was almost done only to have it rapidly and energetically disassemble itself. The last time that happened I had a small shard of the stuff protruding from my forehead right above my safety glasses.

Kylwell · Post by **Kylwell** » Fri Feb 03, 2012 1:41 pm

Ouch!

Machining acrylic can take a delicate touch. I think that's partially why Brad prefers polycarb, he can take huge cuts out of it. It's much more forgiving to such abuses.

Blappy · Post by **Blappy** » Fri Feb 03, 2012 1:46 pm

Kylwell wrote:Ouch!

Machining acrylic can take a delicate touch. I think that's partially why Brad prefers polycarb, he can take huge cuts out of it. It's much more forgiving to such abuses.

Most definitely. It's not good for really thin walled rocket engine bells. You can reef on Smooth Cast resin really hard.

Kylwell · Post by **Kylwell** » Fri Feb 03, 2012 1:47 pm

I have found Aves to be a joy to machine. Never tried Smoothcast.

Mr. Badwrench · Post by **Mr. Badwrench** » Sat Feb 04, 2012 12:23 am

Just Plain Al wrote:At the shop I work in we machine bearing surfaces for prosthetic legs from Delrin.

Do you use natural delrin or delrin AF, (delrin impregnated with teflon)? I'd think that delrin AF would be superior for bearing blocks, but I don't know what sort of restrictions you might have for prosthesis.

Just Plain Al · Post by **Just Plain Al** » Sat Feb 04, 2012 1:32 am

Mr. Badwrench wrote:
Just Plain Al wrote:At the shop I work in we machine bearing surfaces for prosthetic legs from Delrin.
Do you use natural delrin or delrin AF, (delrin impregnated with teflon)? I'd think that delrin AF would be superior for bearing blocks, but I don't know what sort of restrictions you might have for prosthesis.

Natural Delrin but I'm not sure why.