Quick question: is this delrin?
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    Question Quick question: is this delrin?

    I bought a hunk of blue(?) delrin off eBay because a machinist friend told me it was nice to work with. I've seen delrin parts, and am wondering if what I got from eBay is the real thing. I've never encountered what this stuff is doing, peeling in strings like a piece of celery (see photo). Can someone with experience comment? I'm not a true machinist myself, but am able to use a bandsaw to cut this, grind the edges smooth on a belt sander, and drill and tap some holes. Before I try, I'd like to have some confirmation. If this definitely is NOT delrin I'd send it back before cutting it. Any comments, suggestions, guffaws welcome Many thanks.

    dscn5352.jpg

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    If that is delrin it’s definitely not the standard homo/copolymer resins most think of with acetal or acetron. Generally delrin is black or white though other colours are available but I would be hesitant buying mystery drops that were anything but those two.

    Look up plastic burn testing and see how it fairs with that. You can probably narrow it down to something.

    Burn Test Identification for Plastics | Boedeker

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    Hey, thanks for that link; very useful. Well, I put a temperature-controlled soldering iron set to 500 degrees against it and it did melt, and it does burn with a blue flame. That seems to indicate that it's acetal, so it must be the right stuff. I'll take a chance and cut it up. It was pretty cheap, another reason I thought it might be bogus.

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    It’s hard to say from the picture but the way the strands are formed and “peel” might lead me to believe it could be Cast Nylon of which blue is a fairly common color

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    My Dad the chemist could tell by smell.
    By picture... not so much.
    That said “delrin” comes in lots of colors...and I’ve seen that shade of blue.
    The cutoff end looks about right.
    If it’s cheap, give it a shot.
    Unless it’s made of cheese it will probably be OK.

    Positive cutting angles and climb machining can handle most “plastics”.

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    Miguels244, maybe the OP can re upload with a scratch-n-sniff version?

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    Quote Originally Posted by Electrojim View Post
    ...I'll take a chance and cut it up. It was pretty cheap, another reason I thought it might be bogus...
    Yeah, it looks like it's about 8" square--not exactly gonna break the bank if you have to replace it with known material. Ebay is a great place
    but "mystery" material is just that--no guarantees of authenticity...

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    does it smell like delrin when you cut it ? or does it have almost no smell like UHMW?

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    Ive turned blue Acetal in the past for the food industry. IIRC the blue color is for easy identification of broken pieces in the food product when parts break or wear. This acetal should also be slightly magnetic so sensors can detect broken pieces.

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    Take a lighter to it and if the smell knocks your head clean off of your shoulders, its delrin

    If it just smells like burnt plastic it is not

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    Don't look like any Delrin I've ever cut...

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    Argghh. You can say acetal, but Delrin(R) is a registered brand name and so is capitalized. DuPont Delrin® is a homopolymer of formaldehyde (its a polyoxy-methylene.

    Tecaform™, Ultraform® and Celcon® are brand names for copolymers made by other firms.

    If you had a test setup and wanted to differentiate, the homopolymer is stiffer than the copolymers.

    This polymer identification chart seemed useful. According to the chart, burning acetal smells like formadehyde.

    http://www.consultekusa.com/pdf/Tech...20chart%20.pdf

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    [QUOTE=bosleyjr;3218256]Argghh. You can say acetal, but Delrin(R) is a registered brand name and so is capitalized. DuPont Delrin® is a homopolymer of formaldehyde (its a polyoxy-methylene. Tecaform™, Ultraform® and Celcon® are brand names for copolymers made by other firms. If you had a test setup and wanted to differentiate, the homopolymer is stiffer than the copolymers./QUOTE]

    ˆˆˆBRAVO. When you order Delrin® over the phone you always have to say DuPont Delrin® or they will substitute Celcon®, which is the very definition of "cheap imitation."

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    If you have a known piece of acetal, run your knife (or deburring blade) down a sharp edge. Listen to the sound.
    Delrin (acetal) sounds different than HDPE, UHMW, Nylon, Nylatron, etc....
    The difference in sound is easily distinguishable from other plastics, takes no time whatsoever, and no toxic fumes from burning.

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    Cool, Doug. I guess you need a test piece of acetal, thought.
    Last edited by bosleyjr; 08-08-2018 at 01:37 PM.

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    Okay, guys, here's an update. One thing I also noticed with this material is that it seems quite heavy for its size, which is 6" square (for $11 on eBay).

    Based on gustafson's and bosleyjr's notes, I set fire to this stuff once again. Steady blue flame, no smoke, no smell at all!

    Then I went out in the garage and put a flat edge of the piece against the belt sander. No 'sawdust' at all, just a mess hanging off the exit side (see photo). Next I drilled a #36 hole and ran a 6-32 tap in. The stuff drilled okay, long continuous chip coming out (see photo), but the tap squeaked as it went in and very little material was actually removed (the small bits in the photo).

    dscn5353.jpg

    You know, at this point I really don't care much what material I use for my project; I just was told that Delrin is a pleasure to work with. To prove the design I first used a piece of 1/2" plywood. The for the first 'real thing' I graduated to phenolic material (the brown stuff made from cloth and whatever), which worked really well, actually. But based on the recommendation, I turned to Delrin, which I now think I got gypped on. Here's what I'm making:

    dscn5355.jpg

    The piece in question is that brown block, phenolic in this case. It's 1.3" square with a 30mm hole in the center. A saw slot allows this to clamp that metal part, an audio transducer, and hold it to the 1/8" backplate. I drill the 30mm hole with a Forstner wood bit, which is why I'm looking for a good material to fabricate from. I know, I know, I should be using aluminum, or at least milling that 30mm hole, but I'm not a machinist. So I need to be able to make these in small quantities using my band saw, drill press and belt sander.

    If there's a better material, I'll use it. The phenolic works, but it's rather brittle and I'm afraid to torque down much on those 6-32 screws holding it to the backplate. Something with a bit more 'give' might be good, and I don't want to tax the cutting edge on my 30mm wood bit of course.

    Thanks for all your help!

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    I have only bought Delrin in white or black and it has always been marked in any size that was large enough to be marked.

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    Quote Originally Posted by Electrojim View Post
    dscn5353.jpg
    Whatever that is, it certainly isn't Delrin/Acetal.

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    Looks like UHMW to me.

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    Quote Originally Posted by bosleyjr View Post
    Cool, Doug. I guess you need a test piece of acetal, thought.
    Yes, you would need a piece.
    I never even considered that a machine shop would not have a piece of delrin laying around.....

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