Delrin

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Real1shepehrd

Joined
Apr 25, 2023
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We've all seen the Delrin slabs that have shrunk. Has anyone ever tried to soak them with something to see if they might expand back....mineral oil....something?

Kevin
 
Dig around a little bit on the net and you will find that Delrin is a low end, multi-use resin based plastic that has been used in manufacturing for decades.

According to what I just looked up, the plastic/resin would probably have Teflon in it as well, no doubt to help prevent staining.

Since it is actually plastic and may have a Teflon component it is probably unrecoverable from shrinkage. Not much penetrates plastic or Teflon, but together can't think of anything. A couple of my old shrades from the '70s could sure use some help if there was something...
 
Real1shepehrd said:
We've all seen the Delrin slabs that have shrunk. Has anyone ever tried to soak them with something to see if they might expand back....mineral oil....something?

Kevin
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I collected Buck 303 for years..Mostly just the pre-in-house Camillus ones. Ive soaked them for up to 10 days or so in mineral to help de solve old factory oils and such. The delrin has never changed. As a plastic it is a sold material not porous so it takes on nothing by design.
 
Kettleman said:
I collected Buck 303 for years..Mostly just the pre-in-house Camillus ones. Ive soaked them for up to 10 days or so in mineral to help de solve old factory oils and such. The delrin has never changed. As a plastic it is a sold material not porous so it takes on nothing by design.
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I thought Buck uses Valox, not delrin. Valox appears to be a blend of polymers, while delrin is not.
Well, the yellow ones might be delrin.
 
dogstar said:
I thought Buck uses Valox, not delrin. Valox appears to be a blend of polymers, while delrin is not.
Well, the yellow ones might be delrin.
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Buck uses Valox. I collected old Camillus made Buck stockman. They were Delrin
 
Yeah, I know Delrin is synthetic/plastic and all that. But.....there has to be a REASON the slabs shrink. Like they outgas something, surviving in the air we breathe etc. I was just thinking maybe if the stuff was exposed to another substance or encouraged/forced to take something back into itself maybe using heat, it might make a difference. Just some rambling as I'm not a chemist.

Kevin
 
Real1shepehrd said:
We've all seen the Delrin slabs that have shrunk.
Click to expand...


Who is this "we" you speak of? You got a mouse in your pocket?
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I don't think I have ever seen Delrin shrink. Its quite stable, unlike other manmade materials that have been used for knife handles in the past. Post pictures of the knife in question....
 
Arathol said:
Who is this "we" you speak of? You got a mouse in your pocket?
ixaCKxv.gif

I don't think I have ever seen Delrin shrink. Its quite stable, unlike other manmade materials that have been used for knife handles in the past. Post pictures of the knife in question....
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I don't have to post anything. Look on eBay at Camillus BSA 'whitler' knives, #72, for example, and you'll see the shrinkage. In fact, there's one on there now NIB, absolutely pristine with shrunken slabs. So obviously it's not a 'use' issue or exposure to bad things......NIB is NIB.

Kevin
 
If that NIB knife you are referring to is this one -
EofGjzGl.jpg

that doesn't really look like Delrin, probably gutta percha or some other composite similar to delrin.
An older thread about this here-

Delrin Handle Shrinkage - All About Pocket Knives

What causes Delrin handles to shrink? Is it a natural process that occurs over time, or is there usually some type of
www.allaboutpocketknives.com www.allaboutpocketknives.com
 
Yeah, that's the one. Depends on what you read and who is writing it. There's a Russian guy that has a substantial collection of these.....some real beauties. I got into a discussion once with him about handle slabs.

I guess the definite answer would be promo lit from Camillus themselves when the knife was made.

My original knife like in the pic was bought in '64 when I was a Cub Scout. There's a long, twisted story about that knife. I still have it, but a 'knife maker' put modern slabs on it and essentially ruined its collectible value and originality. I did find another of the same vintage that does not have shrunken slabs.

I also wound up with the later 'version' of this whitler bought in the early 90's......which surprisingly, has value now.

Kevin
 
I'm not sure delrin shrinks. It has been used in billiards cues for decades and I think it is primarily due to it being very stable. I could be wrong but I have had several cues from the 60-70's by Tad, schon and others with delrin butt caps with zero shrinkage.
 
Delrin is dimensionally stable and does not shrink. That is why it is used on tight tolerance engineering parts. There are other plastics which do shrink and are not dimenstionally stable., especially if they contain plasticizers. So it is not uncommon to see knife covers that shrink, but that just means they are not made of Delrin.

And to answer the real question, "No, once a plastic shrinks, there's not much to be done about it."
 
knarfeng said:
Delrin is dimensionally stable and does not shrink. That is why it is used on tight tolerance engineering parts. There are other plastics which do shrink and are not dimenstionally stable., especially if they contain plasticizers. So it is not uncommon to see knife covers that shrink, but that just means they are not made of Delrin.

And to answer the real question, "No, once a plastic shrinks, there's not much to be done about it."
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If you read Page 47 of the DuPont lit provided by Arathol, Delrin DOES shrink with time & temperature and they give you the reasons why. I'm not sure why anyone would hold onto the absolute that Delrin doesn't shrink at all after reading that.......

Even a little bit of shrinkage will show up visually on knife slabs because of fitment issues.

Kevin
 
Real1shepehrd said:
If you read Page 47 of the DuPont lit provided by Arathol, Delrin DOES shrink with time & temperature and they give you the reasons why. I'm not sure why anyone would hold onto the absolute that Delrin doesn't shrink at all after reading that.......

Even a little bit of shrinkage will show up visually on knife slabs because of fitment issues.

Kevin
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LOL......Thats not at all what it says. Do the math....
Figure 41 says a 3.2 mm thick piece will exhibit less than .1% shrinkage (more like less than .05%) at normal room temp , ie below 30°C.
So, .1% (1/10 of 1%) shrinkage on a 3" (76.2mm) long handle thats 3.2mm thick means that part will end up .003"(.076mm) smaller, or about .038mm on each end of the handle. Thats half the thickness of a piece of printer paper...... Think you will even notice that?
Again, the text says "Years of experience with many applications have shown that parts of Delrin acetal resin molded in a hot mold (93°C [200°F]) will exhibit negligible post-molding shrinkage in most applications."
 
Real1shepehrd said:
If you read Page 47 of the DuPont lit provided by Arathol, Delrin DOES shrink with time & temperature and they give you the reasons why. I'm not sure why anyone would hold onto the absolute that Delrin doesn't shrink at all after reading that.......

Even a little bit of shrinkage will show up visually on knife slabs because of fitment issues.

Kevin
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And not to be "that guy" but...... Your knife blade Also expands and contracts with temperature. 😂😂😂😂
 
Arathol said:
If that NIB knife you are referring to is this one -
EofGjzGl.jpg
Click to expand...

That's a molded styrene product, it took the place of celluloid for a while before Delrin took it's place. It was noted for shrinkage. Old discussion - https://www.bladeforums.com/threads/cabone-handles.948411/ . Post #6 shows the Delrin scales from the same era, note the different jigging pattern. As mentioned, Delrin doesn't shrink to a noticeable degree.
 
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