Photo ID help - delrin or bone?

Parke1

Parke1

Joined
Feb 11, 2003
Messages
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It's on its way to me know from California, but I was wondering what some of our better trained eyes here thought.

This is an older Robeson I snagged off the big auction site. Initially I thought the covers looked like bone, but now I'm thinking maybe delrin. According to the model number that's stamped on the knife (the seller provided me with it), it could be either one.

Thoughts?

knife2.jpgknife1.jpg

Either way, I think it's a nice looking jack, so I'm not going to be crushed if it's delrin. Thanks for any help!

-Dan
 
I can't tell for sure from the pics but I can tell you that is not jigged like the derlin it is however jigged just like the bone used at the time. So I am on the fence also.
It a good looking knife.
 
Look at the material under magnification & very bright light. Bone will always show pores & 'grain'. Delrin never will. Under magnification, the plastic Delrin will still definitely look like plastic (too smooth, too uniform, and no pores/grain at all). Look for this on the lighter, un-jigged, polished portions, nearest to the bolsters. Even when highly polished, bone will always show the pores and grain, and Delrin will just look like a very smooth piece of plastic. Sometimes, the pores in bone can be easily seen by looking into the jigging marks (w/magnifier & bright light), at the ends of the mark where it's cut across the grain of the bone.

In time, you'll also be able to feel the difference under your fingertips, when handling & rubbing the material. Bone will feel much harder and usually a bit 'cooler' to the touch. Especially if you attempt to gouge it with a finger/thumbnail. Delrin seems to feel bit 'warmer' in-hand, and will almost always indent a little bit, when doing the same fingernail scratch test, leaving a little notch or scratch. Bone is much less likely to scratch under a fingernail; especially old bone, which becomes somewhat harder with age.

Polished bone will always show some glassy/watery 'depth' as well, especially darker bone. Much like a highly polished finish on a fine automobile, that often looks like you could stick your finger into and through it, as if poking into water.

From the pics, my gut tells me you've got Delrin there. But it's hard to see for sure, unless looking much closer.

The absolutely-for-certain, fail-safe way to distinguish bone from Delrin is to use heat. Destructive test, but Delrin always melts quickly if touched with a very hot needle tip. Or worse, if attempting to polish it with a powered buffer & compound, and lingering too long in one spot (been there, done that :D).


David
 
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Once I get the knife in hand, I'll be able to tell for sure. Thanks for the refresher course, David! That's a good set of tips for people new to traditionals!

That's my whole problem here, the pictures just aren't quite good enough to tell for sure either way. Hurry up, post office!

-Dan
 
Parke1 said:
Once I get the knife in hand, I'll be able to tell for sure. Thanks for the refresher course, David! That's a good set of tips for people new to traditionals!

That's my whole problem here, the pictures just aren't quite good enough to tell for sure either way. Hurry up, post office!

-Dan
Click to expand...

The jigging does look much more authentic, as usually seen on bone covers. The 'jigging' in Delrin usually is molded/cast into it, and it usually shows. But in the pics, I was trying (unsuccessfully) to see the grain/porous nature in the un-jigged portions, as well as looking for some of that 'depth' I described. Can't see it there, but that just means it needs a closer look. Hope it turns out favorably, to your expectations. Good luck! :thumbup:


David
 
But did Robeson actually use delrin?

From the pix, the uniform pattern looks more like delrin to me. Great capture whatever the material!
 
If that's delrin, it's the best dang jigged delrin I've ever seen. But I think it's bone.
 
I'm on the fence. I could really go either way. My gut is saying bone, but my eyes are seeing Delrin, so go figure.
 
can you heat up a paper clip with a lighter and push it on the bone?? if it is real bone nothing should happen but if it is the delrin bone it should go right into it. delrin bone is the fake plastic that just looks like the real bone right or am I have it wrong?
 
You're correct, Richard. I'm just itching to get this one in my hands and find out for sure!
 
When I can't tell if a cover is bone or synthetic, rather than putting heat to it, I have taken a scalpel and sliced a tiny sliver off. You can tell plastic when you cut into it, and rather than a melty spot, you have a divot that looks like part of the jigging. But I've only tested cheap yardsale knives, so you might not want to mess up this one.
 
richard thurman said:
can you heat up a paper clip with a lighter and push it on the bone
Click to expand...
:eek:

r8shell said:
When I can't tell if a cover is bone or synthetic, rather than putting heat to it, I have taken a scalpel and sliced a tiny sliver off.
Click to expand...

:eek::eek:


Golly Gosh Gee Whillerkers! fellas.

Dan doesn't want to destroy it. He just wants to know what it is.


Dan,
Wait till it gets into your hands, then post more pictures.
 
knarfeng said:
:eek:



:eek::eek:


Golly Gosh Gee Whillerkers! fellas.

Dan doesn't want to destroy it. He just wants to know what it is.


Dan,
Wait till it gets into your hands, then post more pictures.
Click to expand...

You're right, of course. I've just been been playing with modifying cheap knives, so I'm in a reckless mood:D
 
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