knives in the freezing cold....epoxy fail

timos-

timos-

Knifemaker / Craftsman / Service Provider
Joined
Oct 22, 2012
Messages
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I had a little kiridashi come back to me recently.
This is .05 thick CPM 3V with some black wood scales and a couple carbon fiber pins.

The end user told me he left it overnight in his car ( probably around 20deg. that night) and the next morning he snapped this pic:
O8EDYCK.jpg



It is a little hard to see in this picture, but the knife was obviously used to pry and the whole thing is bent. The scale cracked like this b/c it is cross grain, but it also appears the epoxy failed. It would be my first (known) epoxy failure since I started using west systems G-Flex. My question is what role do you think the temperature could have played in this failure?
 
Surely low temp couldn't cause that looks like it's been abused takes extreme temp changes very quickly to do that kind of damage
 
Ouch. That hurts just looking at it. Looks like someone was pushing and twisting with a fair amount of force. I'm not sure that at that thickness of stock material and force a failure could be avoided.
Edit to say that it makes me curious as to what it would look like had there been corbys instead of pins as I tend to use a lot of corbys.
 
Mechanical fasteners prevent things like this. I can't understand why people don't use them.
 
Certain epoxies do shrink/expand like most materials do, to what extent would vary. Some epoxies can get brittle with the cold but I don't think 20 degrees is near cold enough but I could be wrong. If there were some bonding issues on the surface I could see that pulling away more easily if there was already a break in the material.

I would think the bond was weakened by the prying and break as many epoxies don't handle vibrations well as they're too stiff and/or brittle. I ran into this commonly when trying to do cheap fixes on a sport motorcycle I took to the track a long time ago using JB weld or similar and the cracked plastics just re-cracking.

I think epoxies usually have a spec sheet on how much they shrink per degree change or what temperatures they're good for. In my workings with epoxies it usually the high side we're worried about but we frequently get questions on the cold "can I use carbon fiber in the winter?" "Yes."

Disclaimer: not an expert in epoxies I've only dealt with them recreationally for things like boats, bikes, and motorcycles.
 
Bill DeShivs said:
Mechanical fasteners prevent things like this. I can't understand why people don't use them.
Click to expand...

How would a mechanical fastener have stopped the scales from cracking from the prying? Wouldn't the wood have cracked from the abuse regardless?
 
I think the question here is was there abuse, or did this just happen due to temp?
I don't think that this just happened while sitting in his car, no way.
Would I replace it anyway? Probably.
 
wouldnt it be exciting if everything around us started to break when the temperature gets to 20?

dishonesty and knives dont mix well with my emotions, knives are never dishonest, that one says it was abused.

the "best" thing to do would be to fix the handle with new wood, and tell him not to do it again. (while i think a cheap CA glue fix was earned its not good workmanship)

your time is more valuable than anyones lies, dont forget to charge him for a new handle. sorry about the knife, hope you get this all sorted out.
 
How important is it to keep this guy as a customer? I've replaced items I've sold, but called people out on their bs. (When I was doing custom bicycles- they were always just riding along, or left it in the garage overnight. :jerkit:) Id replace it, and say you know it wasn't because of the cold. But you won't replace another one.
 
milkbaby said:
How would a mechanical fastener have stopped the scales from cracking from the prying? Wouldn't the wood have cracked from the abuse regardless?
Click to expand...

G10 for had use knives with 3v or other tough steels. However, this is really thin 3v, and flex is based on geometry, not steel. The knife was abused, period.
 
milkbaby said:
How would a mechanical fastener have stopped the scales from cracking from the prying? Wouldn't the wood have cracked from the abuse regardless?
Click to expand...

It would have stopped the scales from lifting.
 
Nah, that wasn't cold temperature that did that. Many knives of mine have been left out or in use much colder than that with no signs ever of failing epoxy.
 
It quite certainly look like it was used to pry something.
But you could give him the benefit of doubt and do a quick test of your own by using some scrap steel and some scales from the same batch/supplier. It could be like bikerector said before that the epoxy got brittle or shrank a bit too much in the cold. Plus it would give you the peace of mind and you could call him out on his bs.

Conflict breeds creativity
 
I've left blades out in the car in negative 50 or colder before (not on purpose) and have never seen a failure from cold alone.

I wouldn't recommend USING the tool while it's that cold of course, but blaming that on cold? Please... :jerkit:
 
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