Evidence of overheated steel??? Discoloration.

Nosetotail

Nosetotail

Joined
Jun 10, 2007
Messages
398
I'm not sure where to put this question but here goes.

I got my brand new Endura 4 with zdp a couple of days ago, and I have already profiled the edge to my likings however I am a little concerned about something I saw on the back side heal of the blade. It was around the knurled section just before where the knife enters the handle around the pivot area.

I can see some blueish black discoloration characteristic of heating steel. It blends into a brownish hue as it gets closer to the pivot. I understand that they have to heat the steel to heat treat, but I was a little concerned about this as the rest of the knife is polished clean. I am wondering if this is common in quality knives or should I be concerned.

I've only had one other quality knife and I don't remember if I saw anything like this on that one. I only got concerned as I have seen a couple of references on here about a bad heat treatment. I can get a pretty good edge, but I haven't had it long enough to base an opinion on. So far, I don't think I could have picked a better knife. The price is right and the quality is even better.
 
Sounds like discoloration from the laser cut. Kinda hard to say as I'm not sure where you are describing.
 
On the back side of the blade along the spine where the big grooves are cut into the knife right at the heel behind the thumb hole right at the pivot point. The discoloration is right in line with the laser cut lettering, but it is almost a half inch away.

As I'm describing this, I'm thinking it may be from when they cut the grooves or knurls. I don't know what they are called and I'm not sure what their function is, but a lot of pocket knives have them. I geuss it is so you get a better grib as you are sticking something, but as of yet I haven't used my knife for stickin.

I wish I could post picks, but I haven't a clue how.

The color is real light, but it is certainly from heat.
 
I got an Al Mar Nomad a while back that had discoloration on the blade. I sent it back and they said that the blade hadn't been buffed out properly but that it was perfectly fine functionally. They replaced the knife anyway.
 
I'm perfectly fine if the discoloration is a normal thing, and that I only see it because it might not have been buffed. Perhaps they can't buff the knurled section that well anyway. If I knew that all blades had this color before buffing, I don't think I would be concerned, but I wouldn't know. I don't think I want to send mine back unless there is cause for concern.

I have already taken quite a liking to it, and I just don't want to think something is wrong but I figured it wouldn't hurt to ask.
 
Yes, they're all discolored before finishing. I'm sure it's just a spot that didn't get cleaned up. You can polish it yourself or just ignore it.
 
Thank You. I wasn't that concerned after I profiled it and got a decent edge without issues. Although I just can't quite get back to that factory edge sharpness. Of course I had to ruin it freehanding with my light bulb filament.
 
Generally speaking, any discoloration in the steel is negative. It means that the steel has been heated to "tempering" temperatures. This means that the steel have somewhat changed characteristics, f i lower hardness.

It's difficult to say exactly how much your knife will suffer from this, but I would send it back.

Discoloration is always a sure sign of overheating, this is especially important when grinding the knife.
 
Any good book on heat treating will give a "library" of temper colors. I remember having some A2 tool steel parts vacuum hardened and tempered rock hard. They had a pretty purplish color to them. The real problem is that you can have a part that is heat treated totally improperly and one that is done perfectly and there can be no way to tell them apart visually. You can easily tell them apart by metallographic tests but you need a laboratory. The way most poor heat treating is discovered is when the part fails!
 
You must log in or register to reply here.
Back
Top