New cruwear, your opinions on my concerns with defects please...

ssgwhite

ssgwhite

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Aug 26, 2012
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So I just got my Cruwear Military in the mail from a reputable dealer. I opened it up and was very impressed with the knife overall until I got to looking at the edge. Back towards the ricasso near the plunge is a slightly uneven sharpening grind. I looked at a bunch of pics online and didn't see it on them. The more I looked I saw what appears to be a straw color starting to go blue, like it overheated during the sharpening. I know these knives are prone to patina; but there's no other signs of patina anywhere else and this spot just looks different. The pic doesn't really capture the colors (straw to brown to blue) all that well but the more I look at it the more it concerns me. I purchased this knife just for this steel; could that have effected the temper/heat treat of this blade in that spot? What do you think; am I just being too picky or are my concerns reasonable? Thanks, Anthony
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Can not really tel from the picture but if it is right on the edge it could be from overheating. It is a production knife and has that possibility, however usually Spyderco has very good quality control and I have not seen a problem with their grinds from the knives I hav handled. I have no experience with the Cruwear steel though.
 
I added another photo; its really difficult to get to show in pics, but is much stronger in person. You can see some discoloration on the other side as well, but its more difficult to see.
 

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The grind is typical. I've seen it on pretty much every Spyderco that does not include a sharpening choil/Spanish notch. The color could be from something that was on the belt grinder, or patina. I suppose it could also be from over heating the blade at that point but since that area was not ground as much, it should have been heated less, rather than more, so my money would be on one of the more benign explanations.
 
Since you bought it from a dealer, you may as well be 100% happy with it regardless if performance is affected. You can see if the dealer has another to send to you or contact spyderco hq to see if they can replace it. Better act fast before stock runs out of this sprint.
 
There's nothing wrong with the blade. The area the discoloration it's in is too thick to have heated up that high without having worse effects showing. In addition, it takes a thousand degrees just to temper this steel ( lower the hardness by a point or so if held there 15 minutes). It's the tungsten in the steel's composition that mitigates the affects of the heat and almost makes this a high speed steel.

If you took some solvent, or even a blade polish it would remove the color. In fact I'll state that paste wax such as museum grade Renaissance wax would micro polish it out.

You guys here can be way too quick to call "defect". I'm all for being happy with a knife or other purchase but think things through. Burn marks have a unique look to them, stains another. Steel that is damaged will have a visible difference in looks between the damaged and regular steel almost like a hamon.

Not real good images but still something to look at: http://www.ibgndt.com/grinder-burn-detection-pmft-eddy-current.php

Thanks,

Joe
 
Joe,
I appreciate your input, I've seen your posts and have learned a lot from them. I think I remember reading that you had a bit of input on this steel being used in this knife. I see you said that it takes 1000* to temper this steel; what temperature does it have to hit to turn to a straw color?

"The area the discoloration it's in is too thick to have heated up that high without having worse effects showing"
The pic may not show it well but the discoloration starts at the edge and works its way up; at a place where the edge was ground more than the rest. I don't know of a thinner place on the knife than the edge.

"You guys here can be way too quick to call "defect". I'm all for being happy with a knife or other purchase but think things through. Burn marks have a unique look to them, stains another. Steel that is damaged will have a visible difference in looks between the damaged and regular steel almost like a hamon."
I'm no metallurgist, but I would think it could mess with the heat treat having the edge turn colors during sharpening, and that's all I was really asking about. I would think one that heated enough to hit a temper color would have a lower hardness than one that didn't.
 
I think its an optical illusion, and the plunge is really ground less. I've run race pistols hot enough to change colors, and it is the oil that changes color. I know they aren't over 300 degrees because I can hold it and it will feel really hot but it won't burn my skin.

I think it could just be a corrosion inhibitor responding to warm temperature, maybe having something to do with the plunge line.
 
Maybe; but I would think if it were oil or a rust inhibitor it would come off when I cleaned it. I think I'm just going to keep it; I shouldn't be so picky sometimes. Thanks to everyone who commented, it's really appreciated.
 
I don't think it is heat since it is so high up on the blade. I'd use it and not worry at all. Any mild metal polish should probably take it away with a bit of effort.

An other option is degreasing it and giving it a nice gray patina with some warm red wine vinegar ;)
 
I think I'm going to do a hot white vinegar (don't have red wine vinegar) and maybe a stonewash after since I'm keeping it. Its not high up at all though, it starts at the edge. I just can't get the pics to pick it up.
 
It is just that if it was heat discoloration from sharpening I don't think it would go that far up from the edge.
 
Its a type of steel that this particular knife is made of. NoFair: I hear what your saying, it seems pretty thin there but you're probably right.
 
NoFair said:
It is just that if it was heat discoloration from sharpening I don't think it would go that far up from the edge.
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Agreed. If the blade had been heated enough to turn that area straw color, the edge would be blue or purple over a good-sized area. The thinner section of the blade in that area would have gotten much hotter.
 
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