Mirror finish removes temper?

Ezaske

Ezaske

Joined
Sep 14, 2010
Messages
62
I read over on the Khukri House (KHHI) site some time ago that for their kukris a mirror finish can result in a softer blade. They imply that the heat generated by buffing can soften the temper (of the whole knife). This seems nuts to me. I thought the steel had to get glowing hot before it was annealed (400-500 def. F). Does anyone have any experience with this? H.I. Does not have the same "mirror finish" warning, but some people have mentioned that their kukri had to be sharpened a few times to get down to the hard edge under the mirror polish.
 
Yes, the heat from overbuffing a blade can cause problems with the heat treatment.
In the most extreme cases it will ruin it, but it cannot completely remove a temper.
Sometimes when the blades are buffed near the edge, a thin skin of annealed metal will form over the hardened steel. It is easily remedied by sharpening the blade down to the hardened steel.
 
Yes, all of the HI products I've had had a few thousanths of an inch thick layer of soft steel on them (the polished ones). It's from polishing them too fast (done properly, it wouldn't overheat the blade, but would take a lot longer).

You can easily tell. When I get mine, I just hit the edge with a file until the file just skates across the hard metal (provides a quick way to convex the edge, so it does have an advantage).

The overbuffing seems to also dull the edge -- I don't think they put much effort into keeping an edge on what they undoubtedly consider a decorative knife.

The Villagers (sand/scothbrite the forge scale off) and True villagers (forge scale left on) come sharp, with no soft layer of metal on them. I think that's the reason villagers and true villagers have become popular lately by guys that are intending to use them.
 
If the blade is kept cool while buffing it shouldn't be a problem. I sharpen my khuks on a belt sander so I haven't noticed any particular variation from villagers to polished blades. I suspect CPL Punishment is correct about why polished blades are duller than villager models, however.

Andy
 
That's just it, i don't think they worry about keeping them cool, I think they get it done as fast as they can.

I've polished many a thing, and I know when I was starting out in my profession, I got some things a little too hot and they annealed to a shallow depth.
 
having a buffed a few things myself, I can also say that it is easy to get things too hot but I haven't gotten anything glowing hot while buffing it before. Maybe ruined some temper but certainly not to any depth that couldn't be removed by sharpening.

I buy the Villagers when I want a user for two reasons: Less cost initially and I don't have to knock the shine off of it myself when I get it with a scotchbrite. I don't like shiny blades for working. They get ugly with work, though some feel all the random scratches make them attractive, I don't. I like to have the random scratches get incorporated into the satin finish over time, just like that look better. I also don't like to have a shiny blade because it is so reflective and tends to make glare issues for me. :)
 
500 degrees or more are required to start making a substantial difference in heat treat, which is easily done if buffing is done without care. Additionally, it is possible to anneal more than just a thin skin when buffing if you are really ham handed about it.

BTW, 500 f is not glowing red ~ you need to be up closer to 1100 and up.
 
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