Burned tip on grinder - can it be saved?

I

irona

Joined
May 24, 2016
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So I just got my first belt grinder, made a jig, and now I'm putting the grind on my first serious knife. It's coming out pretty well, except for about 1/2cm of the tip is burned and turned blue. Can the tip be salvaged? I can just grind it off and put a new tip on it, but I prefer the shape it has as is.
 
irona said:
It hasn't been heat treated - does that mean that I should leave it as is or grind it off? Will the blue coloring come off in HT?
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if it hasnt been heat treated then there is no issue, during the heat treat the knife will get alot hotter than the temperature it needed to turn it blue therefore it will eliminate the blue yes.
 
The blue is just on the surface anyways. A slow pass will take it right off. If you think thats bad wait til you see it when it comes out of heat treat! lol
 
As BKT suggests the Temper colors will wear off, but they are indicative of the steel reaching a certain temperature. This, as everyone else mentions, is only imperatively important AFTER the hardening portion of the Heat treating process. After you harden you have to temper the blade. Usually never to the blue color. Thats too hot and will make for a blade that isnt as sharp potentially.
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Typically, and very generally speaking most people stay in the straw/ brown colors when tempering. Say that you got the tip blue After heat treat, then your tip would most likely be back to soft steel again and would musrhoom/deform with any sort of pressure. Only worry about the grinding temps POST heat treat. When grinding after heat treat its best to use fresh belts, go slow, dip in water regularly. Less pressure applied to thinner areas and so on. Hope this helps some!

Gabe



Thats a steel temper color chart, idk how to make it large enough to see. sorry.
 
BKT said:
The blue is just on the surface anyways. A slow pass will take it right off. If you think thats bad wait til you see it when it comes out of heat treat! lol
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That's the thing- I tried grinding the surface off but it's blue throughout the steel.


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It isn't blue throughout. If you continue grinding the tip while it's still really hot, it will stay blue. Dunk it in water, then take a light pass n the grinder again. It will be all cleaned up.

Like the others said, this will not matter once the blade is heat treated. Just make sure not to overheat when grinding after heat treat.

Good luck. Show us pics when you're done.
 
S.Alexander said:
It isn't blue throughout. If you continue grinding the tip while it's still really hot, it will stay blue. Dunk it in water, then take a light pass n the grinder again. It will be all cleaned up.

Like the others said, this will not matter once the blade is heat treated. Just make sure not to overheat when grinding after heat treat.

Good luck. Show us pics when you're done.
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Ok, thanks. Quick question - I'm sending off this blank (1084) to be heat treated, how much does it normally cost for a medium to longer fixed blade? Also how wide should I leave the edge for heat treat so it won't warp?


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.020" - .040" to leave room for decarb grinding after heat treat

Dime thick is a good rule. I do all of my bevels after heat treat so even that is possible...
 
Some of it depends on the geometry of the knife too. I sent a chef knife off to Peters with a .02 edge but the spine was 1/8" and 3" wide and it still warped. If you are making a hunter or something that is thicker throughout the knife it shouldnt be a problem.
 
Daniel Fairly Knives said:
.020" - .040" to leave room for decarb grinding after heat treat

Dime thick is a good rule. I do all of my bevels after heat treat so even that is possible...
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Daniel, that is a common error. A dime is .050" thick. The proper recommendation is "about half a dime's thickness".

In the old days of silver dimes they wore down in use. They would get so worn the images were barely readable. These were called "A thin dime", and are what is referred to in, "As thin as a dime". These were about .035" thick.

Your recommendation of .020-.040" is good.

I send my blades out at 400 grit with a .020" edge for carbon and .010" for stainless.
 
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