How hot can 5160 get without losing the heat treatment?

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anacondaforge

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Nov 28, 2016
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I made my first knife over a year ago, and at the time I only had a cheap Harbor Freight 1x30 grinder. I was able to do a decent job grinding, but it still turned out to be obviously the work of a rookie. I have since purchased a used 2x48 Kalamazoo grinder that I got an unbelievable deal ($30) on from a guy about 100 miles away who was clearing out his shop. I've been too busy due to starting a new career that has me travel constantly to even use it, but I finally have a few days off and I ordered a bunch of belts for the "new" grinder. I'm wanting to revisit that first knife because I made it as a gift for a relative, and it just doesn't cut as cleanly as it should. I'm sure that if I totally reworked the bevels it would be a much more functional knife. My question though is how hot can it get before I have to worry about losing the hardness? It's got way too much steel near the edge, and I'm afraid of overheating it as I hog away all that material. What I'm wanting to know is what temperature range is the "danger zone" for losing the hardness. It's made of 5160. I've heard from different people that that temperature could be anywhere from 200-1600 F, but I'm wondering if anyone can give a more precise number.
 
General rule of thumb is if it’s to hot to to handle comfortably then dip it. But the edge being thinner builds up heat much faster. I normaly grind with my thumb putting pressure on the edge Bevels. This keeps me clued in on the temp of the blade.
 
JTknives said:
General rule of thumb is if it’s to hot to to handle comfortably then dip it. But the edge being thinner builds up heat much faster. I normaly grind with my thumb putting pressure on the edge Bevels. This keeps me clued in on the temp of the blade.
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I've always wondered...is the blade too hot if a bladesmith's hand can't hold it comfortably or if a normal joe can't hold it comfortably anymore. Because I think that could be quite a difference.
 
The issue is that while the blade may rarely get over 200°F, the edge can climb to 600°F is a fraction of a second. Everyone has burned a tip while grinding even though the blade is barely warm. Dipping every pass both lubricates the blade and wets the belt for a few seconds of wet grinding.

The real solution is making a wet grinder. If the belt is properly wet by a spray or mist, it is hard to burn an edge. Grinding is faster and more efficient, also.
 
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