Sharpening with belt sander? Destroying temper/heat treating on edge?

S

SPERRON

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I have a new (my boss has a new) belt sander at work that I have experimented with for sharpening a few knives that I don't really care much about. With a fine belt it puts a shaving edge on in no time. Sometimes the edge is hot to the touch right after sharpening (unlike hand sharpening).

I usually use a Lansky diamond clamp thing that I know doesn't affect heat treating. My question is: Have I just screwed up the heat treating in any way by letting the edge get very warm?

I want to use it for good knives but fear ruining good steel on it.
 
it is possible you have affected the heat treat.

those who use belt sanders for sharpening or mods typically say to run it slow and use a slack belt. if it gets too hot to touch, let it cool before starting again.
 
If it gets hot enough to affect the heat treat, you will see a change in color.

Use light pressure, and don't linger in one spot. Also keep a bucket of water handy, and cool the blade after each pass.
 
Sherron,
I wouldn't. The ONLY grinder or belt machine I'd remotely consider applying a good knife to is those with a water bath. I've worked in machine shops and as a gunsmith off and on for 50 plus years. I can attest to the fact that machine grinders/sharpeners/belt sanders/etc. have ruined many a good knife, tool, gunpart, etc. Been there, done that, and learned the hard way. IMO any excessive heating (beyond what a knife or cutting tool would encounter in normal use can degrade the temper and thus the edge holding ability.
 
I sharpen most of knives on a 600-800 grit slack belt and get a very good edge. That's the way I was taught by Gill Hibben who sharpens all of his knifes that way. As said before, just go slow with light pressure. When the blade starts to feel warm, cool it down.
 
It's an acquired skill, definitely. I would go to rummage sales, and get cheap kitchen knives, use them for practice. It's quite easy to ruin the temper if you don't pay attention. So I've heard. ;)
 
a knife can safely be sharpened on a belt sander with plenty of practice and the proper grit belts without the worry of burning a good blade. slow is always the way to go when it comes to a belt sander. mine runs slow enough that i can see the seam go by. going slow makes it hard to burn a blade unless you use a lot of pressure. a blade can take some heat like when rinsing under hot water.
 
Richard, what brand do you use? Is the speed adjustable? Mine is too fast, and I'm going to look for after Christmas sales. Thanks!
 
i'll pm you the info. i'm thinking of making them, its a simple design and you're not limited to a certain length 2" belt.
 
I always bare hand sharpen if I am using my belt sander. Mine is not adjustable for either belt speed or tension. I always stop to let blade cool BEFORE it gets too hot to handle.
 
Isn't that how the factories sharpen them before they let them out the door?

I've never ruined the temper using a belt sander, but I always watched the heat buildup and either quenched it or stopped before getting anywhere near tempering temps.

I like the idea above of using some cheap kitchen knives to learn how much is too much.
 
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