Sparks From Power Sharpening Indicate Damage?

M

me2

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Oct 11, 2003
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It came up in the sharpening forum of another discussion site. Anyone have any ideas if it does or doesnt? While it certainly can damage knives, for those who have experience with paper wheels and belt sanders I dont think it does, as long as you're not too heavy handed. I figure any metal damaged by the heat is cut off or winds up in the burr that is cut off.
 
Nah. When grinding a blade, I make lots and lots of sparks before the steel gets hot enough that it would damage the temper.

If the steel gets warm to the touch, dip it. In fact, since you're talking about a thin section, dip it every couple of passes just to be sure. If the steel changes color, then you have problems. :eek:
 
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The discussion centered on the very thin steel at the very edge. Short of some expensive testing, I cant think of any way to prove or disprove the damage. I have also found great freedom in mostly sharpening/reprofiling machetes and small M2 blades. Machetes are soft anyway, and the M2 I use doesnt soften until around 900 degrees. In other words, grind away.
 
me2 said:
The discussion centered on the very thin steel at the very edge.
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I understand. If it gets overheated, you'll know, no expensive testing required. It will turn pretty colors and won't keep an edge worth a damn. As you said, grind away.
 
when working up a burr on a belt sander or paper abrasive wheel you are going to generate a little heat if you are running at a high rpm. thats why i run my wheels and belt sander at a lower speed. on carbon steel blades i do get sparks when using the abrasive wheel but thats to be expected but i'm using light pressure. i'm always checking the blade for excess heat. you can get a blade hotter rinsing it off in hot tap water than you can by making a few passes on the paper wheel to work up a burr. take a cheap knife and do some experimenting. you might be suprised at how much heat a blade can take and not get damaged.
 
richard j said:
when working up a burr on a belt sander or paper abrasive wheel you are going to generate a little heat if you are running at a high rpm. thats why i run my wheels and belt sander at a lower speed. on carbon steel blades i do get sparks when using the abrasive wheel but thats to be expected but i'm using light pressure. i'm always checking the blade for excess heat. you can get a blade hotter rinsing it off in hot tap water than you can by making a few passes on the paper wheel to work up a burr. take a cheap knife and do some experimenting. you might be suprised at how much heat a blade can take and not get damaged.
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*Goes and ruins a blade* :D:D

As long as you dip the blade in water when you feel any heat, you'll usually be fine, when working on fast belt sanders, the biggest problem IMO is a really thin and narrow tip, I've burnt my fair share of tips when I first started using a belt sander.
 
Roger999 said:
... the biggest problem IMO is a really thin and narrow tip, I've burnt my fair share of tips when I first started using a belt sander.
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That's true. Being such a small section of steel, the tip will obviously heat up faster.

As Richard and Roger mentioned, very light pressure and controlling heat is the key. For sharpening, unless you or your customer let the knife get really badly dull, it shouldn't take much pressure regardless if you're using a light-speed grinder or hand stones. It's not rocket-science, folks. :)
 
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