Sharpening with belt sander

I'll have to disagree that a 15 degree edge is universally too low. I have other machetes that will hold this edge angle without damage, and they are longer and/or heavier and hit much harder than the Barong. I've also seen and talked with people who have used axes all their lives and use edges thinner than 15 degrees. I'd agree that fine grits generate less heat, but the reference was done on 1000 grit paper and generated temperatures over 2000 degrees, by hand. I don't think it makes a difference what grit isused with respect to the last microns of the edge.

It's odd that you and many others use such a variety of grits to sharpen on a belt sander. You would think a narrower range of grits would come out as better than others. I typically use a VERY worn 180 grit belt. I've been using it for 4 years or so now. I've seen people here and other forums use everything from 80 to 1200 grit, which I used for a while until it was damaged during an acid spill. I also power strop with a Surgisharp belt with white compound.
 
Yup it is a little wierd that we all use different combos of belts. I bought a wide range of grit belts and truthfully have only ever used the 320 1 or 2 times, the 600 every time, and the leather with green compound to finish. When I had my 1x30 I used alot of belts at the lower grits but really didn't use that belt grinder as a sharpener. Didn't even have leather for it. It was mainly a reprofiler. Id agree 15 degrees per side should be fine to chop tipical wood with.
 
Interesting, but wouldn't steel type and heat treatment also play a part in whether or not an edge angle is too low?

In any case, I'm more interested in knowing whether or not Roman actually observed any damage to the heat treatment itself from the hand sharpening, and not just the temperature. As I understand it, even at austenizing temperatures the steel must be held at that temperature for a while in order to undergo a change to austenite. And of course, the very fact that holding a blade on the same spot for too long would show obvious signs of a damaged temper in the form of a color change in the metal should suggest that the preventative measure, that is, moving the blade quickly off the spot or quenching it, helps to minimize or even avoid damage by dissipating the heat. I'd like to think that 2000 degrees of heat generating from a swipe across 1000 grit sandpaper would be dissipated pretty damn fast if I can't even feel the heat on my fingers.

Again, I'd like to think that this isn't as big an issue as it is made to sound, otherwise I'd have to worry about the temper every time I cut cardboard. And given that my Para2 in S90V went 3 months of cardboard cutting without needing to be sharpened, I have some doubts as to whether this would be the case.
 
I don't think that the heat generated by properly done powered sharpening of a knife would be a significant factor. Certain types of usage can generate ludicrous amounts of heat(I once nearly burned myself on the blade I had been using to cut rope) and since it can be assumed that the edge would be experiencing a high percentage of the friction involved it must get really hot for extremely short periods of time.
 
I personally use a belt grinder and a whole variety of belts. It comes down to skill and technique just as much as any other method of sharpening. It is fast and you can take it as far as you want. With the proper belts and technique you can even put a mirror polished edge on a knife in minutes. Follow the same tricks as with anything else consistent angle and even pressure will get you pretty far. Just you have to be careful not get get a blade hot.
 
cap'njake said:
I personally use a belt grinder and a whole variety of belts. It comes down to skill and technique just as much as any other method of sharpening. It is fast and you can take it as far as you want. With the proper belts and technique you can even put a mirror polished edge on a knife in minutes. Follow the same tricks as with anything else consistent angle and even pressure will get you pretty far. Just you have to be careful not get get a blade hot.
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Agreed!
The ones saying stay away from a belt sander either have not used one, used one and didn't know what they were doing and didn't take the time to learn (and it doesn't take much time), or just plain have a block against anything other than old school stone sharpening. How do you think most factory knives are sharpened? Not saying they are as sharp as they can get, but they aren't ruined by the belt.

If you don't like any kind of power sharpening, don't use it, but don't make up excuses to keep others from trying it. If you have unbiased proof that intelligent power sharpening burns edges... let's see it.
 
I have been to some gun shows where the guys using belt grinders are throwing sparks like mad from start to finish. That's not really good. When I am sharpening on a grinder I usually don't throw many sparks. Depends on what the steel is some tho. Some steels with just throw lots of sparks and some don't throw much. And as for protecting against heat you need to hold the knife with your barehands. Keep your fingers as close to the edge as you can to feel any heat buildup. Some people act like if the steel even gets warm it ruins the temper... well if that is the case using a knife to cut open a hot potato will ruin the temper. To ruin temper the steel needs to get over the temperature it was tempered at. Usually that is around 400 degrees. If the steel gets to those temperatures it will burn your hands obviously. So if you do a pass, dunk the knife, check the edge, and then do another pass you shouldn't get the blade even very warm let along hot enough to ruin the temper. Unless you are using way too much pressure
 
cap'njake said:
I have been to some gun shows where the guys using belt grinders are throwing sparks like mad from start to finish. That's not really good. When I am sharpening on a grinder I usually don't throw many sparks. Depends on what the steel is some tho. Some steels with just throw lots of sparks and some don't throw much. And as for protecting against heat you need to hold the knife with your barehands. Keep your fingers as close to the edge as you can to feel any heat buildup. Some people act like if the steel even gets warm it ruins the temper... well if that is the case using a knife to cut open a hot potato will ruin the temper. To ruin temper the steel needs to get over the temperature it was tempered at. Usually that is around 400 degrees. If the steel gets to those temperatures it will burn your hands obviously. So if you do a pass, dunk the knife, check the edge, and then do another pass you shouldn't get the blade even very warm let along hot enough to ruin the temper. Unless you are using way too much pressure
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Carbon steels throw sparks. Stainless steels barely will, if at all.

Remember that the very edge of a knife is as thin as foil. It takes a split second for that steel to heat up beyond 400° and the rest of the knife can still feel cool. So the trick of feeling for blade warmth doesn't necessarily always apply. The trick is more to use fresh belts, a light touch, and long, rapid passes so you don't stay in one spot for long. :)
 
There bust be a reason that knifemakers finish either by hand (even if it is only a microbevel) or use a watercooled slow speed belt.
 
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