Belt Sander Sharpening Problems/Solutions

Bill DeShivs said:
If you are using a rubber "belt eraser" on your Trizact belt, that's where your black marks are coming from. The belt is too fine for the rubber to work and it melts and builds up in/on the belt. When you use the belt, it re-melts and deposits on the steel.
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Leave it to Bill to know EXACTLY what the problem was... kudos my friend.
 
Pressure is really your enemy regardless of the sharpening media being used. Its human nature to think that more pressure will make something work faster. Thats really not the case. Like in auto racing sometimes you have to slow down to go faster. One has to let the tool do the work so you can concentrate on technique. Something even after many years I still have to remind myself of.

So if your rounding off tips or whatever use less pressure and lift the tip off in the middle of the belt.

The media is the tool. Whatever your using to drive that tool, be it a belt grinder or simply your hands and arms, is the machine making the tool work.

Trizact belts have a place but I've never been fond of them in the sharpening arena. Of all that I've used up to 16 micron I like the 45 micron the most. I get better results using a 600 SC belt in that beyond 220 grit range. If I decide to go higher I use a linen belts with CBN emulsions to 8 micron then finish with a leather belt with 4 micron CBN. I normally go the leather belt after the 600 SC belt. A great edge for most common knives.
 
Pj you've got it right. I have that same problem having to remind myself sometimes more pressure doesn't equal more speed. Myself the only belts I've used beyond 120 grit have either been trizact or the 3m micron belts. Weren't trizact belts made specifically for sharpening? The gators I thought were more for grinding. I've been meaning to pick up a few of the black SC belts supergrit sells on my next belt order. Are they cloth backed? And where do you get linen belts? I figured for anything besides polishing they'd round an edge as they don't have the grit to stiffen the belt and I figured they'd deflect a lot. Not to mention compounds are extremely expensive compared to a belt. That's why I only use a compound on the final polish/deburr step
 
The SC belts from Supergrit are what I use. They have a resin impregnated cloth backing. I think its a Y backing. I order from them more than other vendors. The trizact stuff is an engineered abrasive. If they were designed for sharpening I couldn't say. I doubt it.

The linen belts you can get from the Klingspor Woodworking site. They are very economical used with CBN and diamond. I use CBN all the time. Up front there is an investment but I'm going on a year on the 16 and 8 micron and have maybe used 1/4 to 1/3 of a two ounce bottle. I just started using the four micron on leather so I'm still experimenting. Bar compounds, except diamond bars, are a thing of the past for me. I would think a two ounce bottle has a good year in it if you sharpen as many items as I do. Probably longer. Leather belts can last for years.
 
I use the 3M S/C Mylar belts that Fred mentioned for my final pasts and I'm very happy with the results. I get them from Scott at trugrit.com

Don't care for leather belts. in the shop or bedroom!;)

To deburr I use a hard sisal buffing wheel loaded with Green Chrome compound. Sharp belts is the key, after i have used about half the grit on any of the Ceramic or O/A belts then then go into the profiling or handle sculpting pile.

I have a small bucket of water and dip the blades before each pass. Also I work tip up, with the belt heading into the edge.

I never bring the tip over more than about 1/3rd of the 2" belt
 
I've actually noticed using more pressure DOES reprofile much faster. Maybe because I only use the slack portion? I never use much pressure with actual knives, but machetes/axes need the pressure or I will literally be standing there forever. Many more sparks fly with more pressure. Maybe because the terminating apex angle is increased?

I think I prefer the finish of the paper thin 9 micron aluminum oxide grinding belts over the 6 micron trizact. It's more mirrored.

I've also just given up on power stropping, I seem to get better results from a hand strop.

I remember reading all the hype about belt sanders needing no skill to use properly, boy was that a bunch of BS! There's definitely a learning curve. A lot of times I thought about giving up and going back to hand sharpening.

It's not like I was bad at hand sharpening, I just didn't like spending forever reprofiling knives by hand.
 
Obviously more pressure does equal faster grinding. What I don't think you're realizing is using more pressure on the slack portion is increasing your effective angle. By a lot. As the belt deflects it curves around the blade giving a much stronger convex. Also much less sharp. It can get up into the 60+ degrees inclusive which is much too thick on anything but a concrete chisel. If you prefer the 9 mic edge to the a6 edge then use the 9u. They're your edges use what you like. I believe it's because the trizact works like a waterstone as it is always releasing fresh abrasive so you're getting less of a burnishing effect and more of a true 6 mic scratch pattern. Which isn't fine enough to be a mirror. On power stropping for me at least it's how I soften and remove that last little bit of burr. I've yet to find anything else that will do it. That may change as I'm ordering a slotted paper wheel. Because I use edge trailing there is no way to not have a burr as any pass no matter how light will just make a new one. And like you that's why I started with this method. By hand just takes too long. And I've yet to encounter a knife that didn't need some thinning. And yes there's definitely a learning curve like anything else. I've been at it for 5+ years and I still learn something almost every time I turn it on
 
Yes, the terminating angle is pretty high, but the edge is pretty thin behind the terminating apex. It keeps the edge strong and and still cuts like crazy, so it's a good edge for machetes/axes IMO. All I know is I'm happy that I've finally figured out how to get tree-topping edges off of it much more consistently through practice and the help of all the good people on this forum :)
 
I would learn more from pjwoolw and his approach to CBN. I mostly sharpen kitchen knives where a 2k grit plays nice with the fibers in meat and veggies.
Pressure is dictated by the stiffness of the belt. I'm always looking for something better, but for what I do, a Zirc belt followed by Trizacts seem to be the best. Heavy pressure on the Zircs and teach yourself through out the finishing belts.
I sharpen several hundred knives a week. As much as 150-170 in one day.
 
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