I have seen the light, and it's a belt sander.

lewdog said:
I cherish have fingers that number in the double digits, so I'm right there with you all on edge trailing.
Regarding the angle guide--I know I can estimate. That ignores my knifenut, OCD nature, though. I must have total control! :cool:
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Since the belt wraps aroung the edge based on belt tension, blade pressure, where exactly the edge is with respect to the idler at the top or the platen at the bottom, AND the angle you think you're holding so you'll never know what you end up with, it just might cure those OCD issues. :D

The FORCE will guide you... ;)
 
Bill DeShivs said:
Edge-leading can be done, but it is dangerous.
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Throwing the knife? I have done it that way for years, produces far less burr, clean right off the belt. No finishing required, I use 80 grit AO for slicers. Finish that with some like D2 and you cut cardboard, ropes, fabrics, etc. for an insane amount of time. 2000+ slices through 3/8" hemp with the force still hovering around 20 lbs.

-Cliff
 
Lewdog,

My answer isn't as cool as Jerry's, but my first split-the-hair-on-my-arms edges came from using a 1x30 belt sander with an 80 grit belt, 15 micron SiC belt, and a leather belt loaded with 1/2 micron diamond compound. Three belts, a few minutes, and sharper edges than I was getting with an EdgePro Apex system and a ton of aftermarket goodies.

If you want a longer lasting edge of the same level of sharpness, use more belts between the 80 grit and 15 micron SiC belt (which starts its life as a 1000 grit belt and gets finer with each use - the magic and downfall of SiC) or else you'll just be polishing the teeth left by the 80 grit belt (or so it behaved).
 
Cliff, you're special. My advice only applies to normal people. Digging the edge of a sharp knife into a moving leather belt is a bad idea. Less burr also happens when you round the edge because you pressed it into the belt causing the belt to push up in front of it. That's one of the reasons I taper tangs with the butt end trailing. Otherwise you round the otherwise square ends.

Using 80 grit belts to finish an edge is also not a good choice IMHO. I've never used an 80 grit belt on an edge, even with a large knife that is dead dull. On a previously sharpened knife you should never need anything more coarse than 220 grit.
 
Thanks for your posts on this, Jerry. I've enjoyed using my HF sander. Great for when you want to remove some metal fast, and the 15micron/9micron/leather belts are well worth the investment. Makes for a very quick touch up system while doing samurai hedge trimming, bushwacking, or hacking at roots in the yard! Works great to keep a good edge on the shovels and mower blades, too.
 
Without really thinking about it, I ordered the 1200 grit belt and the 15u belt from Lee Valley (among others). My assumption was that I would use the 15u belt after the 1200 grit, then on to the strop. But, it was mentioned that the 15u belt is the equivalent of 1000 grit, which would be a step backward. Is that right? So, should I use the 15u before the 1200? Does the 15u belt play some different role that I'm not seeing?
 
At first the 15 micron belt will be rougher than the 9 micron belt. The 9 micron belt is made with aluminum oxide and its abrasives will stay about the same until the belt finally stops cutting. The 15 micron belt is made of silicon carbide and will rapidly break down to a finer finish with each and every use. So for your first two or three knives, it could be a step back, but it will a step forward from there on out.
 
Jerry Hossom said:
Digging the edge of a sharp knife into a moving leather belt is a bad idea.
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Probably, but I don't use leather belts, as noted I don't finish polish on a belt sander. I went over this before, it is wasteful and removes far too much metal. That is just simple math, high school level.

Less burr also happens when you round the edge because you pressed it into the belt causing the belt to push up in front of it.
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This doesn't happen either, checked it under mag. Lee describes the actual reason in his book on sharpening, he leaves out a few factors, but it is all just simple physics.

Using 80 grit belts to finish an edge is also not a good choice IMHO. I've never used an 80 grit belt on an edge, even with a large knife that is dead dull. On a previously sharpened knife you should never need anything more coarse than 220 grit.
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Such knives shave above the arm and can slice through 3/8" hemp with about 7-9 lbs on a two inch draw, I have done 2000+ cuts with a D2 blade and it was still at aboit 20 lbs on a two inch draw. 80 grit on something like 420J2 would easily outlast something like 154CM at a much higher polish. Not even a contest. Swaim documented this in detail over ten years ago. Some knifemakers are aware of it as well, Dozier for example leaves his knives with very rough edges for the same purpose.

-Cliff
 
Cliff
I disagree that an 80 grit belt is good for sharpening. I seldom use 80 grit to begin grinding bevels on a blade! 80 grit should, theoretically, leave an edge with serrations of 80 per inch. Advising people to sharpen edge-up on a belt sander is irresponsible.
I would think that sharpening on an 80 grit belt does remove far too much metal! I start sharpening with 400 grit.
Bill
 
When I first got my little belt sander I tried sharpening with an 80 grit belt and did it edge up. That will quickly turn your knife into a chisel ground edge. It is much better to use belts with much higher grits than that to sharpen. If you want a real coarse finished edge like that best to put it on without power. I also find it much easier to sharpen edge down, I’ve done it both ways.
 
Cliff, let me ask this. How many thousands of knives have you sharpened, all of which were to be used by other people who would judge you by the results?
 
Here's a quote by Cliff from a different thread where he was defending edge leading sharpening (and responding to the notion of the edge catching) with a belt sander (note the ironic misspelling of "severely"):

"I have never had this happen. I am not doubting that it could, but either it is severly unlikely or I am really lucky. I don't actually consider it that dangerous compared to things like table saws, entire family is carpenters and lots of stubby fingers around. It is also way more dangerous to use larger knives than sharpen them anyway and in general I am far more likely to get killed in a car accident anyway."

Darwin, anyone?

Sorry, Cliff, couldn't resist. :p
 
Yve spehlt guddir.

There are easier ways to get hurt, but that doesn't make edge-leading sharpening safe per se and it won't do much if you're using a leather or mylar belt as Jerry suggests. On standard belts (cloth-backing and resin-bound) and Trizact belts, it doesn't seem to matter - both edge-leading and edge-trailing exert strong downward forces on the blade with the coarseness of the abrasive amplifying or attenuating its intensity (15 micron SiC feels like holding the knife under a hair-dryer; 40 grit Zircon belt can be felt the next day).
 
Just my own anecdotal experience: I've found 80 grit cloth backed belt, edge leading, put a surprisingly keen edge on carbon steel blades. Moving up to finer grits only made the grind prettier, not necessarily sharper.

The only leather belt I've ever seen was a stropping belt. Do they make leather sanding belts? Is there an advantage?
 
shecky said:
Do they make leather sanding belts? Is there an advantage?
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They do! And the advantage is speed! A leather belt loaded with buffing compound will strop much faster than a human hand which allows you to perform several more passes at the same angle than with your hand-strop which also helps remove fatigue and pilot error from the equation.
 
When sharpening edge-up, the edge can actually catch on the belt-severing it. If the knife is not thrown, the belt can still hit you in the eye, or if the edge of a belt hits you it can inflict a nasty cut.
Bill
 
Very true. The edge can also inflict nasty cuts when it's still on the sander and you're polishing riverstones instead of sharpening. And that's unfair!
 
The last time I used a 3M microfilm belt, I touched the side of the belt with the back of my left hand. Just a touch, hardly felt it. Next thing I know I'm squirting blood halfway across the shop. I had to wrap it in three shop towels to finally restrain the bleeding, then drove to the ER with my hand elevated out the window of the car, drawing some considerable attention from other drivers. Bloody rags have that effect I guess.

Anyway, it took three stitches to sew shut the wound. Seems those are arteries on the back of your hand. That's the high pressure side of the pump and accounts for the impressive squirts and equally impressive quantity of blood on the shop floor.

Edge trailing, watch the edge of the belt. It bites. :)

Oh yeah, knifemakers aren't supposed to admit these things. Pretend you didn't hear it from me. Say it was Cliff! :D
 
thombrogan said:
They do! And the advantage is speed! A leather belt loaded with buffing compound will strop much faster than a human hand which allows you to perform several more passes at the same angle than with your hand-strop which also helps remove fatigue and pilot error from the equation.
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I was aware of leather stropping belts. I was wondering about leather sanding belts, because Bill DeShivs warned about edge-leading sharpening, who subsequently was backed up by Jerry Hossom, who specifiically warned about edge-leading on leather belts. Neither mentioned the use of a leather belt for stropping.

It would never occur to me to strop a knife, edge-leading, with a leather belt, especially on a power tool. But this is different than grinding a blade edge-leading.
 
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