sandpaper re-profiling?

E

englishteacher

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Oct 24, 2002
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I'm trying to put together sharpening info I've been reading here. I get a decent edge with my Sharpmaker, but I think it could be better, and on thicker knives I have to tip the blade slightly to even get to the edge, which seems to be the main limitation of the Sharpmaker. Reprofiling is the answer. So I'd like to reprofile to the the 30 degree setting and use the 40 degree for the secondary bevel, the actual cutting edge. Is this right?

Someone posted that I could use sandpaper attached to the rods to reprofile. How would I attach it? What grit sandpaper? Will it work fast this way? I do have a Lansky system as well, but it doesn't seem all that fast, either, and the Sharpmaker is so much easier to use.

Help appreciated.
 
The expensive way I do fast reprofiling is with the x-coarse Edge Pro stone, or an x-coarse DMT hone. The cheap way is to get low-grit paper (I think I'm currently using some kind of wet-dry paper), anything under 150 will cut fast, the lower the faster. You can use the paper however you'd like, e.g., you can wrap it around the Spyderco stones so you can use your sharpmaker's angles to reprofile.

Regarding angles, I suggest that with a good steel, 20 degrees per side is way too obtuse. You're giving up a whole lot of performance for no good reason. I say sharpen the whole thing at 15 degrees per side (Sharpmaker 30-degree slots). Then when you're done, take a few light swipes in the 40-degree slots just to be sure you're rid of the burr. There's very little reason to do a full sharpening at 40 degrees, unless you already know that your knife chips out or indents badly at 30 degrees ... in which case, I'd suggest the answer is to get a better knife, not to go with a thicker edge ( 1/2 :) on that -- obviously, if you're using the knife edge really really hard, you might need the 40 degree angles, but for a folder with good steel, 40 degrees is a sacrifice of significant cutting performance for no good reason).

Joe
 
I would use 120 grit or coarser Wet or Dry paper. Cut it crosswise into 8"x2" strips. Lay a paper strip abrasive-side down on a counter and lay a Sharpmaker rod lengthwise down the middle of the paper. Fold the paper along one edge of the rod and crease it. Holding the fold against the rod crease the paper along the opposite edge of the rod. Lift the rod out and make the creases sharper by folding them each flat in turn (only do this once since you don't want to break the paper).

To attach the paper use several binder clips from an office supply store. The paper is folded over the rod along the creases and the free ends of the paper are clipped using the binder clips. You can cover two rods if you get enough binder clips or you can work one side at a time and just use one rod.
 
So I've got a lot of work to do. Do you just wrap the sandpaper and hold it with one hand? Do you do 20/20, or just one edge at a time?

Why does the Sharpmaker feature the 40 degree if it's not optimum?
 
Originally posted by englishteacher
Why does the Sharpmaker feature the 40 degree if it's not optimum?
Click to expand...

Doing either way, alternating or one side at a time, will work well. Get ready to do a lot more than 20 per side if you're removing a lot of metal to reprofile.

I'm not sure why 40 degrees was chosen, but there are two good things about it:

  1. Many knife manufacturers suggest stone sharpening at 23-25 degrees per side, which would be 46-50 included degrees. The Sharpmaker is a little to a lot better at 40 degrees (20 per side)
  2. Most Spyderco knives come from the factory with about a 30 degree angle for the edge. 40 degrees allows for a micro-bevel that is a lot easier to sharpen.
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    The mind-warping part about angle settings is that sharpness and cutting ability are related, but not synonymous. You can have a .25" thick blade with a scary sharp edge at a 44 degree angle and a .09" thick blade with an almost-shaving sharp edge at a 24 degree angle will cut circles around it. But then, with two blades of the same thickness sharpened at the same angle, the sharper blade will then be the better cutter.

    Well, that's my $.0125 on it.
 
Originally posted by englishteacher
So I've got a lot of work to do. Do you just wrap the sandpaper and hold it with one hand? Do you do 20/20, or just one edge at a time?

Why does the Sharpmaker feature the 40 degree if it's not optimum?
Click to expand...

I just hold the paper with one hand, but Jeff's binder clip idea sounds like it'd work great.

I personally think of 40 degrees as a reasonable angle for the knife-world version of the hoi polloi :) But if you've bothered to hunt down bladeforums, that already means you care more about your knife's performance than most people. 30 degrees per side is harder to do, requires removing more metal, and more skillful removeal of the burr. But if you care about how well your knife cuts, the rewards are more than worth the little bit of extra effort.

Joe
 
The diamonds work more reliably for serrations and last longer than sandpaper, but 80 grit aluminum oxide will readily outcut 400 industrial diamonds.
 
Things that I didn't say, but I was thinking when I wrote my previous post. I would slip the rod into its normal 15-degree ("30 degree label) slot. I would have the rod rotated so that you are sharpening on the flat side of the rod, not the edge. You would wear through the paper very fast if you used the edge. Clip the paper onto the rod such that the paper goes down to the base, but not into the base. You can trim the paper to match the length of the rod if you want, but it should not be important.

I would sharpen one side of the blade until I just start to feel a burr on the side of the edge away from the hone. It might be handy to count strokes. I'm expecting something like 100 strokes. Then sharpen the other side until you get a burr on pretty much the whole length of the blade. I would expect that to be around the same number of strokes as you did on your first side. At this point you will go to alternating sides. You are going to get rid of the burr by working alternate sides lightly at about 2x the angle that you have been using. Switch the rod (or rods) to the 20-degree setting (keep the paper on the rod). Lightly hone with the blade tilted away from the hone slightly to get an angle higher than the 20-degrees you would get if you held the blade vertical. Do this about 5 light strokes per side. You want to remove the burr, but you don't want to make your edge more obtuse.

You are now done reprofiling. Sharpen the blade without the paper according to the nominal Spyderco directions. I would start with the edges of the medium-fine rods. You want to work out any scratches left by the paper. Alternately you could get some finer Wet or Dry paper and set it up like you did for the 120 grit. Do a little light honing, say 15 strokes per side on each grit. You might use 220 grit and 400 grit. Another approach is to lay some 400 to 600 grit paper on a mouse pad and do a little stropping to get rid of the scratches. This is a little risky since you are likely to marr the finish of more of the side of your blade than you intend.

For all of the above you might want to try an old kitchen knife as your first experiment. This reduces the chance that you will marr your blade or make crooked bevels.

The diamond rods would certainly do reprofiling for you but they are really expensive. I think they list around $80 for a pair.
 
The reason for 20-22 degrees being almost universally recommended is probably because it is trivial to judge by eye as you can get it from halving 90 twice, and judging a perpendicular can be done to high precision.

-Cliff
 
There's a simple solution to your problem. Get an extra-course diamond hone for your Lanskey for only ~$15. Then you can easily and rapidly hog-down your thick blades to a nice uniform cutting bevel that is easily maintained by your Sharpmaker. Works great for me. It's got to be easier than using paper. Saves over $100 versus the Edgepro.
 
I did this by hand recently on a chipped out Fallniven kitchen knife.

I started with 80 grit with the knife held out over the edge of a counter (long-ways to give it the most support) and used a rubber sandpaper holder you can buy at Home Depot for ~$5. I stepped through a bunch of grits to 2000. It wasn't as fast or precise as it would have been with an EdgePro or Tormeek, but it was an entertaining way to spend an evening.
 
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