Using Cardboard Wheels

tim8557

tim8557

Joined
Nov 13, 2004
Messages
878
I've learned an awful lot since joining this forum several months ago. I have especially been interested in all of the information on sharpening. The Sharpmaker is mentioned often and there are many proponents of free handing as well.

What I haven't seen much discussion on is the cardboard wheels on a bench grinder. They sharpen knives on them at the Cincinnati Bass Pro store and seem to do a great job.

One wheel has a silicon carbide grit (220) impregnated on it and that wheel seems to raise the burr edge. The other wheel is just touched up with a white buffing rouge (1200 grit) and finishes the process.

Supposedly, because the wheels are cardboard, no damaging heat is transferred to the blade.

Has anyone had any experiences with this system, pro or con?
 
In the sharpening process you remove metal adjacent to your edge. Even with a perfectly sharp abrasive grit that only cuts out the metal without any rubbing friction you generate heat when you break the bonds that hold the metal lattice together. If you have parts of your abrasive surface that only drag on the surface without appreciable cutting these also generate heat through simple friction. You want to create as little excess heat as possible so you want a sharp open-grit abrasive. You also want the surface of the abrasive to be cool and to draw heat away from your edge.

I would see a cardboard wheel as a very undesireable sharpening tool. It rotates fast so it generates heat fast. When you apply an abrasive compound to the cardboard the grit is carried in a non-abrasive binder so it will do more rubbing with less cutting. The cardboard wheel has low thermal conductivity so it will not draw heat into the wheel and away from the blade edge. The wheel is not very large in diameter so heat going into the wheel surface will not get spread out to reduce the temperature. I would expect the cardboard wheel to overheat your edge a lot. The edge will look good since you are essentially buffing it, but it will be done at the cost of softening the edge. PS. I think this one source of weakness with a lot of factory edges. A much more desireable tool is a belt sander/grinder with a long belt. The long belt will give a much larger surface to spread out the grinding heat. The metal structure of the sander also spreads out the heat. The belts have a dense and sharp abrasive with the binder between the grit and the belt. They waste less heat from friction and do more cutting. They also usually run slower than a grinder wheel. This is a safer tool for sharpening if you use them carefully.

I do remember one place where cardboard wheels are mentioned (without a lot of enthusiasm). This is on a page written by a guy who does a lot of livestock necropsies (cow autopsies). He is willing to buy cheap knives and use them up fast with motorized sharpening systems. He has an interesting point of view and it is well worth reading his notes:
http://gpvec.unl.edu/files/feedlot/sharp1.htm
 
About the heat - it doesn't really matter what the substrate is, if there's enough friction to do anything to the blade, heat IS being generated within the blade and the wheel. That aside, generally cardboard wheels are used to finish an edge, kind of like a motorized strop. For knives that don't need more than a casual touch-up, results can be great. Particularly for convex ground blades.
 
Make no mistake. Those cardboard wheels can ruin temper just like that. They will burn if you stay in one place too long when sharpening. The trick is to keep the blade moving while keeping it straight for the bevel angle you want. They are great so long as you use them right.

Personally I like creating the bevel using a belt sander and then the cardboard wheels are my preferred way of finishing off a new edge of a knife I just made using the silicon oxide wheel after the belt sander, then moving to the polish wheel and then to a leather clad wheel to finish off the new edge.

After that I usually stick to hand sharpening from then on except for my kitchen knives. Otherwise you can watch a good blade disappear pretty darn fast. For my kitchen stuff I usually have like twenty or more at a time and do them twice a year so the wheel is preferred for getting it done in mass. That is why they are popular at shows IMO.

Idealy though if you already have a proper bevel angle and the time there is no need to have to use a wheel and hand sharpening is preferred. At least that is how I see it.

My hand routine for a dull knife consists of four steps. For what it is worth. I know you didn't ask but incase you want to read further here it is.

1) I use a Case carborundum oil stone first. It is two sided and I only use the finer side unless the knife is a really big thick bowie or something like that. This can also make a new bevel pretty quick if need be as even the finer side is quite coarse on the stone I have.
2) I then go to a Moravia Iowa 00 Frictionite barber honing stone/ course side to finish off the edge and take a good bit of the wire off. I say course but it is more like a Washita Arkansas stone.
3) Then I go to the fine side of the same frictionite stone which is equal to the hard arkansas stone to take it to a real fine edge. This process doesn't take long once you get experience under your belt and learn to hold the knife steady and in the same line with each stroke.
4) finally I strop it a few times on a leather strop pushing hard on the blade for five or so strokes on each side using flex cut gold polish compound. Usually after this it will pop hairs off your face or arm with ease on most thin knives and slice paper or fingernails on the bigger ones. I like the finger nail test the best.

Note:You won't find the Moravia stones much anymore but if you do ever see one buy it as they are great stones and make quicker work of the task. Also, you can use diamond paste or green rouge for the compound for stropping instead of flex cuts stuff. I just always have the flex cut compound because of the whittling and carving knives I've bought from them over the years. Seemed like with each new knife I bought I got another bar of that compound so I have a lot of that on hand.

Also, I should point out that you can do away with the carborundum stone and the course side or washita stone and just use and xfine diamond sharpener and then go to the other steps. Either way seems to reach the same end.
 
About a year ago I had an individual bring me an expensive folder that had been ruined by one of these cardboard wheel sharpening setups at a Bass Pro Shop. The blade had been overheated and ruined the temper on about 1/2" of the tip end. He wanted me to try and sharpen it but the tip end of the blade was soft. Just a totally ruined blade.
 
Thanks to all of you for some very erudite and in depth answers. I think I'll stick with the Sharpmaker I recently purchased. Knowing the fact, that I'm never quite satisfied and always need to tinker, I'll be moving onto all of these benchstones everyone talks about.

Thanks again for taking the time to reply.
 
I've tested them. I consider them to be too aggressive and a hassle to maintain. Every now and then you need to glue more carbide particles to the wheel and that's a lot of effort. You should find a system for yourself that doesn't remove so much metal.
 
Every manufacturer that I know uses a belt grinder to sharpen blades. The Japanese, however, are a little more careful about it than others and they may possibly use a finer grit belt. I would assume you would find similar edges on other Japanese made knives like the higher end Cold Steel, SOG and others.
 
I use a 14" cardboard wheel loaded with green compound to strop the wire edge off all the knives that I sharpen. Sharpening is done with a worn out 180 belt.

Pressure and duration are the determining factors in heat build up, keep a light hand on the blade when you are sharpening and the blade will not overheat.

I started using one after finding out that Schrade used cardboard wheels to finish sharpening on all of their products.
 
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