Grinding and shaping bevels

[Steve Friedman]

The only issue with the trizact belts is that if there is a hard platen under them, they will burn steel very quickly - especially in something with the belt speed of a viel grinder. If there isn't a hard platen under them, then you'll get a convex edge. I've actually never used another tool that made the edge so hot so fast as a trizact belt with a hard platen under the belt

I actually like coarse grit belts on a belt grinder better if grinding is the purpose. The trizact belts work well if you are willing to tolerate the convex bevel, and are great for sharpening stuff like a knife that gets abused, or turning tools where the heat doesn't matter much.

David, I agree completely. I bought some Trizact belts a while ago because they were supposed to be cooler, but experienced the same thing you did - quick and severe heat build up. Using the belt grinder above the platen is fine for adzes, axes, and other roughing tools with rounded profiles. It's the perfect tool for sharpening kitchen knives. I stopped using it for plane and chisel blades because I find that I cause much less harm with good old sandpaper on granite.

Steve

[Tom M King]

After spending many hours with water grinders, the CBN wheel does the work at least 50 times faster, and you have to try to burn something. The hard part is learning how fast it cuts without taking too much off of something. If you get one, practice with something that it doesn't matter on.

[Mike Holbrook]

What is a CBN wheel?

[Alan Schwabacher]

CBN is cubic boron nitride. It has the same structure as diamond, except that all the carbon atoms have been traded in for boron or nitrogen. The consequence is that it's very slightly softer than diamond, but in contrast to diamond it does not dissolve in iron. That's helpful for grinding steel. Unfortunately, CBN is not cheap.

[Derek Cohen]

I'm curious to know who has used a 10" CBN on a Tormek. My Tormek wheel is wearing down. About 8 1/2" now. Still has a good bit of life, but I prefer the shallow hollow. I gather that there is a 10" CBN wheel available for the Tormek.

How does the slower speed impact on the the way the CBN wheel cuts - or is this an advantage? Obviously it will no longer be used in wet mode.

Regards from Perth

Derek

[David Weaver]

Derek, I don't know if there is one for the tormek. They are (or were at least last year) in the range of $150-200 for a 6 or 8 inch grinder. The virtue of the CBN is that it can work at speed on steel - unlike diamond, and it may not be as long lasting or nearly as effective at low speed.

If you were to get one, I think you'd get it for your 8" grinder instead.

[Chris Fournier]

I can't imagine needing CBN to sharpen woodworking tools that are not carbide. I use CBN in my metal shop to sharpen carbide tooling using it for "mere woodorking tool steel" would be slow and a waste of money and time. Up to HSS you simply can't beat AO. A decent tool rest, bench grinder, and a 46 grit AO wheel. Some practice and you won't see blue steel in your shop. I rarely use water to quench when I am using my bench grinder on woodoworking tools, with the right touch it is simply not needed.

Don't give up on conventional bench grinding, take the time to develop the right touch, you'll succeed and wonder what all of the fuss was about. CBN is an expensive and unecessary solution to a non-existant problem in the average WWKg shop.

[Ruperto Mendiones]

Square edge on Tormek. I struggled with the old tormek square edge jig. It had clamping screws on either side of the tool. If one was tighter than the other the edge would skew out of square. The newer (circa 2010) Improved Square Edge jig, SE76 made it MUCH easier to produce a square edge.

Another machine, the lapsharp uses trizact abrasive films on aluminum discs to produce a flat surface. Great for reconditioning chisel backs but for me I prefer hollow ground edges rather than flat bevels.

[Tom M King]

Nothing slow about CBN on woodworking edges. Maybe 3 seconds to bevel a chisel. Not to mention, nothing to balance, true, account for diameter changing, or grinding wheel dust. I still use a regular grinder for rough stuff, like mower blades. No more wet grinder, and the belt grinder only gets used on golf club work.

Probably not worth the cost for a hobbyist, but if time is money, it saves a LOT of time.

[Chris Fournier]

Belt sanders are hot. Check out some metal fabricating forums where heating the metal is not good, belt sanders run hot reduction for reduction vs other methods. I have a belt sander and it must be used very carefully when sharpening high carbon steel - it requires more touch than a properly set up bench grinder.

[Mike Holbrook]

I have been working drawknife bevels on my Tormek. I think the problem I have had more recently has to do with the convex bevels that came on them or I created sharpening by hand without a guide or clamping system. The belt sander also makes a convex bevel if one does not press the tool against a metal support, which as mentioned above causes much worse heat. The Tormek tends to contact only a small area of the convex surface, due to a convex surface meeting another convex surface. It is hard, working by hand as I do, to hold on that very small contact point. I end up with lots of small "facets" on the bevel, which I then end up having to grind off on a stone. Maybe I need to just continue on the Tormek until I grind the small facets down to some sort of continuous concave bevel perpendicular to the sides of the tool?

The accessories I have for the Tormek (older green model) which I thought might help me maintain a grind perpendicular to the tools sides did not work for me. I was ending up off perpendicular despite the tool holder. I am a little reluctant to spend money on the "newer" version Ruperto mentions above as I have not found any of the guides I have for my Tormek useful. I am curious what posters using Tormeks and or grinders are using to hold their tools? I thought many were free handing their tools on their grinder? At least when I work by hand I can adjust as I go, using tool rests in the past I seemed to end up with an out of place concave bevel that was very hard to correct, requiring even more grinding than the bevel originally needed.

I saw one positive reference to the Sigma Select II 240 stone. Although it may not work as well as grinding maybe it will be faster than the 3F carbon 700 and easier to use than a lapping plate?

[Derek Cohen]

Hi Mike

I have had success using the Tormek knife jig ..



Regards from Perth

Derek

[Mike Holbrook]

Derek, thanks for the idea, did not think of that. I sharpen my kitchen knives on a Spyderco, triangle sharpener. For some reason I have the knife jig though which I have not used. I will try it out tomorrow, AM.

[Mike Holbrook]

Good call Derek,
I was able to get the most even bevel yet using the knife jig on a, 10" blade, straight drawknife. The handle just barely clears the buffing wheel and I have to raise the tool rest about as high as it will go. The bevel the Tormek is making is not quite reaching the edge of the tool, but I think as it works further into the steel I will be able to get the bevel where it needs to be using the tool rest and knife jig. The knife jig allows one to apply tension against it, maintaining a specific position when sharpening. The rounded knife jig surface that rests on the round tool bar still allows one to maneuver the blade around on the stone in a predictable fashion. Next I will see if I can work a drawknife with a curved blade with this jig.

Great posts, nice to be talking techniques to help specific tools work better.

[Andrew Pitonyak]

I have a Tormeck and a belt sander, which seem to produce flat facets across bevels that I wind up having to remove by hand...My attempts to hollow grind on my Tormeck thus far have been dismal failures. Suggestions?

Using the Tormek, I need to be careful when I tighten the chisel (or what ever) into the holder. I need to tighten both sides of the holder carefully so that I don't cause some chisels to skew, especially if the top is not perfectly parallel to the bottom.... So, as I tighten things, I do a bit on the left, a bit on the right, a bit on the left, a bit on the right ... I also check to make sure that things are square between the blade and the holder.

Is the side edge of the thing that you are sharpening perpendicular to the cutting edge? If it is not, then if the side edge sits against the edge of the clamp holding the chisel then you will not grind square to the blade.

Note that the two problems mentioned above are also possible when using a sharpening guide when you work by hand, but, I have found the Tormek guide to be more persnickty with respect to tightening, probably because it has a left and right side to tighten and my hand guides all have only one (I think.... been a while since I used them).

Finally, I assume that you are using even pressure and not making the mistake of moving the blade left and right to the edge of the stone and back, because if the blade is wide, then the center of the blade will spend all the time on the stone and the outer edges will not so you will wear away the center faster than the outer edges, but, that is not the problem that you are mentioning.

I have never figured out how to use the Tormek to flatten the back effectively.