Hunting Knives

[webmxx]

Virtually all of my hunting knives are not a flat piece of steel with a sharp edge. Either they are triangular from back to edge or have all sorts of concave/convex curves between the same. This makes it impossible to set any angle with the anglemaster. So I have been using the mark-a-lot to color the bevel, etc. However, it seems that if I get it set for one side, when turning it over to do the other side the bevel is not the same. It seems it's very difficult to get these sorts of blades "square" in the knife jig. Any techniques to get the knife square in the jig? And although you can set the bevel with the marker, I can't see how you can get the bevel to an exact set angle, particularly if you know what angle that a knife is supposed to have. Any help there?

[jeffs55]

It is impossible to follow any large curve on a knife. I am sure you have observed that if you follow the angle on the straightest part of the blade that you are going to grind more when reaching a curved area. This also applies to the tips of your knives. They are going to be ground more with a resulting wider grind pattern. I have never tried it but increasing the angle on the curve would lessen the bevel produced. This would be very tedious though. I dont understand your settings not being the same from side to side. If you are incredibly dexterous you could use the jig on the straighter edges and freehand the curves. Once again, that would be very tedious if not impossible. You might as well forget a convex curve on the stone. Better to use a Lansky type device that has a much narrower grindng surface. I am am anxious to see if there is any better advice. Good luck.

[webmxx]

The side to side issue: the jaws of the jig are flat, square pieces of metal. A kitchen knife, for example is a flat piece of metal with an edge. So, when the jig grips the blade, everything is "square". The hunting knife, on the other hand, isn't flat on its sides...it has the convex/concave contours....so the jaws of the jig are trying to grip a curve, its difficult to get the blade 'gripped' with the edge exactly lined up with the center of the jig jaws. That results on different bevels on each side of the edge as the knife is flipped from side to side.

[Jeff Farris]

It isn't the shape of the blade that is causing the uneven bevels, it is the thickness. If you look at the jig from the side, you can see that the base of the jig is formed so that its plane is a little below the centerline of the jig axis (the shaft that rides on the Universal Support).  Theoretically, the jig is perfect for a blade that is exactly twice the difference between the base plane and the centerline. Practically speaking, it works very well on blades between 1/16th and 1/8th inch in thickness at the back of the blade, but will give less satisfactory results the further you go either direction of those measurements.

One answer for blades outside the "sweet spot" is to index the blade back into the two pins in the jig. Sharpen one side, then take the blade out and turn it over, again indexing against the pins. Now, you're using the same reference for each side of the blade.  This will give you two identical bevels, but involves an extra step.

I've asked the brains of the operation to either join this discussion or send me an e-mail with any additional thoughts.

An unusually shaped blade can make setting the bevel with the AngleMaster challenging. Deep hollow grinds made with small diameter stones are an example. In general, divide the desired included angle by two and measure to the plane of the blade immediately behind the bevel, rather than trying to measure the bevel itself.  For example, for a standard 40 degree included angle, set the AngleMaster to 20 degrees and align the flat edge of the angle indicator to the body of the blade just behind the bevel, with both points of the AngleMaster and the edge of the knife all touching the grindstone.  On hollow ground blades you have to approximate the fit of the angle indicator to where the plane would be had the taper been flat ground instead of hollowed. I've found that increasing the angle by 2 degrees and fitting the angle indicator flat onto the hollowed taper works very well on most hollow ground blades.  That is, I set the AngleMaster for 22 degrees and fit the angle indicator flat onto the body of the blade just behind the bevel.