|Top view of asymmetrical bevels.|
|Lucy Peña measuring a finished bowl.|
On my second trip I wanted to bring a bunch of carving axes for the artisans to try. Most of them carve the outside of their bowls with fairly light adzes or machetes and I thought a heavier tool might increase efficiency. I rounded up six decent hatchets and went to work tuning and sharpening them. This is the method I developed for reshaping the bevels.
With that brief overview out of the way, back to the project axe.
|Removing the handle.|
My axe was fairly straight at the edge and I wanted it to have a little bit more curvature. I drew a curve that looked good to my eye. Next, I created that curve by setting the grinding platform perpendicular to the wheel and grinding material directly from the edge. This operation creates a flat at the edge of the tool, which can be a useful reference point in the following steps. When I measured the curve later, it was close to an arc of a circle with an 11" radius.
The heart of my grinding technique is the pivot stick. I made mine so that the point that sits in the vee-arm was 11" from the edge of the axe when the axe head was clamped in place. This distance approximates the radius of the curve that I drew onto the head and then ground to shape in the previous step. If the curve of your axe has an 8" radius then the distance from the edge of your axe to the point should be close to eight inches. There is some room for fudging here, so don't get too crazy figuring out the exact curvature and radius.
|Pivot stick top view.|
|Pivot stick side view.|
|Complete set up.|
|Setting the angle for grinding.|
|Checking the set up.|
As I move the axe back and forth I slightly raise the corner of the axe that is not in contact with the wheel. I do this to clear the grinder motor, but it also seems to keep the bevel aligned properly. Remove the assembly from the tool rest and check your progress regularly. If the axe is not properly aligned the bevel will not be a consistent width. Light tapping of the head to adjust its alignment with the pivot stick can usually remedy this problem.
|Wide bevel ground.|
|Estimating the narrow bevel.|
|Short bevel complete.|
As I grind both bevels I frequently check the flat left from grinding the edge to a curve. I try to keep the flat straight and even in width. In the picture above, note the inconsistencies in the width of the flat. When I return to the grinder I remove more material from the areas where the flat is thicker and avoid grinding in the areas that are thinner. As you can see, the corner of the blade in the left of the picture above has no flat at the edge, which means the bevels are meeting there. When I returned to the grinder after taking this picture I made sure not to grind that corner any more. A word of caution, the thinner that flat gets, the more likely you are to overheat the edge on the grinder. I use a light touch and I keep a bucket of water near to cool the axe head as needed.
|Sharpening the axe.|
Even without the handle in the head I couldn't resist sharpening the edge. I used diamond paddles to hone the hollow grind, and then finished it off with some careful stropping. It was slicing through pine endgrain beautifully in under five minutes. The hollow grind is quick to sharpen and makes maintaining flat bevels a simple matter.
In the next post I'll cover fitting the handle to the eye and making adjustments to the included angle of the edge.