Hand Tools Archive
Bill Tindall, E.Tn.
As I reflected on the preparation of chisels for the project at hand I tried to justify what I was doing in light of all the work that has gone on in the past few months.
David has provided a tutorial on preparing a chisel with a Unicorn Profile and described in detail the rational for why it is the way it is. I find no fault with the recommendations nor the justification for them. So why am I staying with Unicorn-Lite, defined as doing what you have always done and follow with a brief buff to add strength to the edge?
To review: David recommends 20 degree primary bevel, 23 degree secondary bevel, buff. I am hollow grinding 25 degrees, refining the 25 degree bevel with finer abrasives, front and back, then buffing.
Some differences between our work.
One difference is experience. I have spent at least 1000 times less time honeing things than David. I need a process that works reliable and consistently when one's sharpening needs occur days and weeks apart. I have not had need to sharpen a chisel in nearly two months when I last was making drawers for the desk.
A hollow ground bevel sucks down on a lubricated diamond plate which provides reliable registration of tool bevel to "stone". What ever angle I grind at will be reliably replicated, and maintained, in the subsequent honeing steps. In the end I reliably wind up with a hollow bevel at 25 degrees vs David's 23 degrees.
Diamond cuts any steel quickly, which is the reason I have advocate using it for quite some time. To refine a hollow ground bevel with a "fine" fixed diamond plate or 15 micron diamond on cast iron takes less than a minute. Following with 1 micron diamond on cast iron takes less than a minute. For me the time advantage of what David is doing is not significant to me.
Inertia- Adding buffing to what one already does is a small step forward. I can maintain focus on how I am going to engineer the drawer support for this rock topped table. Adding 2 seconds on the buffer doesn't take any brain power and I can get on with the woodworking.