I have been using this jig for a few years now and it sure takes the frustration out of hollow grinding. First you have to make an adjustable( height) bracket for your grinder that has a radius to move the blade across. This sets the proper centre line height for the grind. Cut out a piece of wood in the shape shown about 1 1/4 inches thick drill two holes in it, these will be used to install 1/4 in dowels to support the knife. On the wooden jig mount a rare earth magnet ,one on each side, this is what holds the knife blank to the wooded jig. These magnet can be purchased with a holder that is screwed to the wooden jig.After repeated use and grinding different knives you will most likely have to replace the wooden jig because of all the dowel holes you have drilled. I did not have a hollow ground blank at the present time, so the knife shown on the wooded jig is for demonstation only to show how the blade fits on the wooden jig. Happy grinding
Dan, this one is a 3.5 inch diameter and made from steel but you can made it from a piece of wood or Nylon and a 3.5 to 4 inch diameter should work just fine. The big thing that has to be adjustable is the rest height in relation to the centerline of the hollow grind wheel. My grinder was never made for an adjustable rest so I kind of put something together to make it work. If you have a grinder with an adjustable (up and down) rest height, then it is real simple. Just take 3.5 inch diameter piece and cut it similar to the shape of mine, put a couple of rare earth magnets into the bottom of the peace and stick it on the rest. You are in business and ready to grind.
What type of grinder is that? I have something similar and have not been able to find out where it came from
It is my own design. All of my equipment forge,lap wheel,rolling mill, press, 12 inch lap wheel and buffer are my own design. Now you know why my Avatar looks the way it does !