Hollow Grinding Fixture ( More Than a Jig)

At the Harrisonburg show, Pop's ( James Poplin) had a new device that was on a Bader BIII grinder. It was a hollow grinding fixture. The simplest way to say it is, "This compares to most hollow grinding jigs the same way a MAPP arm compares to a work rest". The wide work plate keeps the blade in a straight plane as you grind. I think this has potential.

The device mounts on the work arm, and the work plate flips up over the contact wheel. The blade is held against an upper stop that you adjust to set the hight of the hollow grind. The depth of the hollow is adjusted by setting the height of the work plate in reference to the wheel. Give him a call for more details.

I attached some photos of it from different angles.

He says that a flat grinding work plate version is in the design stages.

 

I didn't grind a blade on it, but simulated a grind with the blade shown. The stop is set at the top of the cutout to run the edge along. The platform height is set by the threaded arm. This will raise the platform for a smaller grind, or lower it for a wider and deeper one. Once set up, you just hold the blade by the tang and with a finger or two against the outer side. Sweep the blade along the stop and the grind cuts evenly. As you reach the tip, just rotate the tang down to keep the edge going along the stop. I didn't ask, but I believe it can be used for any contact wheel from 6-14" ( which will also change the grind height and depth).

The overall use isn't much different than doing it freehand, but the wide platform keeps the blade straight, and the stop keeps the grind from wandering. I guess the biggest advantage is repeatability of the grind. If you were hollow grinding twenty blades, every one should have an identical hollow grind.

 

This is a year and a half old thread. Pop's Knife Supply was the person carrying these.