A Couple of Blade Grinding Jigs

A Couple of Blade Grinding Jigs

Derek Cohen (in Perth, Australia)

>1. Flattening the back of a blade.

I always find flattening the back of a back a real pain in the whatsit. This includes both chisel and plane blades � blades that are either rounded or pitted. My strategy to date has been sand paper on glass.

I had in mind a blade that I wanted to use in my Spiers infill smoother. It had potential but was pitted on the back near the edge of the blade.

What I have now done is to basically create a surface grinder out of the disk sander section of my belt sander combo.

Sanding disks are all easily and quickly swapped over since they are Velcro backed. The sequence begins with 120 grit, moving to 240, 320, 600 (25 microns) and 1200 (9 microns). This is then polished on a leather strop disk with Veritas green rouge (.5 microns).

The idea for using the disk sander only gelled when it occurred to me that I could use the magnetic base of my Dial Gauge to hold blades securely against a fast spinning disk. Note that the right side of the sander is used so that the disks do not turn into the blade (since the 600 and 1200 could tear).

This worked extremely well. I have successfully flattened several plane and chisel backs. Contrary to what I expected, the blades do not heat up much. In any event, I dunk them frequently in water.

I was able to purchase disks up to 320 grit. The 600 and 1200 I made by gluing wet-and-dry paper on an old sanding disk.

The leather strop is a piece of chamois leather stretched and contact glued to another sanding disk.

Here is a result on a blade that was, as I stated earlier, quite pitted. Taken after 320 grit.

And finally the Spier planning a piece of Grey Gum (this has got to be the one of the most difficult woods to plane � unbelievable constant reversing and interlinked grain in a very hard wood).

2. Building a dovetail chisel

In a recent post Mike on WoodNet showed off his Blue Spruce dovetail chisel. Damn, I want a set!!

Len noted that the side angles were hollow ground. This was one of the features that I found so attractive and had been giving it a little thought as I had been developing a design on rolling my own.

What I have here is the jig I built to hollow grind the sides.

Basically the idea is to use my high speed grinder. This is a 6" machine set up with the Veritas grinder rest and a 60 grit white Norton wheel. While I freehand hollow grind blades, such as those for my Gordon planes, I also have the Veritas blade holder, and I thought that I could press this into service as part of the jig.

I planned to set the side angle at 30 degrees on the practice chisel. To do this I used a Tormek angle setter (no, I do not own the Tormek - just the protractor). It is very useful.

The jig itself is very simple - just a piece of hardwood into which are set a few rare earth magnets. A section of thin steel acts as a fence for the edge of the blade. It is loose to allow for adjustment, and held firm by the clamp of the Veritas blade holder.

Note that the jig is inserted upside down here for visibility.

It is used like so ...

Here is a before ..

.. and after ..

So the practice chisel seems to work quite well. But I couldn't proceed beyond this point. To my great frustration I only then discovered that the grinder's body projected beyond the 6" wheel and prevented the chisel body being ground in the opposite direction. I shall have to wait until I get a 8" wheel for the machine. So there we wait ..

Regards from Perth

Derek