Joint Knife
© Frank Ford, 4/25/98; Photos by FF
Here's a tool I've been using forever. Actually, this is the third one. One, I broke, the other I lost.
I go to the paint department and look for the best quality flexible putty knife I can find.
Then I spend a couple of hours grinding it just right, by rubbing it on sheet after sheet of silicon carbide paper clipped to my marble slab:
I feel it works best if I can press the blade down on a surface and see the blade curve gently all the way to the very tip. It usually takes quite a lot of thinning of the last 1-1/2 inches of the blade, but after a while I can get the blade to lie perfectly flat as I press it down to the surface. As I press down, the blade curves smoothly all the way to the end.
I stress the preparation of this tool because I use it so often. It's the first one I reach for to separate any glue joint:
Here, it slides right under the fingerboard, and because the tip is rounded and sharpened from both sides equally, it tends to follow the glue joint.
Nothing like my joint knife for slipping under pickguards:
I can even attack the joint from this elevated angle because the knife is flexible and lies flat against the top as I press down.
This knife is curiously sharp. I say curiously because that wasn't my original intent. In the process of thinning and beveling I also polish the surfaces of the blade to a high shine so it will slide easily and not scratch a finished surface. The last step in polishing is a trip to my buffer with some rouge on the wheel.
This final buff has the effect of polishing and sharpening the leading edge. In fact the knife is always sharp enough to shave with. Because the sharp edge is rounded from both surfaces by the buffer, it will slide right along a finished surface without a chance of digging in.
It's also the knife that everyone in the shop reaches for at lunchtime. It makes the dang bestest pizza cutter you ever saw!
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