Monday, June 30, 2008

Sharpening a Dovetail Plane

Abe Lincoln once said "Give me six hours to chop down a tree and I will spend the first four sharpening the axe."

Well, I spent 6. 5 hours on Saturday fiddling around with the blades on the dovetail plane and got pretty good, but not perfect, results. The blades were easy—too easy—to sharpen. Too easy, because I realized they had not been heat treated. That's fine if you're working with pine, but to plane curly cherry meant having to resharpen blades that were being nicked by the hard wood and which dulled quickly.

Rather than take the time to heat treat the irons in order to produce a clean dovetail—I'm terrified of propane torches and need to spend several days working up my nerve to use them—I forged ahead with planing them, and resolved to make scratch stock to clean up the tearout.

To sharpen the plane blades, the backs first needed to be flattened. I used drywall screen sitting atop a sheet of glass, but you can also use a sheet of coarse sandpaper clamped to a known flat surface, like a cast iron table saw or jointer bed. From there, I polished the back on 1,000 grit and then 8,000 grit waterstones. A veritas gauge helped maintain the bevel angle while sharpening it on the 1,000 grit stone, followed by the 8,000 grit stone.

Sharpening the side bevel was a little trickier. It was rounded over, so I first flattened it with a file and then used 1,000 and 8,000 grit slipstones to polish the bevel.

Scratch stock is very easy to make. The trick is to make sure you polish both sides of the metal as well as the edges. You want very square edges. I rough-shaped the profile with a hacksaw, used a grinder to finalize the shape, flattened the edges with a file, and used an 8,000 grit waterstone to polish all edges. It only took about a half hour to make, whereas, had I elected to heat treat the blades.....well, let's just say, this being two days later, I'd still be trying to bolster my courage.