Making a double convex palm plane

I'm so cheap. I knew I'd need a special tool to carve the insides (concave sides) of the tops and backs, and that tool was a double-convex palm plane. Lee Valley / Veritas makes a nice one, but it's $80 delivered, and besides, I like making things. So...

My son gave me a nice cast-iron palm plane this last Christmas, and I decided to use it as the base for the plane. All of the parts were a little rough. I started by truing the sole flat, and regrinding the cap flat and thinner at the base. I had a nice scrap of bubinga for the falsie sole.

I glued the newly-flattened plane sole to the bubinga with JB Weld, which glues anything to anything, although not beautifully. 

On my stationary belt sander, I first ground a longitudinal radius of maybe 5 or 6 inches, then a radius of maybe 2 inches or so. This was all by eye and feel. When it felt fair in my hand, I sanded it up to about 250 and polished it with a 220 sanding sponge. Then I spent about 3 hours chiseling and filing out the slot for the blade. 

I ground and honed the blade to a slightly wider radius than the sole. If you don't do that, the edges don't extend as far below the sole as the center when you set it up.  I did the rough grinding on my stationary disc sander, and I have a set of ceramic Shapton stones I like for sharpening. The blade was not very flat to start with, but I'm lucky it was a little concave, as you can see, rather than convex, which would have taken forever to flatten. 

Here's the assembled, working plane. Not very pretty, but it works really well. On first tests, I found I had to make the front part of the throat more vertical for chip clearance, and I filed the cap really thin and sharp near he blade. It makes consistent long curls in scraps of both cedar and mahogany, but I haven't dug really deep with it yet.  I may or may not decide to clean up the exterior appearance. If it works as well as I hope it will, maybe it'll be nice to it.