I finally took my great grandfathers #4 Dunlap bench plane out back and cleaned it up this afternoon. The original forum post is here
First I made sure that I had everything ready and all the protective stuff I would need to safely work with phosphoric acid. I soaked the small parts in a tupper ware and scrubbed stuff in my oil change catch pan. Gotta love a multi-tasker! And of course some tunes on the iPhone.
The Krud Kutter Rust Buster really worked quickly, the rust was pretty easy to scrub off.
The rust remover leaves a rough etching on the steel’s surface. I was surprised to see just how rough it left all the parts of the tool. Some of the parts that were not rusty were still a bit discolored.
I was able to remove most of it with some car care products I had laying around. I wished I had some Mother’s brand metal polish, but this stuff worked in a pinch. The Blue Magic is similar to the metal polish from the same brand but thinner and has no silicon. You can see the before and after on the blade leaning against the blue magic bottle.
I used a spray adhesive to attach some black sand paper to a piece of 1/8 steel plate. It was conveniently shaped to hook over the end of the bench. I learned pretty quick to attach it flush to one edge so that you can work what you need to.
After a few minutes I realized just how wonky the sole really was. I was in for a long afternoon.
A while later:
And done! Its pretty darned flat but not mirror polished. I figure another hour would make it mirror flat, but its nice and smooth. I cant detect any pits or ridges with my thumb nail, it feels incredibly smooth.
I also filed down the casting marks on the mating parts of the top of the sole. I lapped the mating part of the frog, chip breaker, and blade as well. everything seems to mate up pretty darn flat. I guess old great-granddad never really set his plane up!
The mouth of the plane had machine marks which also needed to be filed.
I still have to redo the knob and tote, but that will have to wait until tomorrow. I am really happy with the results, I slapped it back together and got whisper thin shavings immediately.
Edit: I changed the title and some of the blog to reflect the definite identification of this as a in fact a #4 style plane.