A use for discarded (rusty) rulers

Attachment 46191Attachment 46192
This is the sole of a Stanley Bailey 4 1/2 and it is convex and probably has been since it was bought new.
How convex, I did not measure, but it was useless. Not wishing to waste the 50p it cost me, I decided to rectify the defect.
Remembering I had two rules, which had been in the stockpile for years (they were salvaged) and, being rusty, even if cleaned, the markings would no longer be visible, I thought to use them, just to scrape at the marking fluid, before using the engineer’s scraper.
Now the plane is useable, but before posting the picture of it, let me tell you that it is not an example of precision scraping, which I can’t do. In fact parts of the plane are now concave, which is approved by those in the know, perhaps to reduce friction? I don’t know.Attachment 46193

What you need is two more reject planes. Then you can practice the tried and true method developed by your countryman...

https://ericweinhoffer.com/blog/2017...-plates-method

Handled properly, concavity of plane soles won't be an issue on material longer/ wider than the plane. The edges being true with each other assures the relative flatness. With the throat matching perimeter, setting blade depth remains same as the very best made plane would be. It's a toss-up about friction reduction, lesser contact is certain, but might be air cushion instead of reduced surface.
Some heavy fixtures introduce compressed (filtered) air for movement across surface plates, no recess, just vent holes connected by slots, need be.

The first plane I bought, secondhand, was concave. It took me a long time to realize. By then, I had bought a new no 4 Stanley. This was badly warped. I had both surface ground and I estimate the latter was at least 1/8” out of square. This didn’t cost very much. But, pardon me, if you have ever struggled to use a plane, it may well be because the mouth is either higher or lower than the ends. Since the post above, I have flatted two more planes, one convex and the other with high spots here and there.. I remembered an off cut of granite worktop and stuck 80 grit abrasive, and that I found was rather quicker, although it might have resulted in uneven ends.. But if the plane is concave, you would have the blade projecting too far, it will chatter and the shavings will jam the mouth, it won’t be a comfortable ride and the surface of the wood may look as if it’s been adzed!