I just got a Stanley 40½ scrub plane with a broken lever cap (as advertised). No big deal, I figured I’d just make a new cap. But the break didn’t look so bad, it was clean break and fit well so I decided to try and fix it. I used brass, hoping that the flux would clean the cast iron and give me a good join. But the break was in the area of the highest stress (at the fulcrum) so it needed re-enforcement; I added “guy wires” to the back, in the form of steel welding rod on each side. Gotta say I hate brazing cast iron, it is soooo dirty, I have a really hard time getting brass/silver/silicon bronze to stick and getting a clean weld. This one turned out OK The photo of the top shows most of the crack has been filled with brass. As a test, I cranked down on the thumb screw really hard with no issues so I’m calling it good. (The guy wires are in tension and press the break closed when the screw is tightened, so break is in compression, which is good). The casting is nice but really crudely finished so I cleaned it up. And the cap screw is another bastard Stanley thread: ¼x18 (vs NC ¼x20).
I noticed that the cap tended to creep up so I filed a very shallow groove for the cross rod with a chainsaw file (they rock). Fixed. I looked at some other #4o lever caps and noticed they have another set of side ribs to trap the rod, Stanley must have noticed the same problem.
I waved the iron over some diamond fairy dust and the plane works quite well. And gets really hot. I fried the hand that holds the knob so I measured the sole temp – 135ºF!