I bought a used #4 Stanley in a local store. It was in bad shape but I managed to clean it up except for the Lever Cap. I decided I would use it as a scrub plane. I increased the camber on the blade and used a file to open up the mouth. It works fine for the intended purpose.
I then bought another plane from another local pawn shop. This was an Award plane made in India. Identical to a #4 Stanley except for the Cap which had a screw instead of a lever. This plane was out of the box like new.
I decided I would use this as a high angle smoothing plane. So I sharpen the blade and put on a 20 degree back bevel.
I could not do anything with this plane. I closest I could get the cap iron was about 3 mm from the edge of the blade. The blade was as it protruded from the mouth was skewed. I messed with it for a few hours no luck.
So then interchanged the cap iron with the cap iron on my old #4 Stanley. And it worked. Not only that but the cap iron from the Award plane worked on my Stanley plane. However the blade was still skewed.
So I switched the cap iron – blade assembly in the old #4 Stanley with the Award plane and every thing worked.
I now have a like new out of the box mongrel scrub plane and a beat up old old high angle smoothing