I got a crappy buck bros no 5 jack plane and shavings get caught between the iron and cap iron. I checked and sure enough there is a huge gap between the back of the iron and cap iron. I lapped and polished the back of the iron and did the same for the cap iron. Now the back of the cap iron is nice and flat, but it is askew, almost like there is a twist or warp in my cap iron.
When you mate the surfaces together it touches at one corner (red circle in picture) and then gets larger as you move to the other corner.



Photo Feb 26, 2 35 25 PM.jpg

I set the cap face down and sure enough one of the sides is about 1mm higher (further away from the floor) than the other (red circle in picture).

Photo Feb 26, 2 44 35 PM.jpg
I'm not sure how I go about fixing this though. I thought I could just work the high side on a 300 diamond stone but that hasn't worked.


Should I be filing the edge down, i.e., holding it perpendicular to a file, or just continue working the underside of the cap iron on the diamond stone? Maybe doing it an angle?
Any help on how to reset the geometry would be appreciated.