I inherited a small low angle block plane from my dad.
Nice looking with brass buttons, but upon inspection the blade wasn't straight. I removed it and checked, it was square and just needed sharpening, but when I looked at the cast iron base, the seat of the blade at throat level was thicker on one side, making it impossible to align.
The sides were also both slightly more that 90° which didn't help.
The easiest solution was to remove the adjustable front throat and reform the blade seat with a file.
It worked, and after flattening the foot of the plane and sides using sandpaper on a granit slab, then sharpening the blade I now have a very nice block plane.
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