Fettling an old Block Plane (page 2)

Repeat the process for the sides. The important thing is to remove any lumps...
... and to have the sides
square to the sole using an engineer's square. This will enable you to
"shoot" edges and ends square using a shooting board.
Take the sharp corners off the nose of the sole to avoid nasty damage when planing over corner joints etc.

Vacuum clean the iron dust as it rapidly turns to rust powder.

There's a good chance with a second hand plane that the blade has been poorly sharpened or even ground too hot. Look for any blue marks. You will have to cool-grind the blade back until the blue metal has been removed as it will most likely be soft. If you can use a water cooled grinder like this Tormek. Grind to 25 degrees.

Hone the back of the blade on a stone or diamond plate like this one. You will have to take some time to flatten the blade to a point where the blade has been honed all the way across for a length of about half an inch.