As I'm tuning up a couple of planes, I noticed something.One of the first mentioned tune-ups is flattening the frog face . I use a file, but I've done a fair bit of filing in my work. OK,fine. But what about the blade. Nobody seems to mention the flatness of the blade. I'm using the word blade, but cutter or iron, depending apon country or manufacturer usage. That is the other half of the mating. On the old blades I'm working on, the word flat can't be used in the same room as them. One is a laminated Stanley and the other a Anchor brand, so both were worth the effort.After some careful hammering, I resorted to using to using a dial indicator mag base and a 6x48 sander. Tricky but doable. Thanks Derick Cohen (sp). It's just something else to think about.