Than we Differ neil.I have always gone by the experiance of others that I respect.
I worked with a very old man a few yrs back building a natural rock wall,I worked for free just to learn,no morter,no supports,all free standing.
He was Crass,he was not very bright,he had no formal education,but he had 60 yrs experiance in the art of Rock walls.
the above has nothing to do with metals,razors etc,but when an old Machinist with decades under his belt tells me something,(call me stupid) I believe it.