Thanks Bruce,
I just tore my rather ancient Victa apart for another look, and it has a different design from the one in your sketch. There is a boss pressed or shrunk onto the crankshaft, but no boss on the blade plate which is a fairly elaborate pressing but flat in the center. The X-recess washer goes on after the blade plate, then a special, heavy washer goes after the X-recess washer. The special washer has a boss on one side and a recess on the other. On the boss side it has "BOLTHEAD SIDE" in raised-up lettering. By torquing up the bolt, the X-recess washer gets squeezed between the recess side of the special washer and the blade plate. I guess this makes sure the X-recess washer gets squeezed completely flat, by allowing the end of the crankshaft to enter the washer recess if necessary. By the way, if someone has invented a better way to hold the crankshaft from rotating (I just use a long piece of 2mm steel plate about 40mm wide) I'd be interested in seeing a picture or sketch.
