I acquired an oldish Bosch PHO 100 planer and having cleaned it up I'm trying to adjust the blades. It seems very hit and miss on this machine.
The blades (755), see exploded diagram
I suspect that I should not have loosened the flat plate at all, it possibly being a factory setting, but this machine was old and had muck sticking the blades so it wasn't apparent that they should slide out!!
The flat plate is slotted to allow the blade height and angle to be adjusted but there is no micrometer adjustment of any kind, you just have to loosen the screws a bit, try to move the blade slightly and re-tighten, then check the blade height and paralell-ness.
I'm attempting this by clamping the planer upside down with the cut depth set to zero, and laying a strip of wood over the blade. Rotating the blade cylinder assembly (850) will then moves the wood an amount proportional to the blade protrusion. The idea is to get near zero movement of the strip at each end of the blade (and for both blades), showing the blade is both parallel to the sole plate and hardly protruding at all.
The trouble with this planer is that the slightest loosening of the screws lets the blade move, hence it is a frustrating business to get it right. By the way, I am not fitting the curved plate (52) until I have completed the alignment checks satisfactorily.
Axminster sell an alignment gauge, but it won't help with stability of the adjustment
Phil