On Sun, 20 Mar 2011 00:51:24 +0000, Phil Addison
wrote:

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
http://www.mtmc.co.uk/Product.aspx?P...earch&PPGR =0,
are held by a flat slotted plate (51) that is held by 2 Allen screws.
After adjusting, these 2 screws are covered by a further curved
retaining plate (52) that is held by 3 more Allen screws, so there will
be 5 altogether clamping on the first flat plate. The bladed have
grooves in them that locate them in a fixed radial position against the
flat plate. They can be slid out sideways from the plate once the curved
cover is removed.

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 http://www.axminster.co.uk/downloads/700360_manual.pdf

Am I missing something here, or does anyone have any tips for making the
task more predictable.

Thanks for the various advice. In the end I tightened the blade holder
just enough to hold the tungsten carbide blade in position, then used
the thin 2" wide blade of my 90 degree square to push the TC blade and
the flat holder flush with the sole plate, and then tightened it up. At
this stage the TC blade will still slide out sideways from the flat
carrier. Screwing on the curved clamp plate with the 3 Allen screws
bends the blade holder slightly to clamp the TC blade against the rotor.
Taking the drive-belt cover off makes it easier to turn the rotor.

Testing again with the 2" flat blade verified that the cutter remained
both parallel to the sole plate and at zero cut. With slight finger
pressure on the blade of a 90 degree square you can feel the cutter just
scraping it as you turn the rotor.

This was easy to do and overcame the hit and miss (well mainly miss) of
the first method I described. And the planer now makes beautiful cuts
after its makeover.

Phil