Powermatic PM15 - Manual (Page 10)

10
6. Tighten the gib set screws, beginning with
the center one first. This will lessen the
tendency of the knife to creep upward.
Sharpening Knives
Your Planer/Molder is a high precision machine,
and the knives are an integral part of that
precision. For the Planer-Molder to work most
effectively, the knives must be ground on a
machine that will produce a high quality
professional edge.
Knives should be sharpened promptly when the
edge is lost rather than letting them get to the
chipping and tearing out stage. A regular
schedule of sharpening should be arranged.
Always sharpen knives at the recommended
levels and angles. Figure 8 shows the proper
bevel for the planer knives.
Proper grinding done at the right time will do
more than anything to prolong the life of knives.
More dulling occurs in the last 20% of the useful
life of the knife than in the other 80% of use. If
the knives are sharpened on schedule and
before the last 20% of possible use they can be
resharpened with .002” to .005” of material
being removed. If, however, they are sharpened
during the last 20% of the useful life, it will be
necessary to take off .006” to .010” of material.
TIP: An occasional use of a hand held hone will
extend the sharpening life of the knife.
If your planer knives have struck bits of dirt,
gravel, or other foreign objects, etc., they will
leave behind nicks and burrs on the cutting
edge of the planer knives. If the nicks are heavy
enough to the degree where the nick shows up
in the same spot on all three knives, this will
affect the appearance of the finished surface on
your stock.
Occasionally you can hone some of the nicks
out with a knife hone immediately after the nicks
occur. These nicks must eventually be ground
out in the sharpening process if your planer
knives are to do an effective job of planing.
This type of knife damage usually nicks the
knives in the same cutting circle. A simple way
to remedy this is to stagger the knives on the
cutterhead: move one knife 3/32” to the left, the
next knife 3/32” to the right, leaving the third
knife in its original position.
If only one knife is nicked, the other knives will
clean up the rough edge left by the nick, and no
adjustments may be necessary.
Figure 8