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29.138
Figure 3-9.—Six-inch jointer.
table an amount equal to the desired depth of cut.
The usual depth of cut is about 1/16 to 1/8 inch.
The level of the outfeed table must be
frequently checked to ensure the surface is exactly
even with the highest point reached by the knife
edges. If the outfeed table is too high, the cut will
become progressively more shallow as the piece is
fed through. If the outfeed table is too low, the
piece will drop downward as its end leaves the
infeed table, and the cut for the last inch or so will
be too deep.
To set the outfeed table to the correct height,
first feed a piece of waste stock past the
cutterhead until a few inches of it lie on the
outfeed table. Then, stop the machine and look
under the outfeed end of the piece. If the outfeed
table is too low, there will be a space between the
surface of the table and the lower face of the piece.
Raise the outfeed table until this space is
eliminated. If no space appears, lower the outfeed
table until a space does appear. Now, run the
stock back through the machine. If there is still a
space, raise the table just enough to eliminate it.
Note that the cutterhead cuts toward the
infeed table; therefore, to cut with the grain, you
must place the piece with the grain running
toward the infeed table. A piece is edged by
feeding it through on edge with one of the faces
held against the fence. A piece is surfaced by
feeding it through flat with one of the edges
against the fence. However, this operation should,
if possible, be limited to straightening the face of
the stock. The fence can be set at 90° to produce
squared faces and edges, or at any desired angle to
produce beveled edges or ends.
Only sharp and evenly balanced knives
should be used in a jointer cutting head. The
knives must not be set to take too heavy a cut
because a kickback is almost certain to result,
especially if there is a knot or change of grain in
the stock. The knives must be securely refastened
after the machine has been standing in a cold
building over the weekend.
Each hand-fed jointer should be equipped
with a cylindrical cutting head, the throat of
which should not exceed 7/1 6 inch in depth or 5/8
inch in width. It is strongly recommended that no
cylinder be used in which the throat exceeds 3/8
inch in depth or 1/2 inch in width.
Each hand-fed jointer should have an automatic
guard that covers all the sections of the head on
the working side of the fence or gauge. The guard
should automatically adjust horizontally for edge
jointing and vertically for surface work, and it
should remain in contact with the material at all
times.
When operating the jointer, observe the
following safety precautions:
·
Always plane with the grain. A piece of
wood planed against the grain on a jointer
may be kicked back.
·
Never place your hands directly over the
inner cutterhead. Should the piece of wood
kick
Figure 3-10.—Operating principle of a
jointer.
3-9
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