Chapter 21 Processes Used to Separate Wood Materials
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time-consuming, and the knives must be handled
with extreme care. Another drawback of the knife-
blade planer is the danger of kickback. This means
that it is possible for the cutter to bite into the stock
so that the workpiece is thrown out of the machine
back toward the operator. Kickback is usually caused
by such operator errors as feeding stock that is badly
warped or bowed, taking too large a cut in one pass,
or feeding stock that is too short to be safely planed. A
safety-conscious operator always stands to one side of
the machine, out of the path of the moving stock.
Abrasive Belt Planer
The abrasive belt planer is a machine that uses a
large abrasive belt to remove material from the surface
of wood to smooth it and reduce the board’s thickness.
The abrasive belt planer is a safer machine than the
knife-blade planer. The abrasive belt planer eliminates
kickback and the problems related to removing and
sharpening knives. In addition, abrasive belt planers
generally have lower overall maintenance costs and
are less noisy than knife-blade planers. Abrasive
planing can improve lumber yields up to 20 percent
by eliminating product defects caused by knife-blade
planers. The machine shown in Figure 21-3 is a high-
production abrasive belt planer used in furniture
manufacturing. It can handle large parts at speeds of
up to 80 feet per minute. On this planer, the stock
is fed into the infeed section of the first unit, which
planes the top side of the stock. The wood is then
carried on a conveyor to the second head, which
planes the bottom of the board.
Abrasive belt planers have heavy sanding belts
instead of conventional metal knife-blade cutters
used in other planers. Abrasive belt planers can be
purchased with belts from 12″ (30 cm) to almost 10′
(3 m) in width. Machines of this type are constructed
with any number of planing heads to meet high-
volume production requirements.
Figure 21-4 shows the interior of the same
machine. Note the vertical planing belt exposed on
each head. At first glance, you might think that a
sanding belt would wear out quickly in a production
environment. If the machine is used properly, this is
far from true—the belts are tough and will last for
a long time. However, if you try to take too large a
cut with one pass, or if you attempt to plane stock
with nails or other metal fasteners, the belt will tear.
Tears or holes shorten the life of the belt, leading to
premature failure.
Planing can also be done using hand planes.
Removal of stock on the edges is a relatively simple
process. Planing of end grain can result in the blade
digging in, and chipping or breaking off the edges
of the workpiece. The proper procedure is to hand
plane from the edges working toward the center.
Jointing
The jointer is a machine that can improve overall
quality of a workpiece by effectively complementing
the work of the planer and circular saw. For example,
even if stock is purchased with both face sides planed
from the mill, it is still necessary to true-up one edge
on a jointer before proceeding.
Figure 21-3. This large abrasive belt planer surfaces the
top side of the wood in the first unit and the bottom side in
the second unit. It is used for high-speed production planing
in a furniture factory. (Timesavers, Inc.)
Figure 21-4. This is the abrasive belt planer shown in
Figure 21-3 with covers removed to show roller drive
mechanisms that carry the abrasive belts. Note that the belt
is on top in unit at right, and at bottom in unit at left. This
permits surfacing both sides of the stock in a single pass.
(Timesavers, Inc.)
Belt on
bottom
Belt on
top