English
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down, the blade stalls and the motor reaction drives the
unit rapidly back toward the operator. If the blade becomes
twisted or misaligned in the cut, the teeth at the back
edge of the blade can dig into the top surface of the wood
causing the blade to climb out of the kerf and jump back
toward the operator.
Kickback is more likely to occur when any of the following
conditions exists.
1.
iMPROPER WORKPiECE sUPPORT
a. Sagging or improper lifting of the cut off piece can
cause pinching of the blade and lead to kickback.
b. Cutting through material supported at the outer ends
only can cause kickback. As the material weakens it
sags, closing down the kerf and pinching the blade
(Fig. O).
c. Cutting off a cantilevered or overhanging piece of
material from the bottom up in a vertical direction
can cause kickback. The falling cut off piece can
pinch the blade.
d. Cutting off long narrow strips (as in ripping) can
cause kickback. The cut off strip can sag or twist
closing the kerf and pinching the blade.
e. Snagging the lower guard on a surface below the
material being cut momentarily reduces operator
control. The saw can lift partially out of the cut
increasing the chance of blade twist.
2.
iMPROPER DEPTh OF CUT sETTing On sAW
a. To make the most efficient cut, the blade should
protrude only far enough to expose one-half of
a tooth as shown in Figure I. This allows the shoe
to support the blade and minimizes twisting and
pinching in the material. See the section titled
Cutting Depth Adjustment
.
3.
BlADE TWisTing (MisAlignMEnT in CUT)
a. Pushing harder to cut through a knot, a nail or a hard
grain area can cause the blade to twist.
b. Trying to turn the saw in the cut (trying to get back
on the marked line) can cause blade twist.
c. Overreaching or operating the saw with poor body
control (out of balance), can result in twisting the
blade.
d. Changing hand grip or body position while cutting
can result in blade twist.
e. Backing up the saw to clear blade can lead to twist.
4.
MATERiAls ThAT REQUiRE EXTRA ATTEnTiOn
a. Wet lumber
b. Green lumber (material freshly cut or not kiln dried)
c. Pressure treated lumber (material treated with
preservatives or anti-rot chemicals)
5.
UsE OF DUll OR DiRTY BlADEs
a. Dull blades cause increased loading of the saw. To
compensate, an operator will usually push harder
which further loads the unit and promotes twisting
of the blade in the kerf. Worn blades may also have
insufficient body clearance which increases the
chance of binding and increased loading.
6.
liFTing ThE sAW WhEn MAKing A BEVEl CUT
a. Bevel cuts require special operator attention to
proper cutting techniques – especially guidance of
the saw. Both blade angle to the shoe and greater
blade surface in the material increase the chance for
binding and misalignment (twist) to occur.
7.
REsTARTing A CUT WiTh ThE BlADE TEETh
JAMMED AgAinsT ThE MATERiAl
a. The saw should be brought up to full operating
speed before starting a cut or restarting a cut after
the unit has been stopped with the blade in the kerf.
Failure to do so can cause stalling and kickback.
Any other conditions which could result in pinching,
binding, twisting, or misalignment of the blade could cause
kickback. Refer to the sections
Further Safety Instructions
for All Saws
and
Blades
for procedures and techniques that
will minimize the occurrence of kickback.
Cutting Depth Adjustment (Fig. A, H, I)
1. Hold the saw firmly and loosen (clockwise) the depth
adjustment lever
4
and move shoe (
5
, Fig. A) to obtain
the desired depth of cut.
2. Make sure the depth adjustment lever has been
retightened (counterclockwise) before operating saw.
For the most efficient cutting action, set the depth
adjustment so that one-half tooth of the blade will project
below the material to be cut. This distance is from the tip of
the tooth to the bottom of the gullet in front of it. This keeps
blade friction at a minimum, removes sawdust from the cut,
results in cooler, faster sawing and reduces the chance of
kickback. A method for checking for correct cutting depth
is shown in Figure I. Lay a piece of the material you plan to
cut along the side of the blade, as shown, and observe how
much tooth projects beyond the material.
Fig. H
4
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Fig. I
