Craftsman 351.219071 Instruction Manual page 23

Figure 38 Figure 39
,
When making next penetration, leave a gap
between the first and second holes. See Figure 38.
4. Once the desired length of the mortise is achieved,
go back and chisel out the remaining gaps. This
will ensure a smooth, clean mortise. See Figure 39.
NOTE: Bluing of the chisel is not indicative of a dull
chisel, but a combination of friction and resin buildup
on the cutting faces of the chisel. A dull chisel can be
detected by the amount of excess force required to
complete a cut.
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