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6. To eliminate chip-out of the workpiece when
performing cheek cuts, an auxiliary wooden backup
board can be fastened to the backstop (G) Fig. 23, with
two wood screws through the two pre-drilled holes (N).
Fig. 24 illustrates a backup board (P) fastened to the
backstop.
7. A block of wood may also be fastened to the vertical
support plate (R) Fig. 24, through four pre-drilled holes
(S) to prevent the saw blade from contacting the jig in
certain set-ups.
OPERATION
This jig is intended to perform the cheek cuts of the
tenon only. The cheek cuts are usually performed before
the shoulder cuts, which are usually cut on a table saw
using the miter gage.
WARNING: KEEP HANDS ON JIG HANDLES
WHEN PERFORMING CUTS (SEE FIGS. 30 & 31).
CAUTION: DISCONNECT MACHINE FROM POWER
SOURCE.
STRUCTURE OF A MORTISE
AND TENON JOINT
Fig. 25, illustrates the parts of a simple or "blind" mortise
and tenon joint.
A. Structural Shoulder
B. Cheek
C. Cosmetic Shoulder
D. Mortise
E. Mortise Walls
Start by laying out the mortise and tenon onto the
workpieces a shown in Fig. 26, but keep the following
items in consideration when laying out the joints:
• To avoid premature joint failure, avoid locating a tenon
in a disfigured part of the grain such as a knot, for
unpredictable movement of the joint may occur.
Always use straight, flat, common-grained stock as
shown in Fig. 25.
• The tenon will shrink in width, away from the mortise
walls, possibly revealing the mortised hole; therefore,
when possible, tenons should have shoulders on all
four sides, two structural and two cosmetic, to
conceal the mortised hole when wood movement
occurs.
N
P
E
9
G
Fig. 23
S
R
Fig. 24
A
C
D
Fig.25
Fig.26
B
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