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Tip
#10
Mortise & Tenon
Click
the following for a printer friendly
version of Tip - Pg. 1-3,
Pg. 4-5
Mortising
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Figure
8-5. All of the following joints can be made by
working with mortising bits and chisels: (A) through,
(B) keyed, (C) haunched, (D) blind, (E) loose wedged,
(F) three-way, (G) twin, (H) notched, (I) open-faced,
(J) concealed haunched, (K) through wedged. Click on
image to see larger view.
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All the
joints shown in Figure
8-5 can be made using the mortising accessory.
Position
the workpiece on the table and depress the chisel to do the
cutting. Use only enough pressure to keep the bit cutting
(Figure 8-6).
Pressure required will vary with the size of the chisel and
the hardness of the wood. Softwoods such as pine cut easily,
while hardwoods such as maple require considerably more pressure.
If you can't make the cut without exertion, it is probably
because the edges on the bit and/or the chisel are dull.
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Figure
8-6. Work with the correct speed and use only enough
feed pressure to keep the bit cutting. Mortising cuts
need a heavier feed than simple drilling, but if you
must really lean on the feed lever, check the chisel
and bit for sharpness.
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The rip
fence/worktable V-block arrangement can be used to hold round
workpieces. Be sure to mark the workpiece so the cuts will
begin and end on the same line (Figure
8-7).
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Figure
8-7. The fence/table V-block arrangement can be
used to hold round workpieces for mortising. Be sure
to mark the workpiece so the cuts will begin and end
on the same line.
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Figure
8-8. Two factors that may spoil a mortise: (A) Chisel
tends to lead off twoard the cavity already formed,
and (B) workpiece tends to drift away form the chisel
as the cut is being made. Click on image to see larger
view.
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Two factors
which tend to spoil a mortise are illustrated in Figure
8-8. To eliminate these, cuts should be made as shown
in the order given in the second detail of the drawing. The
general rule is: Always make the end cuts first. Start with
1/4 n deep cuts, never less than threequarters of the full
width of the chisel. This may not be possible on the last
cut, but keep as close to it as you can. Repeat until desired
depth is achieved.
Avoid
narrow shoulders. The chisel will drift away, leaving a tapered
side. Many workpieces split because tenons are forced into
mortises with slopping sides. If necessary, use a smaller
chisel.
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Introduction
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