INCRA Ultra 24 - Manual (Page 12)

12
FIG. 22
Equally spaced
3 /
8
" box joint
FIG. 23
Make the cuts on the
top half of Fig. 22
JOINT MAKING
3
3
/ 8
"
2
5
/ 8
"
1
7
/ 8
"
1
1
/ 8
"
3" 2
1
/ 4
"
1
1
/ 2
"
3
/ 4
"
0"
Backing
board to
prevent
splintering
Wooden
handscrew
clamp
FIG. 24
Make the cuts on the
bottom half of Fig. 22
Backing
board to
prevent
splintering
Wooden
handscrew
clamp
Make cuts at the following scale
settings (use floating scale):
0",
3 /
4
", 1 1 /
2
", 2 1 /
4
", 3", 3 3 /
4
"
Make cuts at the following scale
settings (use floating scale):
3 /
8
", 1 1 /
8
", 1 7 /
8
", 2 5 /
8
", 3 3 /
8
"
2
1
3
NOTE: If you have purchased the INCRA Master Reference Guide &
Template Library, it is not necessary to read this section on joint making.
You'll find the Reference Guide covers this topic completely.
Three important operations take place when using your INCRA JIG
ULTRA for joinery at your router table:
1. Setting the router bit depth of cut
2. “Centering” the bit on your workpiece
3. Cutting the joint
Again we will use a step-by-step approach to make using and
understanding these operations easy. Let’s start with a box joint.
Box Joints
You’ll want to begin this exercise by cutting your stock to length and
width. Use
3 /
8
" thick stock and cut (4) boards to 3 3 /
4
" wide x 6" long.
The joint you will be making is an equally spaced 3 /
8
" box joint so you’ll
also need a 3 /
8
" straight bit.
Set the depth of cut
Install the 3 /
8
" straight bit in your router table and set the depth of
cut to slightly greater than the thickness of your stock.
“Center” the bit on your stock width
Use the “centering” method described on page 9 to find the
center of the board. After you have found the center, slide the
extra 1 /
32
" floating scale to position the 1 7 /
8
" mark directly under the
hairline cursor. On some smaller router tables you may find the 1 7 /
8
"
mark will not reach the hairline cursor. To remedy this, simply move
the hairline cursor to the rear of the base. See Fig. 12 on page 8.
Cut the joint
Clamp two of your boards to the INCRA Right Angle Fixture with a
backing board as shown in Fig. 23. The backing board is used to
prevent splintering as the bit exits the cut. Make cuts at the scale
locations shown on the top half of the drawing in Fig. 22. Make sure you
are using the floating scale in Step 2. After completing the cuts, flip the
boards end-for-end and repeat the same cuts. Now clamp the remaining
two boards with a backing board to the INCRA Right Angle Fixture as
shown in Fig. 24 and make cuts at the scale locations shown on the
bottom half of the drawing in Fig. 22. “Sneak up” to the first cut (0") in
several light side-by-side passes to avoid splintering the edge of the
stock. (This is just good router table technique.) When you have
completed the cuts, flip the boards over and repeat the same cuts.
You have just completed your first INCRA box joint. With a little
practice, it’s really quite easy. You’ll notice in Steps 2 and 3, we installed
and used the
1 /
32
" scale to locate the various cuts. When you later begin
using the joinery templates from the optional INCRA Master Reference
Guide & Template Library, they will be used in the same way. In fact,
the INCRA joinery templates are simply “scales” which have had all the
marks you don’t need left off. Just find the center of your stock, slide the
suggested “center cut” on the template under the hairline cursor, then
make “A” cuts on two of the boards and “B” cuts on the remaining two.
Too tight or too loose?
Check the fit of the pieces. If the joint is too tight or too loose, the
problem is the bit, not the INCRA JIG. An oversized bit will create a
loose fit. An undersized bit will create a tight fit. The best fit will be
found by using a straight bit that is just slightly oversized, which is the
way that most good bits are manufactured. To loosen a tight fitting
joint, you can micro adjust the fence backward about five thousandths
and then re-cut one of the series of cuts. CAUTION: Remember,
whenever cutting with a straight bit, that the bit manufacturers recommend
that you cut no deeper than the diameter of the bit in a single pass.
3
3
/ 4
"
3
/ 8
"