Saw - Special Operations
Forming Simple Inlays
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In the table
saw mode, the Mark V can perform a variety of operations. Kerfing,
or thinning out, allows you to bend wood without steaming. Kerfing
can also be used for a decorative effect. You can also cut coves,
inlays, and raised or pierced panels. Warning: Many of the special
operations require the removal of the upper saw guard. Whenever
the upper saw guard is removed, keep the lower saw guard in place
and work with extreme caution.
Whether in a
home workshop or a commercial establishment, most woodworkers often
find it necessary to bend wood to a particular shape. It may be
needed on a furniture project-the apron on a drum table or round
stool-or on other projects like a garden arbor with an arched top
or a doorway with a semi-circular upper structure. Commercial establishments,
of course, can bend wood to almost any shape by steaming it or using
chemicals to make it flexible. In the home workshop, you don't usually
have the special bending equipment, but you can still do an impressive
amount of wood bending just by working on the table saw and using
either the kerfing technique or a thinning out process. You must
use straight grain lumber for any bending.
A good amount of wood bending can be done mby using the kerfing
technique. Kerfs can extend the full length of the workpiece
or be confined to an area.
The most popular
method of bending wood without steaming is by kerfing (Figure
4-1). What this method accomplishes is a reduction in stock
thickness, while allowing room (between the cuts) so the wood can
bend back on itself. The depth of the kerfs and their spacing are
the important factors and are variable. Deep kerfs, closely spaced,
allow the sharpest bends (Figure
The kerf spacing can be veried, depending on the sharpness
of the bend. (A) The kerfs should be more closely spaced in
the sharpest bend area. (B) Greater specing is sufficient
wher bend begins to straighten.
To bend wood
with minimum loss of strength, proper kerf depth and spacing should
be determined using a simple test.
Make a sample
kert in a test piece of stock that you wish to bend (Figure
4-3). In 3/4" stock try a kerf that is 5/8" to 11/16" deep.
Position the test piece, kerf side up, on a flat surface and hold
it in place with a clamp on the right side of the kerf. The distance
from the kerf to the edge of the surface on which you have placed
the work should equal the radius of the bend you need. Lift the
stock at its free end until the kerf closes and then measure the
amount of lift at the edge of the table. This tells you the distance
required between kerfs.
this test to determine, at least as a start, the kerf depth
and the spacing you need to make a particular bend. Click
on image for larger view.
Use a miter guage extension to mke the kerf spacing guide.
The distance from the pin (8d nail) to the slot automatically
spaces the kerfs.
Since work like
this calls for a considerable number of kerfs correctly spaced,
you should work with a kerf spacing guide like the one shown in
Figure 4-4. After
you have secured the guide to the miter gauge, cut a saw slot through
it and then drill a hole for a nail to serve as the guide pin, spacing
it away from the slot a distance equal to the required kerf spacing.
Make the first kerf with the workpiece butted against the guide
pin. The distance between the remaining cuts is automatically gauged
by placing the last kert over the guide pin (Figure
4-5). When the kerfs must be cut in a central area of the stock,
make the first cut without using the guide.
By placing the last kerf over the guide pin, the work is accurately
positioned for the next cut.
the number of cuts, first find the circumference of the circle that
will form the corner of the project. Divide this number by the total
number of corners on the project. This will be the length of one
corner. Divide the length of the corner by the total width of the
saw kert plus the spacing between the kerfs. This will give you
the number of cuts you'll need to make. The formula for this is:
Circumference ÷ Number of Corners = Corner Length
Corner Length ÷ (Kerf Width + Kerf Spacing) = Number of Cuts
Example: Calculating the number of cuts for a 12" dia. circle, used
on a four corner project, with a saw kert of 1/8", and kerf spacing
= 3.14 x 12" = 37.68"
37.68" ÷ 4 = 9.42"
9.42" ÷ (1/8" + 3/4") = 9.42" ÷ 7/8"(.875) = 10.77 or 11 cuts
is complete, bend the wood slowly until the curve you need is achieved.
Wetting the wood with hot water (even if you must soak it awhile)
will help the bending process. Also, use a tie strip, tack-nailed
in place, to hold the part's shape until it is permanently attached
on an assembly.
You can form
irregular curves if you do the kerfing on both sides of the stock
and/or vary the kerf spacing. When the kerfing is exposed, veneers
may be glued in place to conceal the cuts. If you're working on
an outdoor project, coat the kerts with waterproof glue before making
the bend. Wood dough or putty can be used to fill the crevices.
When the work has been correctly sanded and finished, it will require
a close examination to reveal the method used to make the bend.
Wood can easily be bent when you reduce its thickness in the
bend area. This is the "thinning out" technique.
out, the stock's thickness is reduced the full length of the bend
area (Figure 4-6).
In effect, you are producing a length of veneer which is an integral
part of the wood. The thinning out can be done with the dado or
molder head. It can also be done by resawing the stock on the bandsaw.
This method permits very sharp bends; but, since the veneer area
won't have much rigidity or strength, corner blocks should be used
to provide structural strength (Figure
4-7). Thinned out sections that have the wood grain running
lengthwise will be stronger than those where the grain runs crosswise.
Thinned out areas, even kerfed areas, cna be reinforced by
using corner blocks. Click on image for larger view.
Coves can be produced on the table saw by passing the work
obliquely across the saw blade. It requires many passes and
the cutting should be done with a combination blade that has
Coving is a
unique table saw operation in that the work is fed obliquely across
the blade (Figure 4-8)
It is a lengthy process because the shape is achieved by making
numerous passes with the saw blade's projection increased by no
more than 1/16" each pass. Coving can be done with the table set
at 90° to cut a circular cove or with the table tilted to cut
an elliptical cove. If a narrow edge cove is needed, either cut
it on a wide piece of stock and cut away the scrap when coving is
complete or cut the edge cove from a center cove. Warning: The
cutting action is essentially a scraping one, so trying to rush
by using more than 1/16" blade projection is not safe. The blade
will tend to cut rather than scrape and the action will cause the
workpiece to move away from the guide strip and kick back. The first
thing to do is
Construction details of a parallel rule that will be used
to determine the position of the guide strip. Click on image
for larger view.
make the parallel
rule fixture that is diagram-med in Figure
4-9. The angle of the cut determines the width of the cove.
Set the distance between the fixture's long legs to equal the width
of the arch you want (Figure
4-10). Next, set the saw blade's projection to equal the depth
of the cove and then place the fixture so its long inside edges
just touch at the front and rear of the blade. With the parallel
rule so positioned, clamp a guide strip to the worktable at the
angle determined by the rule (Figure
4-11). The guide strip must be positioned on the infeed side
of the blade only so the cutting action forces the stock into the
guide strip. The distance between the guide strip and the saw blade
will determine whether the cut will be centered, off center, or
on an edge of the stock.
The distance between the long legs of the fixture should equal
the width of the arch.
The saw blade's projection should equal the depth of the cove.
The guide strip's position is gauged by the parallel rule.
Start the work
by setting the blade's projection to no more than 1/16". Use a push
block to hold the workpiece firmly against the guide strip and make
the pass very slowly. Pay special attention to how you place and
use your hands. Warning: Coving is done without the upper saw
guard In place so work with extreme caution. Use a feather board
and push block to support and guide the workpiece. Never cut edge
coves that will be wider than half the stock width. Avoid placing
your hands over the blade or in line with the cut. After the
first pass, increase the blade's projection another 1/16" and make
a second pass. Continue in this manner until you have arrived at
the arch's depth.
Edge coves are also possible. Make the passes very, very slowly.
This kind of
cut can be made on stock edges (Figure
4-12), but be sure of hand position and that the cove is no
wider than half the stock width. With all coving operations, you
can clamp a second guide strip to the table parallel to the first
one. The distance between the strips equals the width of the stock.
Thus you have a "road" along which you move the stock. If you wish
to speed up the operation, you can do so by cutting kerfs to remove
the bulk of the waste material (Figure
The bulk of the wast removal can be accomplished by making
repeat passes with the saw blade.
Some of the applictions for workpieces that were formed by
Coving is a
useful technique because it can be used to produce components like
those shown in Figure
4-14. Shapes like those in Figure
4-15 are possible if the coving is done on pieces that have
first been lathe turned. The coves that are formed are not true
semi-circles; this could only occur if the work were fed across
the blade at right angles to it. However, some work with a drum
sander or hand sanding is usually sufficient to true up the arch.
Shapes like this are possible by cove cutting after the workpiece
has been turned to a cylinder on the lathe.
Here are some kerfed molding designs.
One way to individualize
your work is with original molding designs like those in Figure
4-16. Most of these are done by using the kerfing method described
for wood bending or variations of it. Thus, the kerf spacing guide
used for bending kerfs can also be used for moldings. Instead of
making the kerts on only one face of the stock, the work is turned
over for each new cut (Figure
4-17). A fixture that is used for finger joints may also be
used should you wish to produce wide notches using the dado head.
Another way to produce exclusive moldings is to strip-cut pieces
from stock that has been surface contoured with the molder.
Kerfs for moldings can be done using the kerf spacing guide
used for kerf bending. Invert the stock and turn it end-for-end
for each cut.
Examples of pierced panels. The openings are the result of
intersecting cuts that are made on opposite surfaces of the
done on the table saw by running intersecting cuts on opposite surfaces
of the stock. When the projection of the saw blade is a bit more
than half the stock's thickness, openings in the work result where
the cuts cross (Figure
4-18). The overall pattern is affected by the kerfs as well
as the openings, so it is important to visualize the results before
doing the cutting. It's wise to go through the procedure on scrap
material. By using a simple guide like the one shown in use in Figure
4-19, the kerfing can be done at an angle, which adds another
dimension to the technique. Piercing can be done with a regular
saw blade or with a dado head for wider cuts. Warning: Piercing
is done without the upper saw guard in place so work with extreme
Piercing can also be done by making angular cuts. Since most
work of this type is too large to be handled with a miter
gauge. It is necessary to make a special notched guide so
the passes can be made safely and accurately.
Some simple inlay work can be done by cutting surface kerfs
and then filling the cuts with strips of contrasting wood.
The idea in
forming simple inlays is to cut kerfs (Figure
4-20), with a saw blade or dado head, and then fill the grooves
with a contrasting wood (Figure
4-21) that is cut to fit. Working in this manner, you'll have
a tight, professional looking fit when the inlaid strips cross each
other. Warning: Inlays are formed without the upper saw guard
in place so work with extreme caution.
You can inlay wider strips if you do the kerfing with the
dado accessory. Click on image for larger view.
Cut all the
kerfs that run in one direction and inlay the strips. Then cut the
crossing kerfs. The second set of inlay strips will form perfect
joints where they cross the first ones. Always cut the inlay strips
so they are a bit thicker than necessary. You can sand them, after
installation, so they will be flush with adjacent surfaces.
panels for room doors, cabinet doors, or wall pan-eling will be
easy with a fixture that you can use with your table saw.
straddles the rip fence and will hold your stock securely as you
cut the bevels for your panel.
Construction dtails of the raised panel fixture. Click on
image for larger view.
Make the fixture
(Figure 4-22) by
first cutting all parts to size. Drill the adjustable clamp holes
where shown 2" apart. Use glue and screws to assemble all parts
except the clamping strip. Glue fine-grit sandpaper onto the face
of the fixture. Note: This fixture can double as a tenoning fixture.
Insert the workpiece against the back-up strip and cut a tenon on
the end of the workpiece.
To use the raised panel fixture, tilt the table 5° to
15°. Place your stock in the fixture, secrue the mounting
screws as close to the panel as possible.
To use the fixture,
tilt the table 5° to 15°--the greater the tilt, the narrower the
bevel. Use a carbide-tipped blade for a smoother cut. Place your
stock in the fixture, put the clamping bolts as close to the panel
as possible, and tighten the wing nuts. The sandpaper will also
help keep the panel in place. Position the rip fence on the right
side of the blade. Set table height so the inside edge of the blade
penetrates through the stock (Figure
4-23). Turn off the machine after each pass and reset the panel
in the fixture to cut each side of the panel.