|TRUING THE SPIDER
the legs of the spider bridge must contact the cone with equal pressure.
Place the spider on a flat surface, like a table saw or drill press table,
and tap the tips of the legs. You want the spider to contact the surface
only at the tips of its legs. If the tips don't touch, or if the spider
rocks back and forth, you will need to gently bend the legs.
Bend a high leg down to make contact by placing a thin wooden shim (1/16"
to 3/32") under the leg at the point where it joins the ring or "web."
While holding the center of the spider down, push down firmly but carefully
with the heel of your hand. Check your progress frequently. Be careful!
The spider bridge is made of cast aluminum, and will break under too much
knows how fragile the spider can be, since he's broken a few himself! He
prefers the delicate pressure of his palm, instead of a hammer, to work
a leg into alignment.
the legs of the spider are uniform, level the tips by moving the spider
back and forth over a sheet of 320-grit sandpaper on a flat surface. Make
pencil marks under each tip, and check your progress frequently by seeing
where the sandpaper is removing the pencil marks.
bridge saddles are typically made of maple, or maple with an ebony cap (like
a banjo bridge). Birch, walnut, boxwood or ebony are also used. The saddles
should be a snug press fit in the spider bridge, but not so tight that wood
is shaved from a saddle as it's pressed into the spider. A drop of
wood glue or super glue in the slot under the saddle will hold it in place
height varies by instrument, but in general a high saddle creates the steepest
string angle, providing maximum volume. Here's how to determine
Install the cone, spider assembly, and coverplate. With a 6-inch ruler,
measure the gap between the coverplate's palmrest and the top of the
spider. Now remove the coverplate and measure the depth of the slot in the
spider. Add these two measurements together, then subtract 1/32". The
result is the optimum height for your saddles. Without strings, the saddles
will almost touch the bottom of the palmrest. Once the guitar is strung
and tuned to pitch, string pressure will compress the cone so the saddles
will pull down to the proper height.
both saddles are inserted into the spider bridge, they should be leveled
with one another. Do this by sanding across the tops of both saddles with
a sanding block or a file. Pencil marks on the tops of the saddles will
show you when enough material is being removed from both saddles, indicating
a level surface. After leveling the saddles, file or sand their tops to
spacing at the bridge is based on player preference, but a common overall
spacing is 2-1/4". Dividing that spacing by 5 gives a string-to-string
spacing of .450". Measure .225" from the center of the tension
screw to get the spacing for the two middle strings. Space the remaining
strings .450" from these. Mark these string slot locations on the saddles.
Each string slot should be just deep enough so that half the diameter of
the string rests in the slot. If the slots are too large, the strings will
sustain poorly and may buzz or rattle in their slots. If they're too
small, they can pinch the string and cause buzzes and tuning difficulties.
After you cut the string slots, finish shaping the saddles by rounding their
ends. This makes string changing easier, and helps keep the saddles from
touching the coverplate.
|ASSEMBLY AND SETUP
the spider bridge to the cone and tighten the tension screw a half-turn
after it makes contact. Place the cone/spider assembly into the guitar,
attach the tailpiece, and install the strings. Don't install the coverplate
yet. Put a small amount of tension on the strings, and check your intonation
by measuring from the nut to the saddles at the first and sixth strings.
For lap-style guitars (Dobro type) these measurements should be the same.
For example, on a guitar with a 25" scale, the nut-to-saddle distance
should be 25" for both outer strings. If these two string lengths aren't
equal, rotate the cone/spider assembly until they are.
setting the intonation, sight down the guitar from the nut to the tailpiece
to be sure all the strings are parallel as they pass through the saddle
slots. Any angle caused by misalignment can damage the cone, and detracts
from tone and volume.
Shift the cone/spider assembly slightly to one side or the other to align
the strings. In extreme cases, alignment may not be possible through side-to-side
movement of the cone/spider assembly. In that case it may be necessary to
move the tailpiece to align the strings. This will require drilling a new
hole for the tailpiece screw.
clamp the tailpiece in place, then remove the tailpiece screw. With the
strings under minimal tension, loosen the clamp and move the tailpiece until
the strings are properly aligned. Mark the new location for the tailpiece
screw. The old screw hole can be plugged with a small dowel, using wood
glue. After the glue dries, carefully cut the dowel flush with the surface
of the instrument. Drill the new hole in the new location.
Once again place the cone/spider assembly into the guitar, attach the tailpiece
and install the strings without putting on the coverplate.
It's now time to adjust the spider tension screw. Tune the guitar to pitch
and play an open string. The note should have a distorted "fuzz tone"
sound. If not, loosen the tension screw until you hear this effect. If you
loosen the tension screw and cannot get this distorted sound, the break
angle from the saddles down to the tailpiece may be too sharp (this can
damage the cone and hamper tone and volume). In this case, the tailpiece
may have to be bent upwards slightly to achieve the proper break angle.
Bend the tailpiece up in small increments and play a string until you hear
the "fuzz tone" effect. (Loosen the strings temporarily while
bending the tailpiece up.)
Now that you've got the "fuzz tone," tighten the tension screw
1/4-turn and play the string again. Repeat this process until the fuzz sound
is gone, then go 1/2-turn more. This should give you good tone and volume,
while avoiding damage to the cone.
all these steps are completed, remove the strings and install the coverplate.
Be careful not to misalign the cone/spider assembly when you remove the
strings. Put the strings back on, and tune the guitar to pitch.