Figure 1: Stool overview.
Figure 2: Footprint of legs.
This kit provides the key hardware components to make a height-adjustable
piano stool. It consists of a seat base and threaded shaft assembly and
a steel nut that provide a total seat adjustment of 6". The seat
base and threaded shaft assembly is mounted to the underside of a piano
stool seat, and the 3" long by 1.245" outside diameter nut is
mounted in a hole drilled in a wooden base/cap. The design of the hardware
components is such that there will always be at least 2" of engagement
of the threaded shaft in the nut to prevent the seat from being spun out
of its base. The instructions that follow provide dimensional guidelines
so you can design a stool that suits your needs.
Design Considerations and Assembly
If you are building a four-legged piano stool, the footprint should be
larger in diameter than the seat diameter to reduce the possibility of
the stool tipping over. A three-legged design would require a larger footprint,
since three legs are less stable than four. Our example shown in Figure
1 has four legs, with a 16" diameter footprint and a 12"
diameter seat. Figure 2 gives a top view illustration, showing
that a three-legged stool should have a larger-diameter footprint than
the four-legged stool.
The height of the leg/base/cap assembly should be approximately 2"
shorter than the desired overall height of the piano stool when the threaded
shaft is fully lowered into the nut. The leg/base/cap assembly shown in
Figure 1 is 18", and yields a piano stool that is 20"
high when the threaded shaft is fully lowered into the nut, and 26"
high when it is fully raised.
The wooden base should be large enough to accommodate the nut, which
is 3" long with a 1.245" outside diameter and a 2" diameter
flange. (Our example has a 2" x 2" x 3" long base.) To
drill the hole in the wooden base, you will need a 1-1/4" drill bit
(e.g., spade, forstner, saw tooth) with a shank length of at least 4".
The diameter of the hole should be just large enough for the nut to slide
in easily without having to force it in. An oversized hole, however, may
cause the mounting screws to break out of the sidewalls, preventing them
from fully engaging in the wood.
Figure 3: Nesting template to reduce lumber waste.
Figure 4: Securing nut in the leg/base/cap assembly.
We recommend you test the accuracy of your drill bit in a piece of scrap
wood (of the same material you will use to make your piano stool). Dry
fit the nut into the test piece. If the fit is tight, gradually make the
hole larger with a half-round file or with sandpaper wrapped around a
piece of 1" diameter dowel. When you are satisfied with the fit,
make your base, and drill a hole through the center of the base (repeating
any adjustments that were required to achieve a good fit). It is important
that the hole be on center. While a hand drill should produce acceptable
results, we recommend you use a drill press if possible. Insert the nut
into the hole to test the fit, and make any further adjustments as required.
Remove the nut and set it and the base aside.
The cap in our piano stool example in Figure 1 is 5" diameter
by 1" thick. Drill a hole through the center of the cap (repeating
any adjustments that were required to achieve a good fit). Insert the
nut into the hole to test the fit, and make any further adjustments as
required. Remove the nut and set it and the cap aside.
Note: You may combine the base and cap as one piece in your
piano stool design.
The legs in our example were made with 1" x 8" lumber and cut
with a bandsaw. To ensure the legs are all the same size and shape, we
recommend you make a template. To make the best use of the wood, the legs
may be traced and laid out as shown in Figure 3.
Dry fit the nut, cap and base together before final assembly of the cap
to the base (if two pieces) to ensure the through holes in both pieces
line up with each other. Join the legs, cap and base in such a way as
to produce a secure structure. For the stool shown in Figure 1,
we secured all joints using water-based wood glue (polyvinyl acetate).
We also fastened each leg horizontally to the base, using one screw per
leg, and secured the cap vertically to the legs, again using one screw
per leg. Each screw was counterbored and concealed with a plug.
The diameter and thickness of your piano stool seat should be suitably
sized to support the weight of the intended user. Mark the exact center
of the under side of your wooden seat with a pencil or scribe. Draw a
4-1/2" diameter circle around the center point. Align the seat base
with the circle.
Mark and drill pilot holes, then secure the seat base and threaded rod
assembly to the underside of the seat with four #12 flat-head wood screws.
Glue the nut into the hole in the leg assembly with high-strength slow-cure
epoxy. Mark and drill pilot holes, then secure the nut to the leg assembly
with four #6 flat-head wood screws.
Apply desired finish.
Insert the threaded rod into the nut in the leg assembly. Turn the seat
counterclockwise to raise it and clockwise to lower it.