28 SERVO 08.2015
as I progressed. I basically modeled the wooden hand
loosely on my own hand, with each finger segment roughly
the same size as my own. If you’re looking to make
something similar, I’d suggest you measure each segment
of each finger of your hand to get a scale model.
I’m glad I didn’t have a 3D
printer, as drawing, cutting, drilling,
gluing, throwing out, and starting
again adds to the enjoyment and
creativity! Some good music or a
good documentary to listen to in
the background, all the requisite
tools, enthusiasm, and plenty of
time, and you’re good to go!
To start with, I chose a one
meter length of 10 mm diameter
dowel to act as the finger
segments, cutting them to suit my
sketches using my faithful Dremel
Multipro. The blackened ends of
the finger joints you see in my
You Tube video were from the
Dremel cuts — basically burning the
wood as it cut.
Now, I needed knuckles, so I
began looking in hardware stores
for cheap but effective hinges which
could join the finger segments
together and enable them to move.
I looked at small hinges, curtain rod
connectors, scissors, and other
potential donors, but it wasn’t until I
was in the local supermarket and I
saw a tea-infuser hanging on the
wall that I knew I’d hit paydirt (or hingedirt)!
They were $2 each, and each infuser had two pressed
metal ‘hinges’ — two pieces of metal with a hole and pin
that had been shot peened at one end. So, I bought 15 of
them for $30 (to the eye-raised surprise of the checkout
operator!), and low and behold oodles of infusers awaited
their fate (Figure 2).
I checked all of the hinges, and out of all 30 only about
18 moved smoothly and didn’t jam. I mean these are
average quality pressed steel and
not designed with tight tolerances
in mind or to flop around
The 18 that passed the test
were more than enough for the
three knuckles I needed for each
A visit to the local
haberdashery store and I found
suitable thick cotton thread for
tendons and some very small metal
eyelets to be transformed into
tendon guides (Figure 3).
I also found some narrow
black elastic (like you would find in
a pair of pants) which I wanted to
use on top of each finger joint to
provide resistance — to return the
finger to an ‘open’ position
This elastic would also be
applied to the thumb assembly
The ‘opening’ and ‘closing’ finger movement is actually
termed ‘flexion’ and ‘extension.’ Bending the fingers toward
the palm is flexion, or what I’m calling closing the finger;
bending the fingers out straight away from the palm is
extension, or what I’m calling opening the finger.
In between the finger segments (top of the
hinge/knuckle), I used pieces of cut silicon tube. This
provided an improvised form of cartilage to stop the finger
segments bending back too far, and to also provide a small
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Figure 4. Elastic strip to
provide resistance when
Figure 2. Tea infusers provided the hinges (knuckles).
Figure 3. Eyelets to guide tendons.
Note the 'cut-and-ready' pair at right.