I decided to put into action something that I
had planned to do for a long time. From my late father’s estate I
inherited a cast-iron foot that presumably belonged to some kind
of chemical laboratory equipment. Not being impressed with the
commercial ‘third-hands’, I kept this piece of cast-iron with the
view of converting it into a tool with less and better
controllable degrees of freedom. Also just having a pair of
cheaply made alligator clamps didn’t add to the useability of the
commercial tool that, in consequence, spent most of its life on
the shelf. I also inhereted a good quantity of pre-war quality
alligator clamps.
The cast-iron foot was de-rusted and a proper seat for the
bar-clamp had to be filed – I could not find a way to clamp the
piece to the table of my milling machine. The foot then was primed
and spray-painted in my favourite ‘bottle green’ (RAL 6007).
Working predominantly on small-scale ship-models with tiny parts,
I sized the tool appropriately. The main bar is 6 mm steel and the
two pillars are 10 mm aluminium. I actually prefer steel, but in
this case working with aluminium was faster on my small machines.
The arbors for all the clamps are 4 mm steel rod. The diameter of
4 mm was chosen, as the alligator-clamps have sleeves that are
meant to be pushed over 4 mm-banana-plugs.
Thinking about the likely kind of applications, I made a pair of
small sprung clamps from steel, a pair of larger toolmaker-style
clamps (excellent idea by Michael, btw) in aluminium to be used
for soldering, a pair of small hooks in 0.5 mm piano-wire for
rigging tasks, and a pair of collect-chucks.
The collet-chucks are commercial products from China with ten
collets that clamp from just over 0 to 3.2 mm. I thought this
might be a good idea for clamping wires and perhaps ropes safely
without distortion or marring. They were so cheap at 2.50€ for a
chuck with ten collets that there was no point to make them
myself.
I also plan to make set of clamps from bakelite for soldering, but
have not received the ordered material yet.
The thumb-screws are also bought in, as I have local source here
in Paris that sells them for one Euro a piece, which is not
exactly cheap, but good value considering how much time I would
have spent making them myself.
Rather than bakelite
(which is phenolic
resin filled with wood flour and which is essentially
isotropic) I received
‘Novotext’ rods. Novotext is a composite of phenolic resin and
cotton fabric.
This is bad and good news. The bad news is that its
temperature resistance is
lower than that of bakelite and, hence, the clamps cannot be
used for soldering
as originally envisaged. The good news is that Novotext is
much less brittle
and more elastic than bakelite because the cotton fabric takes
up the strain,
as does the steel in re-enforced concrete. The material mill
and turns well,
and you can cut threads in it. So the design is the same as
that for the metal
clamps. In the end I got some nice clamps out of it, nicer
than the wooden ones
I attempted.
