I use a wide range of metals, woods and plastics in
the things I make. Its fun and really useful to have experience of a broad
‘library’ of materials to chose what to make each part out of. Metals:
mild steel, stainless steel, aluminium, brass, copper, lead, silver and
titanium. Plastics: glass fibre (polyester resin), plexiglass,
polycarbonate, polyurethanes, nylon, delrin, tufnol, foamed PVC, formica,
polypropylene. Woods: hardboard, chipboard, sterling board, birch ply, far
eastern ply, softwood, pitch pine, jelutong, sycamore, mahogany.
However, my favourite materials are simply cheap
plywood and mild steel. They are both under appreciated miracles of the
modern world. Just look at 19th century objects to appreciate
how much more difficult life was without them. Iron structures were all
riveted because the iron of the time became brittle if welded (or bent).
Wood panels could only be made by inserting thin, broad planks in a rigid
frame of thicker timber.
I often build rough prototypes of structures and
mechanisms and these are almost always made of plywood and mild steel. I
usually screw the plywood together so I can change the design and re-use
it. I particularly like black carcass screws – sharp enough to easily
push through ply with a battery drill without any pilot hole and thin
enough to screw into the end grain of most half inch ply without it
splitting. (beware of recent Chinese ply though – the layers are often
not glued together!)
Steel is great for anything that involves moving
parts. Strips of 3mm steel are my ‘Meccano Set’. With all the
essential acronyms that today’s engineering boasts, I called my process
WOGO (Weld On, Grind Off). The strips are tack welded by holding them in
place with one hand and squirting the Mig welder at them with the other
(using it like a glue gun). I don’t use a mask, just screw my eyes
tightly shut before pulling the trigger. If I need to change the parts,
its really quick to grind the weld off with a .8mm angle grinder disk
(another under appreciated miracle of the modern world). Bearings are
simply holes in the steel strips. Steel shafts running in steel have a low
coefficient of friction and last for ages, even if not oiled. Quite often,
once I’ve got a prototype mechanism working well, I just add to the
welds to make them permanent.
My least favourite material is MDF. Absurdly heavy,
impossible to get a good paint finish on the end grain, splits when you
drive screws into the end grain, soaks up water and swells if it gets
damp, and produces horrid fine dust when machined.