tim   .


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.   hunkin





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.





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