I’ve finished the preparations for bending the ring of 15mm copper pipe I need for my coat stand.
First, I used a 90° router bit to cut a V in the edge of the MDF former.
Then I designed and 3D-printed a roller with a profile to match the copper pipe, and attached it to a pivot bolt in the centre of the former using Dexion-type angled steel strips. The roller can rotate around this pivot, leaving space for the pipe running around the edge of the former in the V groove.
I need something to hold the end of the pipe in a fixed position against the former while the roller is rotated to press the pipe into the V. I’ve used a wooden block with a hole drilled down the middle and then cut into two pieces. The larger piece, with a half-pipe void running down it, is screwed onto the edge of the former with triangular plates I found in the garage – I think we used them to make a long-dismantled futon base in the 80s. I then made the smaller piece of wood wedge-shaped, so it can be pushed into place as far as is necessary to hold the end of the pipe tangentially against the edge of the former.
The final step has been whittling a couple of wine corks down to fit the ends of the copper pipe, and drying out a few litres of builders’ sand in the sun before sieving it to get the lumps out. I’ll fill a generous length of pipe with sand and cork the ends to stop it escaping. This may not be necessary – when a pipe is bent into a fairly large radius with its walls well supported externally, it shouldn’t buckle, but I don’t want to take any chances. Supporting the walls internally with sand seems like an easy, cheap precaution.
I have no idea whether this will work, but it’ll be fun finding out.