I make my own. The outside diameter is 42mm, the internal is the pipe diameter (15mm, 22mm, 28mm etc). There are basically two ways of doing it:
a. Turn down outside diameter to 42mm, drill / bore internal diameter to required size (ream if possible). Cut in "half" lengthways to leave one 21mm high with the flat face downwards. Other part is waste.
b. Drill / bore centre to 10mm. Use a slitting saw in a mill and cut exactly in half lengthways. Super glue both halves together. With a four jaw chuck, drill / bore ream inside diameter, turn outside diameter. Split halves, minimum waste.
Not as simple as it sounds, but the costs of aluminium bar to make a full set by method B is less than the purchase cost of a single pair.
a. Turn down outside diameter to 42mm, drill / bore internal diameter to required size (ream if possible). Cut in "half" lengthways to leave one 21mm high with the flat face downwards. Other part is waste.
b. Drill / bore centre to 10mm. Use a slitting saw in a mill and cut exactly in half lengthways. Super glue both halves together. With a four jaw chuck, drill / bore ream inside diameter, turn outside diameter. Split halves, minimum waste.
Not as simple as it sounds, but the costs of aluminium bar to make a full set by method B is less than the purchase cost of a single pair.
