Here are the details.
The coupling should be made from steel road (about 20mm diameter). The
total length should be 40mm. The first 20mm should be lathed down to
accept a 5/16 thread (this is how the head will attach). The other end
should have a 5mm hole drilled down to a depth of 10mm (for the motor
shaft). 5mm in from the motor end,a 1/8 threaded hole should be drilled
at right angles to the motor hole. The 1/8 threaded hole should extend
all the way to the motor hole (for locking the motor shaft with a small
bolt.
-- Dave Everett Email: deverett nospam at idx.com.au (c) 1996 - Copyright remains with the author unless explicitly stated