Assembling the key

 
Again I'm going to keep this really simple, the next task is to fit the pivot onto the base, I have used a spare block of Acetal I had in my junk box, I would have normally used a block of shaped Mahogany but out of that at the moment, a base can be anything really and most prospective key builders should have no problem sourcing a nice base, basically the job consists of mounting the pivot on the base by drilling two 5mm holes in the pivot base and then countersinking them with the tool shown below, then the holes are enlarged under the base to accept the nuts to tighten it all on, beware when enlarging the hole the drill doesn't grab into the hole and spin the base out of control, a firm grip is required whilst drilling
When the pivot is fixed to the base the arm is assembled and a drill passed through the tension adjuster hole to mark the position for a 5mm hole to take the tension spring, this is drilled out and enlarged under the base to take a small pin that will hold the spring in place when fitted, next job is to make the spring tension adjuster, this is just a 1inch brass bolt with the head cut off, one end of the adjuster is filed flat on two sides and a small 1mm hole drilled into it, this where the tension spring will be attached, it is a small fiddly job and you may need to make a couple of attempts to get it right, the key can now be tested in as much as the contact block can be rested on the base so the contact spring sits between the gap adjuster and resting post, the contact block is not fitted at this stage as the key has to be "tuned" this comes next with final assembly with lots more pictures that will clarify many points that may not be clear at the moment.