I had a think about how I was going to create some registers on the camshafts for the timing pulley grub screws and still maintain the correct orientation. I had in mind some sort of jig that I could use to lock the camshaft and crankshaft orientation, move the pulley out of the way and create the flats at the witness marks left by the grub screws. Amongst other things major problem was the ends of the camshafts, that held the ignition magnets were just not long enough to accommodate the clamp and get they pulley out of the way.
I had already added a second grub screw at 90deg to the original so it occured to me I could remove one grub screw and insert a drill down the hole to put an indent on the shaft. Replace the grub screw and do the second.
The problem with that would have been the possibility of damaging the thread if I used a twist drill.
I’ve used 6ba grub screws for which the tapping drill size is 2.3mm I have some 2mm piano/music wire so decided to try a D bit. The advantages being that I could grind the end to the 90deg of the tip of the grub screw and there would be less chance of damaging the threads.
The brass collar is a stop set for a 1mm indent in the 4mm camshaft.
I had thought that piano wire is capable of being hardened and tempered like silver steel. It proved not to be the case. Case hardening with “Cherry Red” (Kasenit equivalent) did the job.
The indents were done ‘in situ’ so the timing didn’t get disturbed. The drill vice used to clamp the two shafts together and stop them moving. It was all very easy in the end
Pete