Posted by Paul Valente on 11/10/2019 16:35:46:
I’ve actually got the piece down to the base of the taper.
All I really need is an exact length for the threaded portion.
Which piece do you have? The hexagon part that lives in fresh air or the 1/4" UNC part threaded into the headstock? If the part threaded into the headstock through the aluminium cover is not there (i.e. the female threads in the headstock are clear), it might be a good idea to look inside the headstock to make sure it has not worked its way in there.
This is a situation where you will be really happy to see the broken off end of the fastener in the casting.
A countersunk fastener's length is always given from top of head to end of screw so the length of the threaded part itself is not usually given. Your assumption is correct, so what you have to do is determine the countersink angle. I did not tell you this as I cannot remember if UNC is 90 degrees or 82 degrees. Simply remove one of the other screws nearby and copy it.