Holding gunscrews to work on heads

A lot of gunscrews have been messed up or you find a screw thread that fits your missing screw but the head is ‘wrong’?Holding the screw by the threads to do the work is not a good thing.
I collect ‘stand-offs’ from stuff I tear apart, you know, those little risers that are used in assemblies, often threaded on both ends. They come in different dia.s and threads and if you have the right taps you can tap an undersize one to what matches your screw. These become the shank you mount the screw in to chuck up in the drill or lathe to take the load off the screw threads.
For common threads you can sometimes find things in the ‘bins’ at the hardware store. They dont have to be round, a typical nut fits well in a three jaw chuck. The big advantage of these over a nut, or stack of nuts, is the better purchase the chuck has in holding the work (ie, it becomes a fixture).
Of course, if you have the time and tools you could make a set from stock but this has worked well for me.