Measured with mics they measure 3mm as they should and they are tempered wire so as strong as the stock shaft
I do have a lathe but normally just use the drill press as I don't want to get grindings on the bedway.
I use the Dremel disc grinder and on some I just grind a flat on the back and use a wheel collar which I trust more.
Couldn't count the number of shafts I've made for my flying buddies.