Straight from my email
They used to call it 13/16-32, but the outside diameter of the feedneck is slightly smaller (usually 0.807-0.808). If you want the published specs on that, check this link here
(be careful with that website, they limit the number of times you can visit a page per day, so if you surf around too much they will lock you out for a few hours....)
Anyway the theoretical size that SP uses for their female threads on the bodies was 0.784" diameter. I don't know the tolerance for it but it was probably 0.002 or less. Later when they moved to the "NXT" feedneck threads, they were also 32 threads-per-inch but the diameter was increased by about 0.060. Pretty pointless in my opinion, since a threaded feedneck is a threaded feedneck. Making it bigger didn't change much.
I once had a tap for the feedneck but I quickly wore it out by tapping the threads by hand. The custom tap cost around $100 for two of them (I had to grind one of them down into a "bottoming" tap so I could actually finish the threads). The real way to do it is via threadmill but that's not something that anyone can do so easily....
On 5/17/2011 7:51 PM, Brandon wrote:
hey andy, just wondering if you happen to know the thread for the Ion feedneck.