On Tue, 02 Jul 2013 16:18:02 +0000, Safeman
wrote:

I need to source 90 of 9/16 UNC flush headed countersunk bolts/screws
overall length 2" and 10 of the same but overall length 2.5"

It doesn't matter what type of drive they have and preferrably threaded
the whole way, I could live with 1/2" unthreaded shank.
Any more than that I guess would be acceptable, just a lot of thread
cutting for me to do....

Anybody help, I have run out of ideas...
9/16" is not a standard SAE size. What is this on???
14mm 2mm pitch is a standard and fairly close. A DIN7991, metric
coarse ISO 90 degree is 366-487 in 50mm length from Spae-Naur