(32 threads / inch) * (1 in / 25.4mm) = 1.2598 threads / mm
1/1.2598 = 0.79375 mm / thread (pitch)
That's not even CLOSE to 0.6mm pitch
(42 / 25.4) = 1.65354 threads / mm
1/1.65354 = 0.6048 pitch
I think you meant 42 TPI not 32 :)
The problem is he has 6-40 screws that the hardware store incorrectly thought it was (that don't fit) and 6-42 isn't a standard size - if it was, it would probably work, as there wouldn't be that many threads engaged, so the error would be minimal.