In the early days of SSL, the 4 and 6k consoles were fitted with BA screws and some various taptites. Later on, probably from 1985, the 5K, 9K and other consoles used metric fixings. Bear in mind most of this is from memory going back nearly 25 years ago so, please contact me if I have got it wrong!
The channel module 611 screws were 4BA x 5/16" black countersunk pozi screws, the Bargraph versions were 4BA x 1". Small faders in the modules, the 651 035 (?) echo cards plus the 621 Producer panel screws and other front panel fixings were normally 6BA x 1/4 or sometimes even 5/16" black countersunk hex head screws. All of these were chemically blackened with a matt finish (not the glossy version). Some of these were screwed into a custom made ali block which allowed a threaded front panel fixing via a 6BA screw and a provision for a PCB assembly to mount at 90 degrees to the panel (such as the 651 echo card PCB and the tape remote PCB in the 682 panel normally mounted in the centre section).
Other screw fixings for the console metalwork were, I think, a normal screw for the front fader buffer trim and maybe a 2BA bolt for the penthouse meter trim (along with a strip of ali perhaps to act as a spacer in both locations) plus 2 BA fixings for the end profile triangular shape trim (3 per unit, some involving countersunk or other hex head screws or bolts depending where fitted). 0BA (or use M6 instead) brass bolts were used for both the copper earthing bar buscard fixings for the 0v connections.
The end profile heavy 'banana' shaped trims used a larger screw fixing (2 per unit) which I am not sure about although, I have some here and will measure them but, they were normally a countersunk hex head bolt. George Gilbert, an ex SSL engineer, has been involved in lots of console metalwork extensions and re-fits over the years and knows better than me on this subject (Ggatpumbro@aol.com).
All the console rectangular or more square type isep rail (which now seems hard to find although I have some left) had 4BA insert strips and I think the countersunk screws fitted from the profiles into this were 6.32 taptites. M3.5 screws can also be used as a replacement but take care as the thread is different.
Finally, the module removal tools were basically just a pair of 2BA screws with Sifam knobs fitted so don't be fooled by some expensive versions out there! The earlier patchbay screws had a 4:40 thread used to secure the US Audioline jacks. Later on, SSL fitted custom made mini head hex screws which were used for the Mosses and Mitchell jacks. I will cover patchbays in a different subject in more detail later on. Hope this helps from Jim Lassen.