I'll add/correct this OP as we go.
I'll only list size, not length or head type, as this largely depends on the exact model, and length is tricky if you carry the knife tip down, possibly use custom scales and/or clip, and don't want to damage the washers (I don't want to be responsible if you do ). For example, the Manix 2 has T8 heads, the Para 3 has T6. Fluted Ti Military has shorter clip screws than the G10 version, single liner Military has Philips heads, MXP screws are longer than stock, etc. So this is the only list that can be generalized, IMHO:
- US #2-56
- Japan: M2.3 x 0.4
- Taiwan: M2 x 0.4.
- Paramilitary 2, Para 3, steel-lined Manix 2 / XL, steel-lined Native 5:
- Scale screws are 4-40, 1/5 inch long, 100 degree T8 flat-head
- Pivot screws are 6-32, 1/5 inch long, 100 degree T10 flat-head
- The new G10 and plain Ti Military (2017+) Scale screws are 4-40, 1/5 inch long, 100 degree T8 flat-head (same as Paramilitary/Manix)
- The new Military has two 8-32 T15 button-head Pivot screws (.235 inch long).
- The old plain Ti and double liner G10 Military has 2-56 T6 Scale screws (.185 inch long)
- Both old and new fluted Ti Militaries have T8 button head scale screws, I believe 4-40, not sure about the length (anybody?)
- The old double liner Military single Pivot screw is also 8-32 T15, but a little longer (.263 inch).
- The classic single liner Military single Pivot screw is also T15, but has a finer thread than newer Militaries (anybody?)
- Others ?