As has been stated above, in the early days we would put the bolts in the freezer and knock them in. That changed when I found the bolt drawings in the RAFM archives.
The bolts were manufactured to a Fit “P” and were cadmium plated except for the “P” fit shank. Mod. No. Spitfire 1485 altered the bolts so that the end of the thread on the bolt was turned down to the root diameter to obviate stripping of the thread on assembly. The split pin hole was drilled during manufacture to align with the slot in the head of the bolt.
Mtl. S2 HTS.
Oversize bolts were manufactured in 0.004″ steps up to +.028″, the next being +.03125.