"Mys Terry" wrote
Scotty doesn't even realize that the phillips head screws on BSA's
were, in fact, Whitworth screws. After he would strip the head, he
probably had a little trouble trying to force those SAE or Metric
threaded replacements into the Whitworth threaded holes.

They may not have been Phillips - there is a similar pattern that uses a
screwdriver with a sharper point (Reed & Prince??). If you use the latter
screwdriver on a Phillips screw you will strip the head slots because the point
doesnt allow the driver blades to fully engage the screw head slots. No need to
ask how I know this or why I like to replace the Phillips screws in my bikes
with Allen screws.