Thanks to all who responded about the ROBERTSON drive screw. Even though
we use these in our fabrication shop I did not know the proper
terminology. They are readily available south of the 49th from
industrial supply houses. They show up on my list as SQUARE RECESS
drive. If you ask for them in U.S. houses ask for square drive or
SCRULOX. They really are superior to the cross head or phillips pattern.
If you want the best of both worlds, believe it or not, there is a
Combination Square/Phillips drive screw that will accept either drive.
Kind Regards,
David F. Darby
Missouri
P.S.
Two more drive shapes for the list and I won't add any more:
Square nut drive
Flattened End Hanger Screw Drive
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