John & Galoots,

Thanks for the McFeely's square drive information John.

PL Robertson also manufactured and sold, under his name, the screwdrivers 
for his screw. The tips of these Robertson manufactured drivers are formed 
to the same shape as the screw socket shown in the patent, including the 
matching pyramid tip and sides tapering about 10 thou of an inch in an 
eighth of an inch run.

From my observation, it's a safe bet that these days not many 
Robertson/square drive screwdrivers are manufactured to the original 
standard.


Marv Paisner
Kootenay Lake, BC




-----Original Message----- 
From: John Ruth
Sent: Wednesday, February 20, 2019 2:07 PM
To: Marvin Paisner
Cc: Stager, Scott P. ; Listserv Oldtools
Subject: Re: [OldTools] Screw Head

Marv, and inquiring Galoots

I just went down to the shop and opened a clearly-labeled original box of 
McFeely’s flathead square drive screws. I hold one in my hand as I tap out 
this message!

The McFeely’s square drive recess IS NOT the same as shown in that Robertson 
patent.

There’s no chamfer angle at the mouth.

The bottom of the recess is not a neat pyramidal shape as shown in the 
patent. Rather, it looks hemispherical
in nature.

The recess itself has “vertical” walls.

I think the Robertson is the better design in terms of getting the driver 
quickly seated into the hole.

John Ruth 


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