[log in to unmask] wrote:
> And, I believe Henry Phillips invented the P-Head in the 1930's for 
> power drills used in car manufacture.   Why wouldn't someone have 
> invented it earlier?  Is it because the advantages of P-Heads are much 
> reduced in non-power use?  That's the way it seems to me.
>  
> Christopher

Slotted screws and their requisite screw drivers have always been a lot 
easier to make by hand (and perhaps also by machine) than the Phillips 
design (I could probably fashion a Phillips driver by hand but I'm not 
sure how they get the phillips head on the screw, cast or forged that 
way??) but the slotted driver needs to be centered to drive the screw 
properly.  Then there is the legacy factor of using what you know and 
are comfortable with (slotted coming first as you say).

With power drivers, its best to have some type of centering bit.  It 
seems that Robertson came before Phillips with a square tapered design 
but it hasn't been marketed well internationally although it is fairly 
common in his native Canada.  Supposedly the taper helps secure the 
screw to the driver very well so starting and driving them is much easier.

Besides the screw heads, it is a lot easier to mess up a Phillips driver 
unless care is taken while using them and restoring a slotted driver for 
use once buggered up (by someone digging out paint or trying to open a 
stuck paint can lid, e.g.) is easier than reshaping a Phillips driver 
(which can't do either of the previously mentioned tasks well any way). 
  Because of the risk of damage, drill guns usually use hardened bits 
and they tend to be treated as a disposable commodity.

Where is the Barton/Walters collection of drivers these days?  Maybe 
their examination will reveal more information.

Your turn,
Screwy

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