[ROVERNET - UK] P6B nuts and bolts specs

Vern Klukas vern at inkspotco.com
Mon Nov 5 16:34:15 GMT 2007

The Phillps head was invented in the 30s, and was designed to cam out 
as Ken says. The problem, from a manufacturing standpoint, was that 
the recess was often burred by the bit when it rode out, requiring 
replacement. In the end, industry moved to torque limited 
screwdrivers that either stalled or released the drive, rather than 
depending on the design of the Phillips.

Both Phillips and Pozidriv are US inventions, and it is curious that 
Pozidriv has had so little success in North America.

As for Pozidriv being the defacto standard int he rest of the world, 
Europe perhaps but Phillips (actually the Japanese variation) are 
more common in Asia and certainly in electronics manufacture.

The Canadian Robertson (square recess) is better than either Phillips 
or Pozidriv (and Torx too) but under-appreciated in the world. I 
think it is because the square somehow has a unsophisticated look to 


>I don't understand Patrick's remark about Pozidrive.  I believe it is
>the standard screw-head everywhere in the world except the US, and until
>I moved from Britain to the US (working in design of electronic
>equipment which certainly contained screws), I had in fact never heard
>of Philips screw heads.  All my screwdrivers from the period were/are
>Pozidrive.  As far as improvement is concerned, that depends on the
>application.  I believe that Philips heads were developed for mass
>production using electric or air screwdrivers; when you are doing up a
>screw, you don't want to stall the screwdriver (at least, not those of
>WWII vintage), so when the screw gets tight, the bit rides up out of the
>head.  That is of course fine the first time during assembly, but makes
>it much more difficult to undo the screw subsequently, or to do anything
>with a normal hand-held screwdriver.  In contrast, Pozidrive
>screw-driver bits, and of course the corresponding screw heads, have
>straight parallel sides (no taper), so there is no tendency to ride out
>and thus no need to apply downward force to hold the bit into the screw.
>That is also very convenient for getting screws into inaccessible
>places, since a screw will remain on the bit; Philips screws fall off
>the bit.
>Ken Gundry
>-----Original Message-----
>From: rovernet-bounces at lyris.ccdata.com
>[mailto:rovernet-bounces at lyris.ccdata.com] On Behalf Of phing
>Sent: Saturday, November 03, 2007 8:12 PM
>To: rovernet at lyris.ccdata.com
>Subject: Re: [ROVERNET - UK] P6B nuts and bolts specs
>Thanks . I've been hauling a Posidrive screwdriver around in my tool
>box since 1972 ,. I knew I would need it one day . Posidrive was a
>British GKN " improved Phillips" type screw head . It became a world
>beater , just like Beta max and 8 track tapes !
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Vern Klukas                             I'm a little . . .
Inkspot Type & Design
vern at inkspotco.com

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