There are two kinds of Philips wood screws. The better ones fit the
screwdriver like hand and glove, stay on it and maintain the
direction. The "other kind" do not, they wiggle out and are a huge
pain to use to start holes in awkward positions, etc.
It is not really magic and it is clear why this is the case -- the
philips hole on the better ones is deeper and has a better fit.
My question is, rather, what is that mating called, if I order wood
screws online at mcMaster-Carr, what should I be looking for?
Are you sure you're not confusing "posidriv" with "cross head"? ;-)
Cross-head *is* a Phillips head.
Posidriv looks sorta like it but has the additional radial markings to
differentiate the Posidriv head.
Robertson is certainly an improvement over Phillips. I prefer Torx, but
they're usually more expensive. Anthing larger than about a #8x3 I usually
spring for them, though. I don't use all that many so the extra cost isn't
On Friday, May 27, 2011 4:16:59 PM UTC-7, Jim Stewart wrote:
Err.... actually, Philips is a tradename, and it's licensed
so there's probably some genuine standards commitment
there. Philips markings on a screwdriver used to mean
some assurance of quality (maybe still does).
It's also a callout.
I can show you any number of unambitious and
acceptable assembly drawings and bills of
material that call out Philips screws.
Tradename doesn't matter. I can call out a
Philips screw just as I can call out Delrin
or or Meehanite as a material.
Or maybe I've missed your point...
===========Sounds like you may be fighting the Pozidriv v Phillips wars
all over again.
Phillips drivers have an intentional angle on the flanks and
rounded corners so they will cam out of the slot before a
power tool will twist off the screw head. The Pozidriv
screws and drivers have straight sided flanks.
The Pozidriv screwdriver and screws are also visually
distinguishable from Phillips by the second set of
cross-like features set 45 degrees from the cross. The
manufacturing process for Pozidriv screwdrivers is slightly
more complex. The Phillips driver has four simple slots cut
out of it, whereas in the Pozidriv each slot is the result
of two machining processes at right angles. The result of
this is that the arms of the cross are parallel-sided with
the Pozidriv, and tapered with the Phillips.
This design is intended to decrease the likelihood that the
Pozidriv screwdriver will slip out, provide a greater
driving surface, and decrease wear. The chief
disadvantage of Pozidriv screws is that they are visually
quite similar to Phillips, thus many people are unaware of
the difference or do not own the correct drivers for them,
and use incorrect screwdrivers. This results in difficulty
with removing the screw and damage to the slot, rendering
any subsequent use of a correct screwdriver unsatisfactory.
Phillips screwdrivers will fit in and turn Pozidriv screws,
but will cam out if enough torque is applied, potentially
damaging the screw head. The marker lines on a Pozidriv
screwdriver will not fit a Phillips screw correctly, and are
likely to slip or tear out the screw head.
posidrv bits and screwdrivers
(Amazon.com product link shortened)
and a whole bunch more
Let the group know what you find as there are most likely
others with the same problem.
-- Unka George (George McDuffee)
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).
As others have pointed out, you are probably not using the correct
driver on the what you assume may be a Phillips head screw.
Drop that style screw altogether and use square head drive screws. I
switched over 25 years ago.
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