boomer

Apart from the obvious (slightly different angles, extra small slots on the Pozi etc.) - what is or are the real differences between these two kinds of screw?

Is one better than the other?
Which system is used by generic cross-headed screws?
Are there any more +type screws that i need to know about?

mb (fed up with using the wrong shaped driver!)

cement man

I dont really know but i think the Posidrive has got a performance pack

Dave T-S

Basically the differences are as you say. Probably the most noticeable is the the screwdriver does not "cam out" of the slots on Pozidriv as easily as it does on Philips.

Pozidriv is basically a euro thread, USA and Japan are still mostly Philips.

You can tell a Pozi screw head easily by the four thin grooves in between the slots, and the inside corners of the X slot are chamfered off rather than being sharp.

Subaru unfortunately seem to use some screws that are a mixture of both.......!

ChrisB

boomer

Dave,

any idea what the four "grooves" actually do??? It seems that there are (at least) 3 different pozi sizes, although my Dad (for whom i bought a pozi screwdriver set some 30 years ago) seems to think that one size fits all. Surely there must be a "Pozi web-site" somewhere??

Chris,

you better let "msbuilder" know about the correct spelling of Philips!! Nice piccies though

mb (still wondering)

Olly

Basically a Phillips screwdriver has 4 prongs and a Phillips headed screw has 4 slots. A Posi screwdriver has 8 prongs, and a Posi headed screw 8 slots. Hence more surface area contact, therefore more torque can be generated without slipping out.

A Phillips screwdriver will turn a Posi head and vice versa. But then so will the end of a bread knife.

MichelleWRX1994

Oi boomer, I want your photos

CrisPDuk

Olly, why are you still wondering why I won't have a kitchen of you, wood spoiler.

Brendan Hughes

Isn't it something to do with the fact that Pozi is more suited to automated assembly? Something about the driver locates in the head better, or has less chance of jumping out, or generally doesn't require a human technician to come along and unjam and restart the assembly line. Hence why Pozis are used in mass production products.

No idea where I got this from, but thought I'd throw it in...

boomer

Well for the benefit of all you "screwdriver fans", i managed to find the following web-site that has some useful info...

http://homepages.ihug.co.nz/~grevers/screw.htm

Sounds like the Pozi is best!

mb

Dave T-S

Boomer

There are at least four Pozi sizes (#1 to #4, unsurprisingly ).

The four chamfered points on the inside corners of the "X" are wedges to stop the driver camming out.

The four thin grooves that run from the centre out on top of the screw in between the driver slots are purely to identify it is a Pozi screw and not a Philips.

Dave T-S

PS - if you try and use a Pozi driver in a Philips screw and vice versa as mentioned above you will just destroy the screw, driver, or both. They are NOT interchangeable!

Olly

Dave, the four extra radial marks on a Posi screw head running from the centre point do actually serve a purpose, and are not just for identification purposes. Examine a Posi screw carefully and you will find that the 4 marks are actually grooves running downwards between the four main prongs to give a total of 8 slots on the screw head, matching the 8 prongs on a Posi screwdriver.

You are absolutely right: the two are not interchangable. Turning a Posi head with a Phillips driver or vice versa usually results in a chewed head or mangled driver.

Boomer: Posi's do indeed rule. We buy screws by the 100,000 at work. 90% are posi heads, 9% torx, 1% slotted brass for very fine hinges in cabinet making.

Dave T-S

Olly

I agree with you, the extra four narrow slots inside the "X" do go down inside the head of the screw and are the wedges that help stop camout, but it is where they go across the flat part of the head of the screw they do nothing, it is only for ID purposes to tell it is a Pozi screw.

CharlieWhiskey

The forming of the extra notches in the head actually work hardens it making it less likely to be damaged in the vulnerable area