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A large number of people don't seem to realise there's a difference between Posidriv (or Supadriv) and Phillips screw heads and that a Phillips screwdriver shouldn't be used in a Posidriv screw or vice versa. This Wikipedia article explains everything. tinyurl.com/5fuznb
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"Impact driver".
Edited by FotheringtonThomas on 12/08/2008 at 13:19
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The Decline of Civilisation began with the invention of the Phillips screw.
BP, stubborn screws could be cleaned up with a hacksaw or a sharp cold chisel. AP, stubborn screws wreck themselves and the screwdriver.
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Why can't you simply use the hacksaw on the Phillips screw?
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If the screwhead is accessible, I've done this many times.
I agree, stubborn slot head screws are *always* easier to undo than stubborn Pozi / Phillips screws whether it's by chisel or impact driver. I still find it amusing that Phillips heads were designed to force the driver out of the slot to prevent over-tightening. What a ridiculous piece of design!
Has anyone noticed that Torx screws seem to be replacing all conventional types of screw on modern cars? Almost every fixing I've come across on my Volvo, whether it's the pollen filter housing cover, footwell trim, or spark plug / coil cover has a Torx head.
Cheers
DP
Edited by DP on 12/08/2008 at 14:20
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Has anyone noticed that Torx screws seem to be replacing all conventional types of screw
Generally... although when they do strip out the head....! "Allen" bolts are nicer, IMO.
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I still find it amusing that Phillips heads were designed to force the driver out of the slot to prevent over-tightening.
I've not heard that one before. I know a Phillips driver has a tendency to cam out but I thought this was a deficiency in the design rather than being intentional. I understood that Posidriv was aimed at giving a configuration in which the driver didn't cam out, and as such would be superior to Phillips.
Edited by L'escargot on 12/08/2008 at 15:13
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Has anyone noticed that Torx screws seem to be replacing all conventional types of screw on modern cars? Almost every fixing I've come across on my Volvo whether it's the pollen filter housing cover footwell trim or spark plug / coil cover has a Torx head.
Yep. It is all down to the 'no user servicable parts' message sent out by manufacturers.
Same with a lot of household goods as well.
Makes sense in a way - in the past anybody with screwdriver and a sense of mechanical bravado could open something up and 'have a look at it'... which is a disaster waiting to happen on some of the hi-tech stuff about these days, not only in terms of wrecked equipment, but also in terms of potential injuries/electrocutions etc.
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Why can't you simply use the hacksaw on the Phillips screw?
Can use a Dremel with a blade worn down to a small diameter, to cut a slot in a countersunk screw. I did that on some rusted brake disc retaining screws where the cross of the Pozi head was u/s.
Edited by Rich 9-3 on 12/08/2008 at 15:19
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Why can't you simply use the hacksaw on the Phillips screw?
If the head is countersunk you are trying to cut new metal with a hand-held end of a hacksaw blade. With a straight slotted head you are just cleaning out and deepening an existing slot.
Also when tightening a phillips screw the first warning you get that it is too tight is when the screwdriver slips and burrs the screw. Straight slotted screws are tougher.
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Also when tightening a phillips screw the first warning you get that it is too tight is when the screwdriver slips and burrs the screw.
That shouldn't happen too often. Phillips heads haven't generally been used in well-engineered products for yonks.
Edited by L'escargot on 12/08/2008 at 16:14
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the difference between phillips and pozi drive screws...............about 25p a box at B&Q
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when using an electric srewdriver a slotted screw / bit will jump out and mangle the bit of skin between your thumb and finger resulting in blood soaking into the wood that is the very devil to sand out.
A posidrive/philips just goes BRRRRRRRRRRRRRRRRR
Edited by Altea Ego on 12/08/2008 at 16:38
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Nevertheless, I can't stand cross-head screws in woodwork that's "on show". On old cars, I suppose that x-heads weren't invented when they were made!
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At least with an X head when it all goes horribly wrong you have a natural centre to drill into.
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Having designed products where there were 150 screws holding them together, I far prefer Torx over any other screw head design. These were built at 30,000 a year, that's a lot of screwing. With a torx, you put the screw in place, drop the electric screwdriver in and turn on. It doesn't need to be kept aligned like a lotted screw, the bit doesn't jump out like a posi or philips. Far far better than anything else. It's also possible to apply much more torque to a torx screw.
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I prefer torx too. I hate slotted screws.
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I prefer big nails and a bigger hammer fun to apply, torque carefully adjusted by ever smaller taps if required ...
Seriously Torx make sense, very hard to round out, more so than Allen even.
Edited by cheddar on 12/08/2008 at 23:58
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Torx make sense very hard to round out more so than Allen even.
Interesting - for my interest, do you know of a proper engineering resource stating this?
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Interesting - for my interest do you know of a proper engineering resource stating this? >>
No, personal experience only, though you only have to look at A Torx to see that it would be difficult to round out, less so an Allen bolt with a slightly worn Allen key perhaps.
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Interesting - for my interest do you know of a proper engineering resource stating this? >>
It's obvious... draw a hexagon, and a slightly smaller, slightly rotated hexagon within, and then look at the mating faces.
Draw a Torx, and a slightly smaller, slightly rotated Torx within, and look at the mating faces.
Imagine the direction of the Force as a result of applied Torque (i.e. round the circumference of the screw head). In the Allen key the mating faces are roughly parallel to the Force. In the Torx, the mating faces are roughly perpendicular to the Force.
Accordingly to the extent that there is deformation in either the screw head or driver as a result of these Forces, you can imagine that in Torx it is likely to be elastic (i.e. it returns to its original shape following release of the force) arising from the pressure on the surfaces, whereas in Allen it is likely to be plastic (i.e. the deformation is permanent).
Don't believe me? Imagine making an extra 1mm gap between the screw and driver, and then covering the faces of the screw head with a 1mm thick layer of plasticine; with an Allen head it would be rounded out; with Torx it would still work.
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It's obvious... >>
Agreed 100%, well put!
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Hello, M. Fromage; you've been quiet recently.
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>> Interesting - for my interest do you know of a proper engineering resource stating this? >> It's obvious...
While you may be right, that's not actually what I asked...
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I like to consider myself as a proper engineering resource!
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I hate slotted screws.
Me too. Wickes sell some great screws called Easy Drive, each box has its own specially shaped, magnetic driver bit. For use with electric screwdriver the bit sticks into the screw head like glue, you put the screw on the end of the bit and they do not come out until the screw is in place.
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Having designed products where there were 150 screws holding them together I far prefer Torx over any other screw head design. >>
AFEB? ;-)
Yep, particularly if it's a robot that going to be doing the screwing them Torx every time, no cam out.
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Nevertheless I can't stand cross-head screws in woodwork that's "on show".
With Posidriv screws you can fit a neat plastic cover, available in various colours, to conceal the screw head.
Edited by L'escargot on 13/08/2008 at 07:51
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the difference between phillips and pozi drive screws...............about 25p a box at B&Q
I doubt very much whether B&Q sells any screw or bolt with a Phillips head. Phillips heads are obsolescent.
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Phillips heads are obsolescent.
Apart from the millions used by car-makers every week. GKN's Pozi is the rare one on cars.
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