The Posi-drive screw

=A0 London SW

I remember when it came as a revelation to me (when I moved into my own house) that there were two types of "Phillips" screwheads, and that the reason that my Dad's old crosshead screwdriver kept on chewing up screwheads was that they were actually pozi screws instead. Single most important lesson I learned I think!!

Matt

No, but that is the only sensible way to read the two pieces in conjunction (unless they are lying and flag or c*ck-waving). The other sources I looked at pointed to them having patented it, and not GKN.

It says that GKN purchased the world-wide patents, which strongly suggests GKN weren't inventor.

True enough. So we have a self-serving source suggesting it was Phillips who invented Pozi, versus no source suggesting that GKN did - other than your bald assertion that it was so, and Geoff's recollection of what his dad's mate claimed to have done (far be it from me to suggest that he might have been waving his, erm, flag).

I really don't understand this bit about using an impact driver with screws - surely not!? Or is an 'impact driver' not what I think it is.

To me an impact driver is a bottle-shaped tool which you hit with a hammer, providing torque to loosen (or tighten I suppose!) a screw, nut or whatever.

The world's moved on - the term is now more commonly used to refer to this sort of thing:

The other thing of course is that ordinary Pozidriv screwdrivers wear out quite quickly, as woodscrews are made from hardened steel. So if you really must use a manual one perhaps finding one that suits you but takes replaceable tips. I've got a bag of old blunt Pozidriv and Phillips ones waiting to be ground down into something useful. ;-)

Indeed - but the name's been pirated. Should be called a power impact driver or summat to differentiate from the real one. But their principle is similar - they use a form of kinetic energy to whack the screw round. And are a pretty successful device.

Probably not. This may help:

Same here, as in:

It's when the screw won't come out because you fcked the head with the wrong size or type of screw or too lazy or can;t find the correct one so bodge it. ;-)

Also a handy word when you've done yourself an injury and are told not to use the nasty C. word as it's insulting, you just say I didn't say that, I shouted 'cam out' it's a technical term you wouldn't understand luv. :)

Indeed. Same principle really. Suppose we should call them 'Impact Screwdrivers'

Obviously not :-)

Impact screwdriver. 12v drill driver about 25Nm torque, 12v impact screwdriver 135Nm torque. Or about 6 hours labour saved on a big deck.

I've been using mine all week, kitchen units, wardrobes, shelves. I was a bit concerned about the fixed speed as well. but as you say the clutch is brilliant. Put over 50 cam lock studs in a flat pack 3 door wardrode earlier this week - easy peasy.

I added a Wera Magnetic Ringmagnet bit holder to my kit;

They've usually got an 1/2" square drive so they can be used with sockets as well. Indeed there are special strong sockets supplied with the one I have.

Other thing I noticed in B&Q was a Bosch mains drill that called itself 'impact'. It had a standard chuck so must have been just an ordinary hammer drill.

I've seen that before but couldn't work out what actually it does - another crappy Screwfix description unfortunately. Is it just the round black part which attaches to your own bits? And how does it retain screws?

David

It wouldn't remove a couple of ordinary wood screws holding my floorboards down. Just clicked away. ;-) My ancient B&D screwdriving mains drill did, though.

Not sure I believe that 135Nm - that's nearly 100 lb.ft which would shear just about any wood screw and certainly the No10 I was trying to remove. For reference, that's tighter than most car wheel nuts.

I wasn't refering to the 7.2v Makita which is 17Nm, but to the 12v makita.

Thats what Makita quote in the spec for the 6980FDWAE - actually 125 Nm.

I have had that happen with my 18V driver (145 Nm) once or twice... usually when you have a longish fastening that is held tight at the end, so there is enough torsional elasticity in the screw to absorb the impact and then spring back before the next. You need sustained torque to shift these.

Which an impact driver (well the larger ones anyway) will happily undo for you ;-)

A short bit is inserted into the end and protrudes by about 5mm. There is a very strong magnet inside which holds a pozi screw. Then the blue/black sleeve slides forwards and the magnet contacts the entire head of the screw. Works very well indeed, as it should for the price.