Since the slotted head wood screw went into decline we have now got various fillips type bits for screwing all the different types of these screws. My question is, what do all the different numbers and letters mean on the screw driver bits mean. I know there are different types of heads on the same size screws for some reason but why?
Wikipedia has a bit about the different types of crosshead screwdrivers: https://en.wikipedia.org/wiki/List_of_screw_drives#Cruciform_types
Basically the sizes are pretty meaningless, just abstract numbers increasing with driver size. The letters distinguish between the popular types (Phillips, Pozidriv and Supadriv). Their slightly different profiles are developments of the original idea which is to make the driver self-centering, tolerant of not being absolutely vertical to the screw and able to apply lots of torque without climbing out of the screw head.
It’s usually overlooked but the screws themselves a have little diagonal notches on the head to show what driver they’re designed for.
All the screws (cross head) on our cars are JIS not Phillips. Japanese Industrial Standard (JIS) are different to Phillips. The good news is you can buy these screwdrivers easily enough. However, I’ve never owned a JIS screwdriver or bit but have always managed to undo any screw ive needed to with my own toolkit made up of different pozi/Phillips screwdrivers?
Barrie
I purchased a set of JIS screwdrivers a few years ago as I have a Japanese motorcycle with screw heads apparently made out of cheese. On difficult screws, like those on the handlebar-mounted hydraulic reservoir, a Philips screwdriver will quite simply chew the head to destruction… I’ll leave you to guess how I know this!
The reason that the JIS are better is described in the link -
http://ruggedroads.co.uk/epages/00cbb604-5d1c-407e-8207-580e14387ec5.sf/en_GB/?ObjectID=7575847
I’ve also got a set of JIS socket type screwdriver bits for the bike as they’re far easier to pack away given the lack of storage space on the bike.
The JIS screwdrivers are a bit pricey in comparison to Halfords jobbies but they’re so worth it!
I agree with Bettabuilda, except the screws holding the soft and hardtop retainers need a special screwdriver. Strange but true, I found one in a hardware shop in France, where they were most helpful. Neither a Pozi or Phillips head but star shaped instead. These screws appear to be made with a safety head.
My local mechanic has a set of drivers of this type, but they are right angled, (like an Allan key) so you can apply max pressure. Forgot to ask where you can get them, or what type of driver they are.
Best type of screw and driver I’ve found was in Canada, where they have a Robertson square inset head and matching square ended driver. They make more sense, but sense was apparently never a priority in Europe, just style. Generally used for wood and self tapping screws. Drivers are colour coded, so easier to pick up at the right time.
Industrially, general use is the Allan head, an easy product to use, though the square head is easier. Getting the right sized key first time has always been a problem for me, a case of trial by error. I’ve gone through several sets, they always disappear when you want the right one. ( a lot pinching I’m afraid.)
[quote=Martin Young]
Wikipedia has a bit about the different types of crosshead screwdrivers: https://en.wikipedia.org/wiki/List_of_screw_drives#Cruciform_types
Basically the sizes are pretty meaningless, just abstract numbers increasing with driver size. The letters distinguish between the popular types (Phillips, Pozidriv and Supadriv). Their slightly different profiles are developments of the original idea which is to make the driver self-centering, tolerant of not being absolutely vertical to the screw and able to apply lots of torque without climbing out of the screw head.
It’s usually overlooked but the screws themselves a have little diagonal notches on the head to show what driver they’re designed for.
[/quote
I didn’t know that last bit you wrote so will check it out now. Thank you for your reply
Those are “Torx” screws. I increasingly see manufacturers using tamperproof versions with a protruding pin in the centre of the recess. The smaller sizes of Torx are really useful if an Allen key chews up a stuck screw head. If you get just the right size of Torx they bite right into the corners of the Allen head and let you apply enough force to get it loose.
If anyone regularly deals with phillips/pozidrive screws I recommend snap-on bits - you know, the ones that fit in all the hex interchangeable bit screwdrivers.
I use this one most regularly…
https://store.snapon.com/Phillips-174-ACR-174--Bit-Phillips-ACR-2-P662784.aspx
To deal with all the most common, size 2 phillips and posidrive screws. When the situation is marginal this bit is as good as it gets.
Certainly, in combination with my snap-on ratchet screwdriver, another tool I would not be without.
As probably already mentioned the easiest way to differentiate phillips from pozi-drive is that pozi bits and screws have a blunt end where phillips are sharp pointed. Phillips also have flutes on the diagonals on their bits where pozi is smooth. For most applications makes little difference - if the bit fits in the slot it will undo but on the margin you have to get it right or do a lot more work.
Sounds like Torx - more common now but rarely found in a typical toolkit!
Good Story About Torx.
Around 2004 or 2005 a local auction house had a PC to sell that would not bootup, a Compaq sort of triangle shaped PC base unit.
I had bought a screwdriver set on a little wall stand from LIDL that had these weird star type screwdrivers in it on the front of the stand that I never used as I used the Philips and Posidrive screwdrivers in the kit!
I would look at the star drive drivers every now and then and then do what ever I was doing next.
Our plumber friend was talking to his mate an auction guy who was saying “that is only worth £5 if it does not boot but £100 if it is working”.
My plumber friend said “I will get Eddie to sort that”.
The PC arrives and I find out you need to press a reset key inside the case, but the case was fastened by these weird star shaped screws!
I go through all my tools and nothing fits, therefore I phone Compaq and ask how do you get the side off as I cannot move the fixings and the guy on the other end of the phone advises you need a “Special Compaq Engineer” who has the special tools to open the PC.
The light bulb came on when he talked about a “Special Compaq Engineer”. I was well aware they were PC techs and nothing special at all. My nonsence detector turned on and I said these screws are as special as a " Special Compaq Engineer".
Walked out to the garage, went straight to the weird star drivers on the wall stand and low and behold the side was off the PC.
These days I have a full set of both internal T and external E Torx keys but apart from some drive shaft, Suzuki hub and cylinderhead studs they are probably used say once or twice a year on cars a bit more often on small electrical household items.