Silly screws

[Pamphonica]

Or you can always use special-purpose fasteners like these.
Happy Christmas
Jeremy

[G6Tanuki]

They're quite commonly found on electrical/mechanical assemblies (engines, gearboxes. motors, pumps etc) for attaching serial-number/model/specification-plates: their difficult-to-remove-ness being a positive advantage in such situations.

[AC/HL]

That's quite different to the original premise of this thread though, keeping unqualified fingers out of equipment, whilst allowing servicing as required. There's usually no (legal) requirement to remove identification details.

[Richard_FM]

I remember one of my friends did an apprenticeship with British Rail in the 1990s & used to bring home some odd bits & pieces.

One was a bolt where the head could be sheared off, leaving a conical shank that would need some working on to get it removed.

Another was a bolt that would spead glue over the threads while it was being tighened, needing a lot of torque to remove it.

Apple were fond of using torx bolts on the early Macs, which lead to the tools needed being called Mac Drivers.

I remember in another thread someone mentioned GPO telephone infrastructure using odd sized BA fittings to make them less vulnerable to tampering, as these sizes were not common.

[Herald1360]

Originally Posted by Richard_FM

One was a bolt where the head could be sheared off, leaving a conical shank that would need some working on to get it removed.

Sounds similar to the steering lock shearbolts mentioned above. (Un)happy contortionist sessions with a hammer and centrepunch come to mind, though these days a left handed drillbit in a cordless driver would probably be quicker!

[AC/HL]

Once Again, nothing silly here, a vital safety feature. Members of this forum may well be competent, only they know, but there are many others with beliefs well in advance of competence, they walk amongst us, always have!

[suebutcher]

What about silly nuts? Saab used tri-wing nuts to prevent access to the ignition lock on their cars.

[woodchips]

Ah ha, no one come across the Bristol Spline wrenches?

Used in US equipment during and after WW2.

They look like Allen screws until you realise they are actually splines, now you know why you can't get the knobs off US radios!

Bristol still make them, I bought direct three sets of the smallest sizes, been invaluable.

[McMurdo]

there's a lucrative market in power screwdrivers/nut runners in the manufacturing world. Many manufacturers of these tools have introduced proprietary designs of screw head. In some cases, each screw-tightening on the production line is logged in a database for correct torque and number of turns, so that a problem with a loose screw can be traced to an individual workstation.

For example wheel nuts on cars, screws holding covers on stuff that would expose live parts if they came off, etc.

Whether that explains the 'tri-wing' screwdriver I had to buy to take apart a Nintendo tv game is another matter (the little girl had optimistically inserted a fisher-price music box disc into the cd slot and jammed it).

Or it could be the built-in obsolescence genie at work.

[TonyDuell]

I mentioned Bristol Spline screws back in post 23

[vidjoman]

Originally Posted by McMurdo

Whether that explains the 'tri-wing' screwdriver I had to buy to take apart a Nintendo tv game is another matter.

I first found Tri-Wing screws on Jukeboxes from the 1950's. Used where an external screw was needed for access but made it hard for casual persons to break-in to steal the records.

[Richard_FM]

I've heard of non-standard screws on games consoles to deter hackers from gaining access to the innards.

[G6Tanuki]

Originally Posted by TonyDuell

I mentioned Bristol Spline screws back in post 23

And me in #38

Bristol stuff is fascinating.

[mole42uk]

As a resident, I’d say Bristol is fascinating.

[pmmunro]

Originally Posted by suebutcher

What about silly nuts? Saab used tri-wing nuts to prevent access to the ignition lock on their cars.

I've never seen these as much of an obstacle, possibly because they're quite big and never, in my experience, too tight. Possibly that makes them silly anyway. It's not the ignition lock which they protect, it's the reverse gear lock, A SAAB speciality chosen as an alternative to steering locks which did not seems a good idea to Trollhätten logic.

Originally Posted by Philips210

There's a another type of screw that is a cross between standard slotted and Phillips which I think is called a Modulo screw and is found in many electrical consumer units as in the RCD and MCB screw terminals. That is probably a very sensible idea to help prevent cam out when tightening. The corresponding screwdriver is like a Phillips type but with one of the blades longer than the other.https://cpc.farnell.com/productimage...L13405-500.jpg

This is more worrying than mere manufacturer protectionism. I suspect that the fires which gave rise to non-flammable consumer units in Amendment 3 of the 17th Edition Wiring Regulations were often caused by people using the wrong screwdriver on such screws. Too many either don't know, or won't accept, that there is a significant difference between Phillips and Pozidriv and this leads to damaged fasteners and tools.

The tool Symon links to seems to take a very good grip when used as intended with at torque screwdriver.

Possibly manufacturers of electrical equipment, certainly items big enough like consumer units, should have to label the equipment to state the type of screw slots used. Much as I think that the Pozidriv slot is a good design I fear it has failed because of the false interchangeability with Phillips. The best solution would probably be to move to TORX fasteners for all electrical equipment which needs torque set screws.

PMM

[turretslug]

Originally Posted by pmmunro

Too many either don't know, or won't accept, that there is a significant difference between Phillips and Pozidriv and this leads to damaged fasteners and tools.

Ooh, you've touched on one of my pet hates there!- even folk who title themselves "engineers" glibly use the one where they ought to be using the other. I keep a few good quality Posidriv screwdrivers with nice crisp profiles and a few Philips ditto tucked away, they're kept well away from use by ham-fisted 'erbets.

(Another pet hate being flimsy plastic consumer units- whoever let them on the market deserves fifty lashes).

[GMB]

Never mind Phillips vs Pozidriv, what about Pozidriv differences?
I have a set of Pozidriv drivers, and another set calling itself the same but actually different.
I despair of this.

[Oldcodger]

I remember a technical meeting at a firm I worked at, where engineers were told to go out and buy a bottle of bright red nail polish, and once a bit of kit was repaired, paint the screws to prvent customer tampering,so geat was the problem.

[Herald1360]

That won't prevent tampering only show that it has occurred. RS used to flog it as "Tamper Evident Seal" but now they sell some epoxy stuff for the same job which seems to be a thread lock as well.

Edit: After looking at the safety sheet it looks like the same old.......

[FrankB]

When I first was the Torx with the pin in the center, the bits were N/A here. I just used a punch and snapped the pin out, then used a Torx driver to remove the screw.
Made a good nut off microwave oven repair for a few years.

Their is a NASTY screw used in the Hamlin TV cable converter boxes I ran into.
Its oval. Barely, but a special driver is needed to remove then, and they come in different sizes. I just can't remember the name of them right now.
The cable company had just 1 driver for dismantling them to repair them. I did over 1000 of those boxes. I did make a bit that worked by using an old RCA plug socket, removing the center and slightly deforming it to an oval. It worked just fine too.
When that wore out, some tubing from the hobby shop, deformed, worked OK too.