PSA: DIY Security Screw Spanner Bit (IoT Doorbell Part 1)

Today I wanted to take something apart, and the people that made it clearly disagreed. The screws holding the thing – a doorbell receiver – together were a type of security screw I hadn’t run into before.

I spent a while searching through my screwdriver sets – dozens of security bits I’ve never used before, but naturally that bit I need isn’t one that I have. The screw heads were recessed into the doorbell and hard to see, but eventually I was able to identify them as spanner-head screws (with the help of the handy website here).

The offending security bit.

My initial enthusiasm for disassembling my doorbell was quickly diminishing – I had plans to IoT-ify the doorbell, and not being able to open it up would make this difficult. I searched around online, and figured out a few places locally I could probably but a set of bits – but it’s New Years eve, and that means most places are shut for the next few days. Really not what you want when you’re starting out on a project.

After a bit of thinking, I realised I might be able to make a ‘spanner’ screwdriver by hacking up a sacrificial flat-head screwdriver. I had my doubts, but with a few days to wait otherwise I decided to give it a shot.

I found a screwdriver that would fit inside the recessed shafts for the screws, and tried to roughly guestimate how far apart the two ‘prongs’ needed to be. The screws were quite small (M3, M2.5? 5/50ths and 1 microfurlong? (I suck at imperial)) and embedded about an inch down a plastic shaft, so it wasn’t really something that I could easily see or measure. Still, I clamped the screwdriver in place and broke out the dremel.

I'm sorry, Mr Screwdriver, but this has to be done.
I’m sorry, Mr Screwdriver, but this has to be done.

Apparently screwdrivers are made out of fairly sturdy stuff – who knew? It took a little while to whittle it down, and my dremel-ing was all over the place. Things were not looking good.

Precision craftsmanship.
Precision craftsmanship.

Still, we’d come this far – time to test it. I inserted the screwdriver into the cutout for the screw – and it got jammed right before it reached the screw. Fantastic! Apparently, when I’d tested if it would fit earlier, I’d confused it contacting the screw with the diameter of the screwdriver slightly increasing enough to get jammed in the hole.

Much more dremelling ensued, and the screwdriver was reduced in diameter slightly. At this point, several days had passed and the shops were about to open anyway – but I would not be deterred!

I tried again, and after turning the screwdriver back and forth a little, I felt it very securely fit into the notches on the head of the screw. Victory! The screw was removed easily, and photographed for all to see.

May its defeat be forever known.
May its shame be forever known.

Several screws followed suit, each swiftly removed by my precisely-modified screwdriver. Eventually, I was able to get the doorbell open.

2015-12-30 22.39.27
Time taken: too much. Doorbell cost: probably $2. I question the worthwhile-ness of this process.

Well, that’s the hard part done – now I just need to figure out how to get my doorbell to send emails, and then put it back together in a way that doesn’t terrify casual onlookers.

But for that, you’ll have to wait for part two!

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