Monday, 22 October 2012

Making a security screw driver

I've an old Maplin AA battery charger that although it works well has been dropped a few times and the case got damaged. I don't really want to use it in that state so I thought I'd take it apart and fix the broken components.

My first issue was that it was held in place by 3 unusual screws. A little bit of research into screw heads showed me that this was a "spanner" type head also known as "snake-eyes" or "notched". So I bought myself a little set of security bits with these in and brought it home. I then realised that two of the screws were down the end of some deep and thin holes so my bits were useless as they were too wide to fit.



However, now that I had a bit to copy from and low probabilty of finding the appropriate tool very easily I thought I'd try and build my self a driver with this head.

I tool a piece of hex bar and ground the end into a screwdriver blade. I then carefull filed the gap in the middle to match the selected bit.

I looked up tempering temperature and it recommended a blue colour for screwdriver bits so I heated the bar with a butane torch till it got to a cherry red and then quenched it in some water. I then heated it again with the flame aimed below the tip. I did not see the colour blue get to the tip but I stopped before the orange got there and quenched again. This was my first attempt a tempering since I left the Dowty apprentice workshop so I'll have to practice a bit more.



This just left the handle to make. I was going to do a simple Sugru handle and they provided me some tips on making mini screwdrivers and texturing techniques.

However, I was luckly that a can opener was being decomissioned this weekend so I grabbed the handle from that. After stripping off the excess components I was left with a simple plastic handle. I heated the end of my screw driver and pushed the handle onto it to melt a lovely hexagon shaped hole.



Finally, I used some white Sugru to hold the handle in place.



Those pesky screws.



Having opened up the charger, I believe it can be fixed but that will have to wait till another weekend. I also found online another security bit project.

4 comments:

david whittle said...

awesome article i might have to customize my Ryobi Tools

Andy from Workshopshed said...

Sugru would be an ideal thing to use if you want to put extra grips or cable supports onto your powertools

Alaric Snell-Pym said...

Hey, you worked for Dowty? My grandfather was their "chief technologist" or some such job title back in the day!

I tend to collect the little single-use screwdrivers stamped out of metal plates and similar that come with self-assembly furniture and things like that, then attack them with the grinder whenever I find myself in your situation! I treat the result as a disposable one-off, though, so have never bothered hardening and tempering or making a decent handle!

Andy from Workshopshed said...

I was only there for 3 years on and off as an apprentice but it was a great company to work for. We parted ways when I left college as they were looking for high flying types and I did not fit the profile.

I've quite a few of those double ended hex keys, I did think about turning one into a flathead just the other day but just used a normal screwdriver. In this case the main reason for heat treatment was that the pins were quite small. As mentioned in the next post, the T-bar handle actually caused me trouble as I managed to overtighten the screws and break the plastic case. Retrospectively I'd go for a more contentional handle.

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