Turns out, the ‘normal’ sized SIM card I’ve been using for years is actually the 2nd generation of it’s kind, the first one (or first-form-factor) being a credit card sized version. Not only that, but since I last got a new phone, there’s a 3rd and 4th generation that have been released. And my new phone had space only for the third-form-factor sized SIM or ‘micro’ SIM, which was annoying. I called up T-Mobile, and they agreed to send me a new SIM for free, but it would take three days and my phone would be disconnected while that was happening. Or I could pay a tenner and do it at a T-Mobile shop. Which was more annoying. And unnecessary.
So the great news is, they all seem to have the same chip, and contact arrangement. They’re essentially the same thing, but with more or less plastic attached. So the be all and end all of this instructable is that I got a really nice sharp pair of scissors, and cut carefully around the edges of the chip, using a micro-SIM to normal-SIM adapter as a guideline. And it worked really well.
You can get little plastic stickers which stick onto your normal-SIM as a template, to help out. I had the adapter to hand, so I was able to use it as a test to make sure the contacts remained in the same place. You can see in the pictures.
The only extra note I think I need to add is that my SIM card had extra contacts around the edge of the six standard ones on a micro-SIM. I just cut through them with no ill effects. Although that’s a good reason to make sure your scissors are ‘really nice’ and ‘sharp’. Which I mentioned earlier.