so we'll start from the start, and you'll need some tools. i bought a halfords multitool(like a dremel) and didnt use it, despite the site i took inspiration from saying it was a must. instead i used a large metal file, hammer, 1.5mm drillbit, pliers and a vice. i'd recommend a set of needle files to get it looking better and you will have more control than a large file...oh, and a flip key (got mine off ebay, £10 all in)
first off, removing the old blade from the flip key. open the blade half way and you will see a small roll pin, knock it out using the drill bit and hammer (dont lose it) and remove the blade. it may take some persuasion. you should be left with this...
next you need to remove the plastic bit from your spare. i found a blowtorch works quite well, and doesnt take too much time... anyway, after a bit of cleaning and filing off the tabs on the key, you should have this...
note you "spare" blade is longer, so needs trimming down, to this..
then you need to file one side of the key flat to get the "height" right.
if you sit the original blade on your's, you should be able to get a good idea of length, and you will notice that your blade is slightly wider, but it does fit in the fob. so you need to file the edges slightly to make it slimmer. dont go too crazy, as the key will end up rattling around. once you are at this stage, you should start to trial fit the key in the fob and trimming as appropriate. once you are happy, make sure the key opens and closes nice and free in the fob, reshape if needed.
next, you need to file in the notch for the roll pin to sit. do this on the opposite side to where you flatted the key. measure against the old blade, but so long as you dont file too far back you should be alright. once the hole is cleared and the pin can be refitted (i placed it in, then used the vice to slowley press it through) your key should be ready!
this was done using a cavalier (1994) key, but i'm guessing the same principal could be applied to early vectra, corsa, nova, astra, so long as the width of the key fits within the fob
some things to look out for...
dont file your key too short, if you do it wont fit the ignition properly, as it sits close enough as it is.
if you mess up after reading this, please note that i take no responsibility, as common sense should prevail.
