There's a really easy trick for getting the needle off without putting any force on the dial face - it's not completely foolproof, but it does have a significantly higher chance of working the older the gauge is. Having removed the mechanism from the case, you then hold the mechanism in one cupped hand so that you can hold the aluminium disc steady with the fingers of that hand (so you can stop it rotating). The take hold of the centre of the needle with the other hand and try to rotate it while you hold the alumium disc steady - pull gently as you rotate and the needle will come off in your h