By the way - just curious - You mentionned the shaft on router bit is 1/2". BUT... how about the collett - Is it 1/2" or did you force it in a 12mm? The difference makes 0,5 mm and thats much in these termes. Because I have never ever experienced a bit to get stuck in a collet. But if you did force it in a 12mm, and thats the reason its so stuck, I'd rather discard that collett and replace it with a new one. You cant afford your health if the collet is damaged oand the bit spins out at high speed.
You live in England, MTMC.co.uk has tons of spare parts for Bosch. Colletts are not expensive. Good luck
