Starrett's holesaws are excellent products, they cut through timber with no trouble and, with a little patience, make light work of mild steel and aluminium. I have had a little trouble with the arbour drill bits not being quite central which can throw the holesaws off centre.
PACK OF 10 x M12 A2 STAINLESS STEEL DOME NUTS COARSE THREAD DIN1587 ACORN *