A wire tensioner is provided for a wire bonder, the wire tensioner comprising a tubular body having a bore through which bonding wire is receivable and a bore outlet at an end of the tubular body from which the bonding wire is extendable towards a bonding tool. A chamber is formed next to the bore outlet that substantially encloses the bore outlet, the chamber including an air inlet connected to it that is operative to introduce clean air into the chamber. A vacuum outlet is connected to a side of the tubular body and is in fluid communication with the chamber via the bore, the vacuum outlet being operative to draw air from the bore outlet through the bore whereby to pull the wire.