SeaKing Stores › 12mm cobalt HSS-CO jobber drill bit - EACH 12mm cobalt HSS-CO jobber drill bit - EACH £23.80 12mm diameter cobalt HSS-CO jobber drill bit. Sold individually, not as the purchase pack. Supplier reference: HSSCO120. Add To Cart Added! 12mm diameter cobalt HSS-CO jobber drill bit. Sold individually, not as the purchase pack. Supplier reference: HSSCO120.