U.S. Pat.  No.  3,880,546 discloses a prior art hole saw assembly which includes a hole saw and an arbor assembly.  The hole saw includes a ramp having a slot therein which is used to lock the hole saw to the arbor assembly.  The arbor assembly includes a pin extending from a pin sleeve, which has a shank extending from the pin sleeve and an enlarged head at the free end thereof.  The enlarged head passes through an enlarged portion of the slot in the hole saw and engages behind the ramp.  To maintain the hole saw on the arbor assembly, the operator twists the hole saw and the arbor assembly in opposite directions, the enlarged head travels along the ramp, until the pin sleeve is secured to the hole saw.