Stainless Steel Cup Head Bolts or Coachbolts are commonly called Carriage Bolts. They have a mushroom head and square neck which can be placed inside a recess to aid tightening the nut. Often used to hold framing type timber together, particularly where a decorative finish is required or where the head side is in a heavy foot traffic area to reduce personal injury caused by rubbing past a protruding head i.e. decks, railings and steps.
Most Coachbolts are made to Din 603 standard but in the longer lengths (over 150mm) they are also made with extra thread so they can cover a wider range of clamping thicknesses. They are made out of both grade 304 stainless steel (suitable as a general purpose grade) and 316 stainless steel. Grade 316 is recommended by the Australian Stainless Steel Development Association as a minimum within five kilometres of the surf or moderately corrosive environments.