5/16 x 24 Ship Auger Bit

This 5/16 x 24 ship auger bit (5/16 in. x 24 in.) drills the long, clean holes that cabling and bracing hardware needs. The single-flute design clears chips well in green wood, so the bit keeps cutting through thick limbs and stems.

Why arborists use ship augers

Installing eye bolts, threaded rod and other through hardware means drilling straight, clean holes through living wood, often more than a foot deep. A ship auger has a single open flute and a lead screw that pulls the bit into the cut. It clears chips well in wet green wood where twist bits clog and bind.

This long 5/16 in. bit reaches deep for small-diameter holes, such as pilot holes. ANSI A300 Part 3 sets out how holes should be sized relative to the hardware, and in general the hole should be only slightly larger than through hardware so it fits snugly. Check the standard and the hardware maker's instructions for the exact size.

A long bit like this lets you drill deep without an extension, but it is easier to bend if the drill is levered sideways. Keep the drill in line with the hole, let the lead screw pull the bit in, and store it in a sleeve or tube so it stays straight between jobs.

Drilling from a climbing position

Drilling aloft puts a lot of torque on you and the drill. Use a drill with a side handle and clutch if you have one, secure your position with two points of attachment where required, and keep your lanyard and climbing line clear of the bit. Back the bit out often to clear chips, and keep the bit sharp so it does not stall. Cabling and bracing is structural work on a living tree. It should be specified and installed by a trained arborist following ANSI A300 Part 3, ANSI Z133 and the hardware maker's instructions, and inspected on a regular schedule after install. Shop hardware and tools in our cabling and bracing section.