Metallics BHDM7 Bell Hanger Drill Bit Dia 3/8" 18" Carb tip Fish Hole (1pc)

At 18 inches overall the BHDM7 gives you enough length to go through a 2x4 or 2x6 stud bay and out the other side, or to angle down through a top plate and double plate from an attic. For deeper runs you need a longer bell hanger bit or an extension; the 18 inch length is the working figure here.

The fish hole is drilled through the shank near the tip, so once the bit is through the wall you thread your pull string or cable through the hole and back the bit out, dragging the wire with it. That is why electricians and low voltage installers use a bell hanger bit instead of a standard auger: one pass drills and fishes.

It is carbide tipped, which is what lets a bell hanger bit cut masonry, brick, and block in addition to wood and plaster. A high speed steel wood bit will not survive those materials. Run it in hammer-off rotary mode.

Use the bell hanger bit when you need to drill and immediately pull wire through the same hole, which is the usual case for a thermostat, doorbell, camera, or alarm drop through an exterior wall. The 3/8 inch carbide tipped BHDM7 handles the mixed wood-and-masonry path you hit on a through-wall penetration. A flexible auger is the better tool when you need to snake between studs inside a finished cavity rather than straight through.

One bit per order, supplied in a pouch. If you are stocking a van or outfitting a crew for a multi-unit rough-in, order the quantity you need rather than expecting a multi-pack.