Metallics BHDM4 Bell Hanger Drill Bit Dia 1/2" 13" Carb tip Fish Hole (1pc)

The BHDM4 is a 1/2 inch diameter bell hanger bit with a 13 inch overall length, so it drills a 1/2 inch hole and reaches through thick sill plates, double top plates, and masonry walls that a standard jobber-length bit cannot clear.

The fish hole is a small eyelet drilled through the shank near the tip. After you bore through the wall or plate, you thread your wire or pull string through the hole and back the bit out, dragging the wire with it, so one pass both drills and fishes. That is why the BHDM4 is the bit electricians and low voltage installers reach for on retrofit wire pulls instead of a plain auger.

It has a carbide tip, so the BHDM4 handles masonry such as brick and block in addition to wood and plaster. The carbide is what lets it survive hitting a nail or mortar joint mid-pull, which is the usual killer of a standard high speed steel bit on a rewire.

One bit per pack, supplied in a pouch. If you are kitting out a crew or standardizing van stock across several techs, order one unit per bit you need rather than expecting a multi-pack.

A 1/2 inch hole, which is what the BHDM4 bores, is the common size for running single NM cable runs, coax, Cat5e/Cat6, or thermostat and alarm wire through a plate or wall. For bundling several NM cables through one penetration you want a larger diameter bit. The 1/2 inch size is the general purpose pick for a single fished run.

For most single wall cavities, a double top plate, or a sill plate the 13 inch length of the BHDM4 reaches on its own. You only need a bit extension when you are drilling at an angle down a long stud bay or stacking through multiple framing members in one shot.