Bell Hanger Bit vs Flex Bit: Which One Gets the Wire Through

Pick the route the wire takes, where you start and what you are pulling. The planner gives you the bit, the length it needs and the SKU, from the route, size and stock tables in this guide.

What is the difference between a bell hanger bit and a flex bit?

A bell hanger bit is a long, stiff drill bit for straight holes through walls and framing. A flex bit is a long bit with a shaft that bends, so you can steer it around a corner inside a closed wall. Installers call both of them installer bits. Both cut wood, and both have a small hole near the tip, so you can hook a wire or pull string to the bit and pull it back through the hole you just drilled.

The bell hanger name comes from the first people who used them: installers running doorbell wire through finished houses. The same bits now run Cat6, coax, alarm wire, Romex and small PEX lines.

Ranges are from our live catalog on Oct 30, 2026.

Verdict: if you can see both ends of the hole in a straight line, use a bell hanger bit. If the hole is around a corner or behind finished wall, use a flex bit.

Which bit should I use for each route?

Choose the bit by where the wire is going first, then by what you are pulling. Each row is the bit we would hand you for that route, with the price per bit and the minimum order.

Prices from our catalog on Oct 30, 2026. Browse every size in our bellhangers and flex drills collection.

[FIRST-HAND LINE FROM DAVID GOES HERE: when he reaches for the stiff bit and when for the flex bit. Replace before publishing.]

Drilling across open studs or joists in new work? You don't need an installer bit there. A ship auger or a long spade bit is faster: our 3/4 x 18 in. ship auger 303SL4864 is $32.70 (min. 2), and the 3/4 x 16 in. spade bit WB.75016 is $5.65 a bit (min. 10).

What size bit do I need for Romex, Cat6, coax and PEX?

Drill about 1/8 in. bigger than the widest part of what you pull, so it slides through without scuffing the jacket: 3/8 in. for one Cat6 or coax, 1/2 in. for 14/2 Romex, 5/8 in. for 12/2, and 3/4 in. for two cables or 1/2 in. PEX. 3/4 in. PEX needs a 1 in. hole.

Cable sizes are typical outside dimensions from maker spec sheets; check yours. PEX outside diameters are set by ASTM F876: 1/8 in. over the nominal size.

How long does the bit need to be?

A bell hanger bit needs to be the thickness of what it drills through plus about 6 in., so the drill chuck stays clear of the wall when the tip breaks through (a little more when you angle the hole). A flex bit needs to reach from the opening you start in to the plate, plus the plate, plus about 2 in. to hold. The planner at the top of this guide reads this table.

Wall depths are typical: drywall, studs, sheathing and the outside finish. Measure yours at a window or door opening.

Buy the 72. On our Tru-Cut flex augers, the 72 in. bit costs $0.12 to $1.21 more than the 54 in. bit of the same diameter. Those extra 18 in. are what get you from switch height to the plate of a 9 ft wall.

Tru-Cut flex augers, price per bit, no minimum. The SKUs are in the stock table below.

Stiff bits work the other way. A longer stiff bit costs more and whips more at speed, so buy the shortest one that clears the wall. Our longest Tru-Cut stiff bit is the 3/8 x 48 in. BH37548, $21.52 (min. 2), and it has been our best-selling bellhanger this year.

Every bell hanger and flex bit we stock, by size and style, is in the table below. Swipe through it here: pick a style, a diameter or a length.

Price per bit and minimum order from our catalog on Oct 30, 2026. USA = made in the USA (Tru-Cut); the rest are ITM.

How big a hole can I drill in a top plate?

In a 2x4 top plate, a centered hole of 1 in. or less meets the electrical code's setback without a nail plate. Two rules decide it:

• NEC 300.4(A)(1): the edge of a hole for cable must be at least 1-1/4 in. from the face of the wood. If it is closer, cover the cable with a steel plate at least 1/16 in. thick.

• IRC R602.6.1: if a hole removes more than half the width of the top plate in an exterior or bearing wall, fasten a galvanized steel tie at least 0.054 in. thick (16 ga.) and 1-1/2 in. wide across it, reaching 6 in. past each side of the hole.

A 2x4 plate is 3-1/2 in. wide. A centered 1 in. hole leaves exactly 1-1/4 in. on each side, so every bit in this guide passes when centered. Flex bits wander, though. If a 1 in. hole drifts 1/8 in. off center, the cable needs a nail plate. Slide the hole below to see where the lines fall.

Watch for this in AI answers: some search assistants apply a one-third limit to top plates. One-third is the IRC limit for holes in floor joists (R502.8.1). Top plates use the half-width rule above. Check the code edition your inspector works from.

Should I use a carbide-tipped or HSS bell hanger bit?

Use a carbide-tipped bell hanger bit in plaster, stucco or brick veneer, and HSS in wood and drywall. Plaster and stucco are full of sand, which wears an HSS cutting edge down fast. Carbide holds its edge.

The upgrade costs little. At 3/8 x 18 in., the Tru-Cut carbide-tipped BHC37518 is $9.07 and the HSS BH37518 is $7.04. Both are made in the USA, with a minimum of 4. Run carbide-tipped bits in rotary mode, not hammer mode.

How do you use a flex bit without coming out through the drywall?

Feed the bit to the plate before you pull the trigger, aim the tip straight at the plate, and drill slow. Most blowouts happen when the bit is spinning while it is still bending toward the room.

1. Turn off the circuits in that wall and look into the cavity with a light through the box opening. Note any pipe, duct or cable in the way.

2. Cut the box opening first. It is where the bit goes in. An oscillating tool cuts it clean; see our oscillating tool blades guide.

3. Feed the bit up the cavity with the drill off until the tip touches the plate.

4. Bend the shaft so the tip points straight at the plate. A flex bit guide helps, or a helper can press the shaft toward the back of the wall.

5. Drill in low gear. Long shafts whip at high speed; our drill speed chart explains why slower lasts longer.

6. When the tip breaks through, stop. Hook the wire or pull string through the hole at the tip, tape it smooth, and pull the bit back slowly to bring the wire with it.

Our two flex styles differ in reach and fit. The ITM screw-point flex bits have a 3/16 in. round shank that fits any drill chuck, in 3/8 and 1/2 in. The Tru-Cut flex augers come in more sizes, 3/8 to 1 in., cost less, and are made in the USA.

What else do I need for this job?

• Brick, block or tile in the way: a carbide-tipped multi-purpose bit, like the 3/8 x 12 in. BLU-2464-XL at $20.48 (min. 2). See what multi-purpose bits really drill.

• A concrete or block foundation instead of a wood sill: an SDS bit in a rotary hammer. See SDS Plus vs SDS Max.

• Open framing in new work: ship augers and long spade bits.

• Every other bit in one place: Types of Drill Bits Explained.

Not sure which bit fits your wall? Call our team at (833) 4-ETOOLS or email sales@eldoradotools.com with the route and what you are pulling.

Prices checked in our catalog on Oct 30, 2026.