Left Hand Drill Bits: Remove Broken Bolts Easily

By Drill Hog® | Published: 2026-10-17

Category: How-to Guides

Learn how left hand drill bits work to extract broken bolts and screws. Step-by-step removal guide with tips on choosing the right reverse drill bit set.

Quick Answer

Left hand drill bits spin counterclockwise, which can loosen a broken bolt as you drill. Use a left handed drill bit set to extract stuck fasteners without damaging the surrounding material. Start with a small center punch, drill slowly, and let the reverse twist do the work.

Why Left Hand Drill Bits Work for Extraction

Standard right hand drill bits rotate clockwise and tighten a broken fastener as you drill. Left hand drill bits (also called reverse drill bits) rotate counterclockwise, applying torque in the loosening direction. This often frees the bolt before you even need a separate extractor tool. The 135-degree split point on many left hand sets, like those from Drill Hog, helps prevent the bit from walking on the surface, giving you a clean starting hole even on rounded or broken bolt faces.

Choosing the Right Left Handed Drill Bit Set

For most automotive and equipment repairs, a fractional set covering 1/16" to 1/4" or 1/2" gives you the range to match common bolt sizes. Niobium Nb41 steel offers excellent wear resistance and heat tolerance for tough extraction jobs. The Drill Hog 13 Pc Left Hand Niobium Nb41 set covers 1/16" to 1/4" in 1/64th increments, which is ideal for smaller fasteners. If you need larger sizes or want both left and right hand bits in one kit, the 44 Pc set includes both orientations from 1/16" to 1/2" in M7 high-molybdenum steel.

How to Remove a Broken Bolt with Left Hand Drill Bits

1. Center Punch the Broken Bolt: Use a center punch to create a small dimple exactly in the center of the broken bolt face. This prevents the drill bit from walking off the hard surface. Checkpoint: If the bolt face is uneven, file it flat before punching. A wandering bit can damage the threads in the hole.
2. Start with a Small Left Hand Bit: Select a left hand bit about half the diameter of the bolt. Apply steady, light pressure at a low drill speed (300–500 RPM). Let the reverse twist bite into the metal. Common mistake: Using too much speed or force can snap the bit. Go slow and let the bit cut, not push.
3. Gradually Increase Bit Size: Step up to larger left hand bits in the set, drilling deeper each time. The counterclockwise rotation often catches the bolt and spins it out before you reach full depth. Checkpoint: If the bolt starts turning with the bit, stop drilling and use pliers or a wrench to finish removing it by hand.
4. Switch to an Extractor (If Needed): If the left hand bit drills through without loosening the bolt, insert a screw extractor into the pilot hole. Tap it in gently, then turn counterclockwise with a tap wrench. Verdict: Left hand bits succeed about 70% of the time on their own. An extractor is a backup, not the first move.

Recommended Left Hand Drill Bit Sets

13 Pc Left Hand Drill Bit Set Niobium Nb41 Drill Hog®: 13 fractional sizes from 1/16" to 1/4" by 1/64ths, made of Niobium Nb41 steel with a 135-degree split point. Covers the most common small bolt and screw sizes found in automotive and machinery. The split point reduces walking, and the Nb41 steel holds up under the high torque of extraction.
44 Pc Left Hand Drill Bit Set Left Hand Drills Reverse Twist Moly M7 Drill Hog®: 44 piece set with 29 right hand and 15 left hand fractional bits from 1/16" to 1/2" in M7 high-molybdenum steel. Gives you both orientations in one case, so you can drill a pilot hole with a right hand bit and switch to a left hand bit for extraction. M7 steel offers good heat resistance for repeated use.