How To Use A Left Handed Drill Bit: The Definitive Extraction Guide

A left-handed drill bit, also known as a reverse-helix drill bit, rotates counterclockwise to remove stubborn, stripped, or broken fasteners while simultaneously driving them out. Achieving success with these specialized tools requires matching your drill motor to reverse gear, applying steady axial pressure, and using a cutting fluid to prevent premature work-hardening of the metal.

Pre-Operation & Equipment Checklist

Successfully extracting a damaged screw, bolt, or stud demands careful planning and specific heavy-duty hardware. Reverse-helix drilling relies on friction and bit bite rather than sheer force, meaning your preparation directly dictates whether the fastener backs out or shears deeper into the material.

• Essential gear, tools, and materials: Cobalt or high-speed steel (HSS) left-handed drill bits (typically sized from 1/8-inch to 1/4-inch), a variable-speed reversible drill motor, center punch, ball-peen hammer, cutting fluid or tapping oil, safety glasses, and a wire brush.
• Mandatory prerequisite knowledge: Understanding that your power drill must be switched into reverse (counterclockwise rotation) and set to a low-to-medium RPM range (typically 400 to 800 RPM) to prevent thermal degradation of the bit tip.
• Estimated budget and duration benchmarks: A standard fractional left-handed drill bit set costs between $25 and $60 USD, while individual extractor bits cost $5 to $15 USD; a typical extraction procedure takes 10 to 20 minutes per fastener.

Step-by-Step Extraction Workflow

Step 1: Clean and Prepare the Damaged Fastener Surface

Clear away all rust, scale, grease, and dirt surrounding the stuck fastener using a wire brush or scraper. Any debris on the fastener head will cause your center punch to wander, leading to an off-center hole that can ruin the surrounding threads or material.

Warning: Never attempt to drill an uncleaned fastener surface, as embedded grit will immediately dull the cutting edges of your left-handed bit.

Step 2: Center Punch the Fastener Head

Place a sharp center punch directly in the exact center of the broken screw or bolt head. Strike the top of the punch firmly with a ball-peen hammer to create a deep, well-defined dimple. This dimple acts as a mechanical guide to prevent the drill bit from walking across the hardened steel surface during initial engagement.

Step 3: Configure the Drill Motor and Lubrication

Insert the appropriately sized left-handed drill bit into your drill chuck and tighten it securely. Switch your drill motor to reverse (counterclockwise rotation) and select a low mechanical gear if your drill has a multi-speed transmission. Apply a generous drop of cutting fluid or tapping oil directly onto the center-punched dimple to reduce friction and lower operational temperatures.

Step 4: Engage the Fastener and Apply Axial Force

Place the tip of the left-handed bit inside the center-punched dimple. Hold the drill perfectly perpendicular to the work surface, apply firm, steady body weight forward, and squeeze the trigger to run the drill in reverse.

Pro-Tip: Maintain a slow, deliberate RPM (around 500 RPM) while applying heavy, constant pressure; rushing the process or spinning the bit too fast will generate excessive heat and blunt the cutting flutes.

Step 5: Monitor for Self-Extraction and Clear Chips

As the left-handed bit digs into the metal, the counterclockwise torque will often grab the walls of the drilled hole and unscrew the entire fastener before you even reach the point of needing a secondary bolt extractor. Periodically back the bit out of the hole, clear away metal chips, and reapply cutting fluid to maintain optimal cutting efficiency until the fastener completely backs out.

Left-Handed Drill Bits vs. Standard Drill Bits and Extractors

Common Extraction Failures and Field Fixes

• Root Cause: The drill bit is spinning clockwise instead of counterclockwise, causing it to bite deeper into the damaged fastener and lock it permanently into the pilot hole.
  
  
  • Actionable Fix: Immediately stop drilling, switch the direction toggle on your power drill to reverse, clean out any packed metal shavings, and restart the extraction process.
• Root Cause: Excessive drill RPM combined with a lack of cutting fluid has caused the steel left-handed bit to overheat, losing its temper and blunting the cutting edges.
  
  
  • Actionable Fix: Grind the tip of the bit flat and resharpen the cutting flutes on a bench grinder at a 118-degree point angle, or replace the damaged bit with a new cobalt variant and apply liberal amounts of cutting fluid.
• Root Cause: The drill wandered off-center during the initial bite, resulting in the bit digging into the surrounding softer parent material (such as aluminum engine blocks) instead of the steel bolt.
  
  
  • Actionable Fix: Stop immediately, fill the ruined hole with high-strength metallic epoxy filler, allow it to fully cure, re-center your center punch with greater precision, and step down to a smaller diameter starter bit.

Frequently Asked Questions

Do left-handed drill bits actually remove broken bolts?

Yes, they are highly effective for removing broken fasteners. Because they rotate counterclockwise, the cutting action imparts a natural unscrewing force on the stuck fastener, meaning the bit frequently catches and spins the bolt completely out while drilling.

What size left-handed drill bit should I use for extraction?

As a general rule of thumb, choose a drill bit that is approximately 50 to 60 percent of the diameter of the broken fastener. For example, use a 1/8-inch bit for a 1/4-inch bolt, ensuring you leave enough wall thickness to grip without damaging the internal threads.

Can I use left-handed drill bits in a standard cordless drill?

Yes, any standard reversible variable-speed cordless drill or corded drill can operate left-handed drill bits. You simply need to ensure the directional switch is set to reverse so the chuck spins counterclockwise.

Will a left-handed drill bit work on hardened steel bolts?

Standard high-speed steel (HSS) left-handed bits will struggle with grade 8 or hardened industrial bolts. For hardened applications, you must use cobalt left-handed drill bits to successfully penetrate the metal.

Master Fastener Extraction Today

Equipping your workshop with a quality set of cobalt left-handed drill bits transforms frustrating stripped-bolt emergencies into routine maintenance tasks. Secure your extraction gear and start spinning out stubborn fasteners with confidence.