How to Use Left Handed Drill Bits Easily - Daily Hand Tools: Your Everyday Guide

Can you use left-handed drill bits in a standard drill? Yes, you can absolutely use left-handed drill bits in a standard drill. The key is to set your drill to rotate in the reverse direction. Left-handed drill bits, also known as reverse drill bits, are specifically designed to cut while the drill spins counter-clockwise. This unique design makes them incredibly useful for a variety of tasks, especially for removing broken screws and drilling stubborn screws. This guide will walk you through how to use left handed drill bits easily, covering everything from choosing the right bit to mastering the left hand drill technique.

How To Use Left Handed Drill Bits
Image Source: m.media-amazon.com

Why Choose Left Handed Drill Bits?

Standard drill bits are designed to cut as the drill spins clockwise. This is the most common direction for drilling. However, there are situations where this standard operation can be problematic, and this is where left handed drilling shines.

Left hand drill application is particularly beneficial in these scenarios:

Removing Stuck or Broken Fasteners: When a screw head is stripped or the screw itself has broken off within a material, a standard drill bit can often make the problem worse by further embedding the fastener or damaging the surrounding material. Drilling with left hand bits can sometimes back out the broken piece as you drill into it.
Preventing Material Breakthrough: In delicate materials, drilling in the standard direction can exert outward pressure, potentially causing the material to split or break apart as the bit exits. Left handed drilling can sometimes create a less aggressive cutting action, reducing this risk.
Lubrication and Cooling: The reverse rotation can sometimes help draw cutting fluid or lubricant towards the cutting edge, improving bit life and cutting efficiency, especially in harder materials.

Deciphering the Design of Left Handed Drill Bits

The fundamental difference between standard (right-handed) drill bits and left-handed drill bits lies in the angle of their flutes.

Standard Drill Bits: Have flutes that spiral to the right. As they spin clockwise, the angled edges of the flutes cut into the material and eject chips upwards and out of the hole.
Left Handed Drill Bits: Have flutes that spiral to the left. When a drill is set to rotate counter-clockwise, these flutes engage the material and, crucially, can exert a leftward force. This is the core of why they are effective for removing broken screws. The counter-clockwise rotation, combined with the leftward cutting action, can help to unscrew the broken piece.

Key Features of Left Handed Bits:

Left-Handed Spiral Flutes: This is the defining characteristic.
Sharper Cutting Edges: Often manufactured with a sharper cutting edge to bite into material more effectively.
Durable Materials: Typically made from high-speed steel (HSS) or cobalt alloys for strength and heat resistance.

Selecting the Best Left Handed Bits

When it comes to best left handed bits, quality matters. Not all left-handed bits are created equal, and investing in good quality bits will save you frustration and time.

Types of Left Handed Drill Bits:

Solid Left Handed Bits: These are solid pieces of metal with the left-handed spiral. They are very durable and are excellent for general drilling and for use with broken fasteners.
Left Handed Step Bits: These are multi-sized bits that are useful for drilling holes of various diameters in thinner materials like sheet metal. They can also be effective for gradually enlarging holes and are sometimes used in the process of removing broken screws when the screw is not completely seized.

What to Look For:

Material: High-speed steel (HSS) is a good standard. For harder materials or more demanding applications, consider cobalt-infused HSS or solid cobalt bits.
Web Thickness: A thicker web (the central part of the bit) provides more strength and rigidity, reducing the chance of the bit bending or breaking.
Point Grind: Different point grinds are suited for different materials. A standard 118-degree point is good for general use, while a 135-degree split point is better for harder metals and reduces the tendency for the bit to “walk” across the surface.
Flute Design: While all left-handed bits have left-handed spirals, some may have deeper or more aggressive flute designs for better chip evacuation.

Setting Up Your Drill for Left Handed Drilling

This is a crucial step for drilling with left hand bits. If your drill is set to rotate clockwise, your left-handed bit will not cut effectively; it will essentially be pushing material away rather than cutting it.

Adjusting Drill Rotation:

Most modern cordless drills and corded drills have a directional switch. This switch controls whether the drill chuck spins clockwise (forward) or counter-clockwise (reverse).

Locate the Directional Switch: This is typically a toggle switch located near the trigger of your drill. It often has an arrow indicating forward and another indicating reverse, or symbols like “F” and “R”.
Set to Reverse: To use left-handed drill bits, you must set this switch to the reverse position. You want the drill to spin counter-clockwise.
Test the Rotation: Before inserting a bit, point the drill in a safe direction (away from yourself or others) and squeeze the trigger. Observe the direction the chuck spins. It should be spinning counter-clockwise.

Speed Settings:

When drilling with left hand bits, especially for removing broken screws, you’ll generally want to use a slower speed setting.

Lower Speeds: Provide more torque, which is essential for biting into stubborn materials and for controlling the process of backing out a broken fastener.
Higher Speeds: Can lead to overheating of the bit and material, and can make it harder to control the drill, increasing the risk of further damage.

Most drills have a speed selector, often a collar near the chuck or a numbered dial. Aim for the lower speed settings.

The Left Hand Drill Technique: Step-by-Step

Mastering the left hand drill technique is key to successful left handed drilling. It’s about patience and control.

Step 1: Prepare the Workpiece and Safety Gear

Secure the Material: Ensure the material you are drilling is firmly clamped or held in place.
Safety First: Always wear safety glasses or goggles. If working with materials that create dust, wear a dust mask. Gloves can provide a better grip.

Step 2: Center Punching (If Necessary)

For precise drilling, especially when attempting to extract a broken screw, it’s good practice to create a small indentation at the exact spot where you want to drill. This prevents the drill bit from “walking” across the surface.

Use a center punch and a hammer to create a small divot.

Step 3: Selecting the Right Size Left Handed Bit

The size of the reverse drill bits you choose depends on the task.

For Removing Broken Screws: You typically want to start with a bit that is smaller than the shank of the broken screw. The goal is to drill into the screw itself. As you drill counter-clockwise, the bit’s action might help to grip and unscrew the broken piece. If the screw is particularly large, you might need to progressively use larger left-handed bits.
For General Drilling: Choose a size appropriate for the hole you need to create.

Step 4: Initiating the Drill (The Crucial Part)

This is where the left hand drill technique comes into play.

Set Drill to Reverse: Ensure your drill is set to rotate counter-clockwise.
Apply Steady Pressure: Place the tip of the left-handed drill bit on your mark or center punch.
Start Slowly: Gently squeeze the trigger to start the drill at a very low speed.
Listen and Feel: Pay close attention to the sound and feel of the drill. You should feel the bit begin to bite into the material.
Increase Pressure Gradually: As the bit starts to cut, gradually increase the pressure. Avoid forcing the drill; let the bit do the work.

Step 5: Drilling Through the Material

Maintain Speed and Pressure: Continue drilling with steady pressure.
Chip Evacuation: Keep an eye on the flutes of the bit. If they become clogged with debris, stop drilling, set the drill to forward briefly to clear the chips, then switch back to reverse and continue. Or, if possible, pull the bit out while it’s still spinning in reverse to help clear the hole.
Lubrication: For harder materials, consider using a cutting fluid or lubricant to keep the bit cool and improve its lifespan. Apply it directly to the tip of the bit or the work area.

Step 5.5: The Art of Removing Broken Screws

This is a primary application for left handed drilling.

Center Punch: Accurately center punch the broken screw.
Choose a Small Bit: Select a left-handed bit that is smaller than the diameter of the broken screw shank.
Drill into the Screw: Set your drill to reverse and drill into the center of the broken screw.
Listen for the “Unscrewing” Action: As you drill, the counter-clockwise rotation and the leftward spiral of the bit may catch the screw and begin to unscrew it. You might hear a slight change in sound or feel the drill back itself out.
Increase Bit Size if Needed: If the initial bit doesn’t work, you may need to step up to a slightly larger left-handed bit, continuing to drill into the center of the screw. The goal is to create a hole deep enough for the bit to catch the threads or body of the screw.
Impact Driver (Caution): In some cases, if the screw starts to loosen but remains stubborn, a brief burst from an impact driver (set to reverse) might help, but use extreme caution as this can also break the screw further or damage the material.

Step 6: Completing the Hole or Extraction

Exiting the Material: As you approach the exit point of the hole, reduce pressure slightly to prevent blow-out on the other side, especially in softer materials.
Removing the Bit: Once the hole is complete, or the broken screw has been extracted, switch the drill to forward briefly to help clear any remaining debris from the bit. Then, pull the bit out while the drill is stopped.

Troubleshooting Common Issues

Even with the right tools and technique, you might encounter challenges.

Issue: Bit Not Cutting

Cause: Drill set to forward (clockwise) instead of reverse.
Solution: Double-check your drill’s directional switch. Ensure it’s firmly set to reverse.
Cause: Insufficient pressure.
Solution: Apply more steady, firm pressure to the drill. Let the bit bite.
Cause: Dull or poor-quality bit.
Solution: Try a different, sharper left-handed bit. Consider investing in higher-quality bits.
Cause: Material is extremely hard.
Solution: Use a cutting fluid and a slower drill speed. Consider a cobalt bit.

Issue: Broken Screw Not Backing Out

Cause: Screw is seized or rusted into the material.
Solution:
- Try a slightly larger left-handed bit.
- Apply penetrating oil to the screw and let it soak.
- Carefully tap the end of the screw with a hammer and punch to help break any rust bond.
- If you have an impact driver, try very short, controlled bursts in reverse.
- Consider a screw extractor kit designed specifically for broken screws as a next step. These often involve drilling a pilot hole and then using a reverse-threaded extractor.

Issue: Bit Wandering When Starting

Cause: No pilot hole or center punch.
Solution: Always use a center punch for precise starting points, especially on smooth surfaces or when drilling into existing fasteners.

Issue: Bit Overheating

Cause: Drilling too fast or without lubrication.
Solution: Reduce drill speed. Use cutting fluid, especially on metal. Drill in short bursts, allowing the bit and material to cool.

Left Hand Drill Application: Beyond Broken Screws

While removing broken screws is a prime application, drilling with left hand bits has other uses:

Tapping Holes: When you need to tap a hole for threads, drilling the pilot hole in reverse can sometimes lead to a cleaner hole that is easier to tap.
Drilling Plastics: In some plastics, the outward pressure of a standard drill bit can cause the plastic to melt or crack. Left handed drilling can sometimes create a cleaner hole with less stress.
Working with Specific Metals: Certain metals can be more difficult to drill. The cooling and chip evacuation properties of left handed drilling can be advantageous.

When Not to Use Left Handed Drill Bits

While versatile, left-handed bits aren’t always the best choice.

When You Need to Create Threads: If you are drilling a pilot hole for tapping threads, you generally want the hole to be precise for the tap to cut correctly. While left handed drilling might be used in preparation, the final drilling for tapping is usually done with a standard bit in the forward direction.
When Drilling into Fragile Materials (Without Care): While they can sometimes reduce blowout, if not used carefully with appropriate speed and pressure, they can still damage delicate materials.
When the Goal is to Secure a Fastener: If you are simply drilling a hole to drive a new screw or bolt, a standard drill bit in the forward direction is what you need.

Comparing Left Handed Bits to Screw Extractors

It’s important to distinguish between left-handed drill bits and screw extractors. Both are used for removing stubborn fasteners, but they function differently.

Feature	Left Handed Drill Bits	Screw Extractors
Primary Function	Drilling (cuts material)	Gripping and unscrewing (threads into material)
How they Work	Cut into material as drill spins counter-clockwise. May help unscrew if the screw is not too tight.	Have reverse threads that bite into a drilled hole in the fastener.
Application	Removing broken screws, drilling in reverse, general drilling.	Primarily for removing broken/stripped screws.
Requirement	Drill set to reverse rotation.	Drill set to reverse rotation (for drilling pilot hole and for extractor to grip).
Design	Left-handed spiral flutes.	Tapered with reverse threads.

Left-handed drill bits are often the first tool you might reach for when dealing with a broken screw. If the screw starts to loosen but remains stuck, you might then move on to a dedicated screw extractor.

Maintaining Your Left Handed Drill Bits

Proper care will ensure your best left handed bits last a long time.

Clean After Use: Remove any debris from the flutes with a brush or compressed air.
Lubricate: Apply a light oil to prevent rust, especially if storing them for extended periods.
Store Properly: Keep them in a bit case or organizer to prevent them from rolling around and becoming damaged.
Sharpening: If you are experienced with sharpening drill bits, left-handed bits can be sharpened. However, it’s a specialized process to maintain the correct spiral and cutting angles. For most DIY users, replacing a dull bit is often more practical.

Frequently Asked Questions (FAQ)

Q1: Can I use left-handed drill bits for regular drilling?
A1: Yes, you can use left-handed drill bits for general drilling. However, you must ensure your drill is set to rotate in the counter-clockwise (reverse) direction. If you set the drill to clockwise (forward), the bit will not cut effectively.

Q2: What is the main advantage of using reverse drill bits?
A2: The primary advantage of reverse drill bits (left-handed drill bits) is their effectiveness in removing stubborn or broken screws. The counter-clockwise rotation combined with the left-handed spiral can often grip and back out a broken fastener as you drill.

Q3: How do I know if my drill is set to reverse?
A3: Most drills have a directional switch located near the trigger. Look for arrows or symbols indicating forward (clockwise) and reverse (counter-clockwise) rotation. Ensure the switch is in the “reverse” position. You can test it by pointing the drill safely and squeezing the trigger.

Q4: Can left-handed drill bits help with stripped screws?
A4: Yes, left handed drilling can sometimes help with stripped screws, especially if the screw head is still somewhat intact. By drilling in reverse, the bit might catch an edge of the stripped head or even the shaft, allowing it to be backed out. However, for severely stripped screws, other methods like screw extractors or specialized pliers might be more effective.

Q5: What’s the difference between left-handed drill bits and screw extractors?
A5: Left-handed drill bits are designed to cut material while spinning counter-clockwise, and this action can sometimes unscrew fasteners. Screw extractors are specifically designed with reverse threads that bite into a pre-drilled hole within a broken fastener to unscrew it. They are different tools with related but distinct functions.

Q6: Are there specific types of materials where left-handed bits are better?
A6: While they can be used on many materials, left handed drilling is often advantageous when drilling stubborn screws, removing broken fasteners, or in certain situations with metals or plastics where outward pressure from standard drilling can cause damage. They can also offer a slight advantage in chip evacuation and cooling when used with cutting fluids.

By following these guidelines, you can effectively utilize the unique capabilities of left-handed drill bits, making tasks like removing broken screws significantly easier and more successful. Remember to prioritize safety and select the right bit for the job.