Can you use a left-hand drill bit as a regular drill bit? Yes, you can, but it’s not ideal and won’t perform as effectively as a standard right-hand drill bit for general drilling. Left-hand drill bits, often called reverse drill bits, are specifically designed for a different purpose. This guide will delve deep into their unique capabilities, how to use them correctly, and when they become indispensable tools in your workshop.
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What are Left Hand Drill Bits and Why Use Them?
Left-hand drill bits are cutting tools designed to rotate in the opposite direction of standard drill bits – counterclockwise. This unique characteristic makes them incredibly valuable for specific, often challenging, tasks.
The Counterclockwise Advantage
Standard drill bits spin clockwise. When you encounter a stubborn fastener that won’t budge, or a broken bolt lodged in a workpiece, forcing a standard drill bit can sometimes make the problem worse. This is where the counterclockwise drill bit shines. By spinning in the opposite direction, it can achieve what a standard bit cannot.
Key Applications for Left Hand Drill Bits
- Removing Broken Bolts and Screws: This is the most common and critical application. When a bolt or screw head snaps off, leaving the threaded shaft embedded, a left-hand drill bit can often extract it.
- Unscrewing Stripped Fasteners: If a screw head is so damaged that a screwdriver can’t grip it, a left-hand drill bit can sometimes bite into the remaining metal and back it out.
- Clearing Obstructions: In some specific machining or drilling scenarios, the reverse rotation can help clear chips or debris that a forward-rotating bit might push deeper.
- Tapping Operations: While not their primary function, some specialized tapping drill bits are designed for left-hand threads, which are used in specific engineering applications.
How to Use a Left Hand Drill Bit: A Step-by-Step Approach
Using a left-hand drill bit requires a slight shift in your drilling approach. The fundamental principles of drilling remain, but the direction of rotation is key.
Setting Up Your Drill
- Identify the Correct Drill Setting: Most modern drills have a forward/reverse selector switch. Ensure your drill is set to reverse (often indicated by an arrow pointing counterclockwise).
- Select the Right Drill Bit: Choose a left spiral drill bit that is slightly smaller than the diameter of the broken bolt or screw you need to remove. A bit that’s too large can damage the surrounding material. For broken bolts, specialized sets of left handed drill bits for removing broken bolts are available.
- Secure the Workpiece: Clamp your workpiece firmly to prevent it from moving. This is crucial for safety and accuracy.
- Center Punch: For broken bolts, use a center punch to create a small indentation at the exact center of the broken shaft. This will guide the drill bit and prevent it from wandering.
The Drilling Process: Counterclockwise Drilling
Drilling with reverse bit requires patience and a gentle touch.
- Start Slow: Begin drilling at a slow speed. You want the bit to bite into the metal, not to spin out of control.
- Apply Steady Pressure: Apply consistent, downward pressure. As the counterclockwise drill bit begins to cut, it should start to back out the embedded material.
- Observe the Rotation: Pay close attention to the drill’s rotation. You are essentially how to drill backwards compared to your normal routine.
- Chip Evacuation: Keep the hole clear of metal shavings. You might need to periodically withdraw the bit to clear debris.
- When to Stop: Continue drilling until you feel the bit starting to grip the bolt. If the bolt begins to spin out on its own, great! If not, you might need to increase pressure slightly or use an extractor tool.
Using Left-Hand Drill Bits for Broken Bolts
When dealing with broken bolts, the left hand drill bit drilling process is as follows:
- Choose the Right Size: Select a left-hand drill bit that is designed to work with the size of the broken bolt. Often, a set will include multiple sizes.
- Center the Bit: Accurate centering is paramount. A wandering bit can enlarge the hole in the workpiece, compromising its integrity.
- Drill into the Bolt: Slowly drill into the center of the broken bolt. The counterclockwise rotation should, ideally, catch the bolt and unscrew it from its housing.
- Extraction: If the bolt starts to turn, continue drilling with reverse bit to back it out completely. If it doesn’t turn, you might need to use a screw extractor (also known as an easy-out). These extractors are designed to be used with a reverse drill setting.
When Standard Drill Bits Won’t Cut It: The Power of Left-Handed Drill Bits
Standard drill bits are designed for clockwise rotation. This rotation creates a wedging action that helps push material away from the cutting edge. However, in certain situations, this can work against you.
The Challenge of Stubborn Fasteners
Imagine a bolt that’s rusted, cross-threaded, or simply seized within its housing. When you try to loosen it with a standard wrench or screwdriver, you might find it won’t budge. Attempting to drill it out with a standard bit, spinning clockwise, can:
- Further Wedge the Bolt: The clockwise rotation can actually drive the broken piece deeper into the material.
- Worsen the Damage: It can expand the broken bolt, making it even harder to remove.
- Break the Drill Bit: If the bolt is particularly stubborn, the force required could break a standard drill bit.
The Left-Handed Solution
This is where using left drill bits becomes essential. By spinning counterclockwise:
- Unscrewing Action: The cutting action inherently tries to unscrew whatever it’s drilling into. If the broken bolt is still partially engaged, the left spiral drill bits can grab it and unscrew it.
- Reduced Wedging: The counterclockwise motion is less likely to wedge the broken material further.
Common Scenarios for Using Left-Hand Drill Bits
Removing Broken Studs and Bolts
This is the bread and butter of left handed drill bits for removing broken bolts. Often, the head of a bolt or stud snaps off during removal.
- Assess the Situation: Determine how much of the bolt shank is protruding. If it’s flush or recessed, drilling is usually required.
- Center Punch: Precisely mark the center of the broken bolt.
- Drill Selectively: Start with a small left hand twist drill bits and gradually move to larger ones if needed. The goal is to drill into the bolt itself.
- Extractor Use: If the bolt doesn’t back out on its own, insert a screw extractor into the drilled hole. These tools have reverse threads that grip the inside of the hole as you turn them counterclockwise.
Dealing with Stripped Screw Heads
When a screw head is stripped, the drive slot (Phillips, flathead, Torx) is damaged, preventing a screwdriver from gaining purchase.
- Find a Grip: Sometimes, a left-hand drill bit can be used to bite into the outer edge of the stripped screw head.
- Slow and Steady: Set your drill to reverse and slowly apply pressure. The bit’s cutting edge might just catch enough of the screw head to unscrew it.
- Pilot Hole for Extractors: Alternatively, you can use a left-hand drill bit to drill a small pilot hole into the center of the stripped screw head, then use a screw extractor.
Left-Hand Threads and Tapping
While less common for the average DIYer, some specialized applications use left-hand threads. In these cases, a tapping drill bit designed for left-hand threads would be used to create the threads by rotating counterclockwise. This ensures that when a left-hand threaded bolt is inserted, it tightens when turned counterclockwise and loosens when turned clockwise.
Choosing the Right Left-Hand Drill Bit
Left-hand drill bits are available in various materials and designs, similar to their right-hand counterparts.
Material Matters
- High-Speed Steel (HSS): The most common and affordable option. Good for general use on metals like steel, aluminum, and wood.
- Cobalt: An alloy of steel with cobalt added. Cobalt bits are harder and more heat-resistant than HSS, making them ideal for drilling tougher metals like stainless steel and cast iron.
- Carbide Tipped: These bits have carbide tips brazed onto a steel body. Carbide is extremely hard and wear-resistant, suitable for very hard materials and high-volume drilling.
Bit Types
- Left Hand Twist Drill Bits: The most common type, featuring spiral flutes that help clear chips.
- Left Hand Screw Extractors: Specifically designed with tapered, reverse threads to grip the inside of drilled holes for extracting broken fasteners.
- Specialty Bits: Some manufacturers offer bits with specific flute geometries or coatings optimized for particular materials or tasks.
Safety First When Using Left-Hand Drill Bits
As with any power tool operation, safety is paramount.
Personal Protective Equipment (PPE)
- Safety Glasses: Always wear safety glasses or a face shield to protect your eyes from flying debris.
- Gloves: Wear sturdy work gloves to protect your hands from sharp edges and heat.
- Hearing Protection: If operating a loud drill for an extended period, consider earplugs or earmuffs.
Safe Drilling Practices
- Secure the Workpiece: Never hold a small workpiece in your hand while drilling. Use clamps or a vise.
- Drill Bit Sharpness: A sharp drill bit cuts more efficiently and generates less heat. Dull bits can break more easily.
- Appropriate Speed: Start at a slow speed and gradually increase if needed. Excessive speed can overheat the bit and the workpiece, leading to damage.
- Lubrication: For drilling metal, use a cutting fluid or oil to reduce friction, cool the bit, and improve chip removal.
- Avoid Overheating: If the bit or workpiece becomes excessively hot, stop drilling and let it cool down.
- Maintain Control: Keep a firm grip on the drill and be prepared for the bit to catch or the material to break free unexpectedly.
Common Problems and Solutions
| Problem | Cause | Solution |
|---|---|---|
| Left-hand bit not removing bolt | Incorrect bit size, poor centering, insufficient pressure | Ensure correct size and centering. Apply steady, firm pressure. Try a slightly larger bit or a screw extractor. |
| Bolt breaks during extraction | Excessive force, brittle bolt material | Use a slow speed and steady pressure. Try a penetrating oil. If it breaks again, you may need to use EDM or a specialty removal service. |
| Bit wanders during drilling | Lack of proper centering, dull bit | Use a center punch accurately. Ensure the bit is sharp. Start with a smaller pilot hole. |
| Bit gets stuck | Binding in the hole, too much pressure | Back the bit out slightly to clear chips. Reduce pressure. Ensure the hole isn’t too deep for the flutes. |
| Overheating of the bit | Too much speed, lack of lubrication | Reduce drill speed. Use cutting fluid or oil for metal. Take breaks to allow the bit to cool. |
Frequently Asked Questions (FAQ)
Q1: Can I use a left-hand drill bit for regular drilling?
A1: While you technically can, it’s not recommended. A standard right-hand drill bit is designed for clockwise rotation, which is optimized for most drilling tasks. Using a left-hand bit in the forward (clockwise) direction of your drill will likely result in poor cutting performance and premature bit wear.
Q2: How do I know if my drill has a reverse setting?
A2: Most modern cordless and corded drills have a switch or button near the trigger that allows you to select forward, reverse, and sometimes a locked position. Look for an arrow indicating the direction of rotation.
Q3: What is the difference between a left-hand drill bit and a screw extractor?
A3: A left-hand drill bit is a cutting tool designed to drill in reverse. A screw extractor (or easy-out) is a tool designed to grip the inside of a drilled hole and unscrew a broken fastener. Often, you use a left-hand drill bit to create a pilot hole for a screw extractor.
Q4: Should I use the same speed for left-hand drilling as for right-hand drilling?
A4: Generally, you should start with a slower speed for left hand drill bit drilling, especially when trying to extract a broken bolt. This allows the bit to bite into the metal effectively and prevents it from camming out. As you gain experience, you can adjust the speed based on the material and the task.
Q5: What if the broken bolt is too hard to drill with a standard left-hand bit?
A5: If you encounter a bolt made of very hard metal, you might need a cobalt or even a carbide-tipped left-hand drill bit. For extremely stubborn fasteners, specialized methods like Electrical Discharge Machining (EDM) might be necessary, or you may need to consult a professional machinist.
Q6: How do I know which size left-hand drill bit to use for a broken bolt?
A6: For removing broken bolts, it’s best to start with a drill bit that is slightly smaller than the diameter of the bolt shank. For instance, if you have a 1/4-inch bolt broken off, you might start with a 7/32-inch or 3/16-inch left-hand drill bit. Many sets of left handed drill bits for removing broken bolts will provide guidance on sizing.
By following this expert guide, you’ll be well-equipped to leverage the unique capabilities of left-hand drill bits, transforming frustrating fastener removal tasks into manageable repairs. Remember to prioritize safety, choose the right tools, and approach the job with patience and precision.