What Lubricant To Use When Drilling Metal?

When it comes to metal drilling, the right choice of lubricant can make a world of difference. The process of drilling metal involves high-speed rotation and friction, which can generate intense heat and wear on both the tool and the workpiece. Lubricants play a crucial role in reducing these adverse effects, ensuring smooth drilling operations, prolonging tool life, and enhancing the quality of the final product.

In this comprehensive guide, we will delve into the intricate world of metal drilling lubricants, exploring why they are essential, the types available, and how to choose the most suitable lubricant for your specific needs.

Why Use Lubricants for Metal Drilling?

Drilling metal poses unique challenges due to the hardness and toughness of the materials involved. The friction and heat generated during the drilling process can cause premature tool wear, overheating, and even workpiece damage. This is where lubricants come to the rescue. By forming a protective layer between the cutting tool and the metal, lubricants reduce friction, heat, and wear. The benefits are manifold:

1. Reduced Heat Generation

Friction generates heat, which can result in high temperatures that negatively impact both the tool’s lifespan and the quality of the hole being drilled. Lubricants act as a coolant, dissipating heat and maintaining optimal drilling conditions.

2. Extended Tool Life

Excessive wear on the cutting tool can lead to frequent replacements, adding to operational costs. Lubrication significantly reduces tool wear, resulting in longer tool life and fewer replacements.

3. Improved Hole Quality

Lubricants enhance the accuracy and precision of drilling operations. By reducing friction, they help prevent work hardening and surface irregularities, leading to smoother and more consistent hole surfaces.

4. Enhanced Drilling Speed

With reduced friction, the cutting tool can move more smoothly through the metal, resulting in increased drilling speeds without compromising on hole quality.

Types of Lubricants for Metal Drilling

Before delving into the specifics of lubricants, it’s important to differentiate between cutting fluids and lubricants. Cutting fluids, which include both water-based and oil-based variants, are specifically formulated for metal-cutting operations, including drilling. On the other hand, lubricants are designed to minimize friction and wear during drilling, often tailored to the properties of the metal being drilled. Let’s explore both categories:

Cutting Fluids

Water-Based Cutting Fluids

Water-based cutting fluids are often used for drilling ferrous metals. They offer good cooling properties and are generally cost-effective. However, they may lead to corrosion if not managed properly.

Oil-Based Cutting Fluids

Oil-based cutting fluids provide better lubrication and cooling than water-based variants. They are suitable for a wide range of metals, including stainless steel and aluminum. However, they can be more expensive and require careful disposal due to potential environmental concerns.


Lubricants, unlike cutting fluids, are not always multipurpose. They are formulated to excel in reducing friction during drilling. Here are some types of lubricants commonly used for metal drilling:

Soluble Oils

Soluble oils, also known as emulsifiable oils, are versatile lubricants that can be mixed with water to form an emulsion. They offer good lubrication and cooling properties and are suitable for a variety of metals.

Synthetic Lubricants

Synthetic lubricants are engineered to provide consistent performance across a range of conditions. They have excellent thermal stability and lubricity, making them ideal for high-speed drilling operations.

High-Viscosity Oils

High-viscosity oils are designed for heavy-duty drilling applications. They adhere well to the cutting tool and workpiece, providing effective lubrication even under extreme pressure.

Extreme Pressure (EP) Lubricants

EP lubricants are formulated to withstand the intense pressures and temperatures generated during drilling hard materials like stainless steel. They contain additives that form a protective layer, preventing galling and tool damage.

Can WD-40 Be Used for Metal Drilling?

While WD-40 is a household name and a versatile lubricant, it might not be the best choice for metal drilling. WD-40’s primary purpose is to displace water, prevent rust, and provide light lubrication. However, when it comes to the rigors of metal drilling, it falls short in several areas:

Limited Lubrication Under Pressure

WD-40 is not designed to withstand the high pressures and temperatures generated during metal drilling. It lacks the necessary additives to provide effective lubrication in such demanding conditions.

Quick Evaporation

WD-40 evaporates relatively quickly, especially when exposed to high temperatures. This evaporation can lead to reduced lubrication effectiveness, leaving the cutting tool and workpiece vulnerable to wear.

Lack of EP Additives

Extreme pressure additives are crucial for metal drilling, as they protect the cutting tool from wear caused by the intense pressures at play. WD-40 lacks these additives, making it ill-suited for heavy-duty drilling.

Selecting the Right Lubricant for Metal Drilling

Choosing the right lubricant involves careful consideration of various factors to ensure optimal drilling performance and hole quality. Here are some key points to keep in mind:

Metal Type

Different metals have distinct properties that influence the choice of lubricant. For example:

  • Stainless Steel: Requires a sulfur-free lubricant to prevent work hardening.
  • Aluminum: Benefits from high-lubricity lubricants due to its sticky nature.
  • Hardened Steel: Needs lubricants with extreme pressure additives to withstand the drilling forces.

Drilling Operation

The nature of the drilling operation (e.g., standard drilling, tapping, reaming) affects the lubricant’s requirements. Different operations demand specific lubricant properties for optimal results.

Tool Material

Consider the compatibility between the lubricant and the tool’s material. Certain lubricants may react with certain tool materials, affecting both lubrication effectiveness and tool longevity.

Work Environment

Environmental factors such as temperature variations and the drilling location (indoor or outdoor) can impact lubricant performance. Choose a lubricant that remains stable under the intended working conditions.

Common Lubricant Properties

When evaluating lubricants, pay attention to the following properties:

  • High Viscosity Index: Ensures consistent lubrication even at high temperatures.
  • Extreme Pressure Additives: Essential for withstanding heavy drilling forces.
  • Corrosion Resistance: Protects both the tool and workpiece from corrosion.
  • Thermal Stability: Prevents lubricant breakdown under high temperatures.

Applying Lubricant Effectively

Applying lubricant correctly is as crucial as choosing the right one. Here’s a step-by-step guide to effective lubrication during metal drilling:


  1. Clean and Degrease: Ensure the metal surface is free from dirt, debris, and previous lubricants. A clean surface ensures proper adhesion of the lubricant.
  2. Select Application Method: Choose an appropriate method for applying the lubricant, such as spraying, brushing, or flooding. The method depends on the equipment and the drilling setup.

During Drilling

  1. Continuous Application: Maintain a consistent flow of lubricant during the drilling process. This continuous application ensures that the cutting tool remains properly lubricated throughout.
  2. Monitor Effectiveness: Keep an eye on the drilling process to ensure that the lubricant is effectively reducing friction and heat buildup. Adjust the lubricant flow if necessary.


  1. Clean the Drilled Hole: After drilling is complete, clean the drilled hole to remove excess lubricant and debris. This step ensures the integrity of the hole’s surface.

Best Practices for Metal Drilling with Lubrication

To ensure safe and efficient metal drilling with lubrication, consider these best practices:

Safety Considerations

  1. Ventilation: If drilling is done in an enclosed space, ensure proper ventilation to prevent inhalation of fumes that some lubricants might produce.
  2. Personal Protective Equipment (PPE): Wear appropriate PPE, including gloves and safety goggles, to protect your skin and eyes from direct contact with lubricants.

Regular Maintenance

  1. Equipment Maintenance: Regularly clean and maintain your drilling equipment to ensure optimal performance. Clean tools are more effective at transferring lubricant.

Monitoring and Adjustment

  1. Check Lubricant Levels: Periodically check the lubricant levels during drilling to ensure a continuous flow. Inadequate lubrication can lead to increased friction and heat.
  2. Adjust Application Rate: Depending on the drilling performance, adjust the rate of lubricant application. If you notice increased heat or reduced efficiency, increase the lubricant flow.

FAQs: Choosing the Right Lubricant for Drilling Metal

1. Question: Are lubricants necessary when drilling metal?

  • Answer: Absolutely, using a lubricant when drilling metal is crucial. It reduces friction, heat, and wear on both the drill bit and the metal surface, enhancing the drilling process and prolonging the tool’s life.

2. Question: Can I use water as a lubricant for drilling metal?

  • Answer: While water can provide some cooling, it’s not the best lubricant for metal drilling. Specialized cutting fluids or oils are more effective because they offer superior lubrication and help prevent the drill bit from binding or overheating.

3. Question: What is the best lubricant for drilling stainless steel?

  • Answer: When drilling stainless steel, a sulfur-based cutting oil or a high-performance synthetic lubricant specifically designed for stainless steel is recommended. These lubricants are formulated to handle the unique challenges posed by stainless steel’s hardness.

4. Question: Can I use WD-40 as a lubricant for metal drilling?

  • Answer: WD-40 is not ideal as a drilling lubricant for metals. While it provides some lubrication, it’s not designed to withstand the high pressures and temperatures generated during drilling. It’s better to opt for cutting oils or specialty lubricants.

5. Question: Is it necessary to use a lubricant when drilling softer metals like aluminum?

  • Answer: Yes, using a lubricant is still beneficial when drilling softer metals like aluminum. Lubricants help prevent the aluminum chips from adhering to the drill bit, allowing for smoother and more efficient drilling.

6. Question: Are there any eco-friendly lubricants for metal drilling?

  • Answer: Yes, there are eco-friendly lubricants available for metal drilling. Some manufacturers offer biodegradable cutting fluids that provide effective lubrication while being environmentally conscious.

7. Question: Can I use motor oil as a substitute lubricant for drilling metal?

  • Answer: Motor oil is not recommended as a substitute for proper cutting fluids when drilling metal. Cutting fluids have specific properties to withstand the high heat and pressures generated during drilling, ensuring the best results.

8. Question: What lubricant should I use for high-speed metal drilling?

  • Answer: For high-speed metal drilling, you should use a high-quality synthetic cutting fluid. These fluids are designed to withstand the increased heat generated during high-speed drilling and provide excellent lubrication.

9. Question: Is a lubricant necessary for small-scale metal drilling projects?

  • Answer: Yes, even for small-scale projects, using a lubricant is advisable. It helps maintain the integrity of the drill bit, reduces heat buildup, and makes the drilling process smoother and more precise.

10. Question: Can I use the same lubricant for both drilling and tapping metal?

  • Answer: While some lubricants can work for both drilling and tapping, it’s best to use a lubricant specifically formulated for tapping when performing this operation. Tapping lubricants have unique properties that aid in the threading process.


In the world of metal drilling, lubricants play a pivotal role in ensuring smooth operations, prolonged tool life, and impeccable hole quality. By reducing friction, heat, and wear, these specialized substances contribute to efficient and effective drilling processes. However, choosing the right lubricant requires a deep understanding of the metal being drilled, the drilling operation, and the surrounding conditions. Armed with this knowledge, you can make informed decisions that lead to optimal drilling results.

So, the next time you embark on a metal drilling project, remember that the choice of lubricant isn’t just an afterthought—it’s a critical component that can make all the difference.