What Is the Best Drill Bit for Stainless Steel? [2025 Edition]

In the field of machining, stainless steel is widely recognized as a “high-strength, difficult-to-machine” metal. Due to its excellent corrosion resistance and high toughness, stainless steel demands higher standards in the drill bit’s material, geometry, coating, and chip evacuation design during drilling. Choosing the best drill bit for drilling stainless steel directly impacts machining efficiency, hole quality, tool life, and overall cost control.

The market offers a variety of drill bits for stainless steel, ranging from traditional high-speed steel (HSS) bits to cobalt alloy drills, and high-end tungsten carbide bits. Each type has its specific applications and limitations. Different stainless steel grades—such as 304 and 316 austenitic stainless steels—also exhibit distinct machining characteristics. Selecting the right tool based on the material and matching it to the machining equipment is essential knowledge for any processing engineer.

This article explores stainless steel’s material properties and provides a comprehensive analysis of mainstream drill bit types, structural designs, coating technologies, and their performance in stainless steel machining. Coupled with industry trends and 2025 application scenarios, it helps readers understand what truly constitutes the best drill bit for stainless steel, enabling more informed and efficient choices for CNC or manual drilling.

Why Do Stainless Steel Drilling Require Special Drill Bits?

Many engineers underestimate stainless steel’s complexity when drilling. Austenitic stainless steels like 304 and 316, due to their unique microstructure and mechanical properties, impose significantly higher loads on the tool compared to carbon steel or aluminum. Choosing drill bits specifically designed for stainless steel is critical to ensuring quality, extending tool life, and reducing costs.

Processing Characteristics and Challenges of Stainless Steel

• Severe work hardening: Stainless steel work hardens rapidly after contact with the drill, increasing cutting resistance and accelerating tool wear.

• Heat concentration: Poor thermal conductivity causes heat to accumulate at the cutting zone, leading to drill overheating, annealing, and loss of hardness.

• Difficult chip evacuation: Tough stainless steel generates long, stringy chips that, if not properly evacuated, cause tool jamming, surface damage, or drill breakage.

Because of these challenges, conventional drill bits (e.g., standard HSS) often fail in stainless steel machining. Priority should be given to cobalt alloy or coated carbide drill bits that can handle high heat, pressure, and work hardening.

Why Ordinary Drill Bits Are Often Inadequate

Common issues when using standard drill bits on stainless steel include:

• Premature tool degradation: Poor heat resistance causes edge annealing at elevated temperatures, reducing cutting effectiveness.

• Slipping and poor positioning: Inappropriate tip angle or dullness causes slipping on the stainless steel surface, leading to off-center holes.

• Poor hole quality: Inefficient chip removal and continued use after tool wear cause rough hole walls, increased burrs, and eccentricity.

These problems reduce efficiency, increase tool consumption, and raise rework costs. Thus, using stainless steel-specific drill bits with heat resistance, high surface hardness, and optimized geometry (e.g., 135° split-point cobalt drills, TiAlN-coated carbide drills) significantly improves stability and accuracy.

What Are the Common Types of Stainless Steel Drill Bits?

To achieve ideal drilling results on stainless steel, choosing drill bits with high wear resistance, excellent heat resistance, and compatibility with various equipment is vital. The most common categories include:

Cobalt Alloy Drill Bits

Cobalt alloy drills, typically HSS-Co, are the most widely used for stainless steel. They offer excellent red hardness and wear resistance, suitable for continuous drilling of high-strength metals.

• M35 cobalt drill (5% cobalt): Cost-effective, suitable for 304, 321 stainless steel.

• M42 cobalt drill (8% cobalt): Higher hardness and heat resistance, ideal for harder materials like 316 stainless steel and heat-treated parts.

Cobalt drills resist annealing at high temperatures, prolonging tool life. They are common in bench drills, vertical drills, semi-automatics, and some CNC scenarios.

Tungsten Carbide Drill Bits

Solid carbide drills feature extremely high hardness and wear resistance, ideal for high-speed, high-precision stainless steel machining, especially on CNC machines.

They excel in automated, high-intensity cutting and deep-hole drilling, significantly boosting productivity for mass-produced 304 and 316L parts. However, they are brittle and require rigid machines and proper cooling to avoid chipping and breakage.

Recommendations: Use carbide drills with internal cooling or external mist/oil spray to maximize tool life.

Coated HSS Drill Bits (TiN/TiAlN)

For light loads, small batches, or manual drilling, coated HSS drill bits provide a cost-effective alternative.

• TiN coating: Increases surface hardness, reduces friction.

• TiAlN coating: Offers superior heat resistance, suited for intermittent cuts or minimal lubrication environments.

Coated HSS drills outperform uncoated variants in temperature control and chip evacuation but are less suited for high-speed, deep-hole, or batch drilling. Ideal for hand drills, manual bench drills, and DIY applications.

Summary and Recommendations

• For heat resistance and cost efficiency: prefer cobalt alloy drills (M35, M42 series).

• For high-speed, precise, and efficient drilling: select tungsten carbide drills.

• For light load and manual drilling: coated HSS drills (TiN/TiAlN) work well.

How to Choose the Best Drill Bit for Drilling Stainless Steel?

Selecting the best drill bit for stainless steel requires a systematic approach based on processing method, material grade, and drill bit design.

Consider the Processing Method: Manual vs. CNC

• Manual/Handheld Drilling:
  Limited rigidity and simpler cooling mean you should choose tough, cost-effective bits such as M35/M42 cobalt drills or TiN-coated HSS bits. These tolerate operational variation well and suit DIY or small batch tasks.

• CNC Machining:
  With superior rigidity and cooling, CNC machines benefit from carbide drills for high-speed, efficient drilling, especially for deep or batch holes. Cobalt drills with internal cooling also perform well in medium-speed, stable feed setups. These are optimal for 304/316 stainless steel, delivering precise holes and extended tool life.

Consider the Workpiece Material: 304, 316, and Other Grades

• 304 Stainless Steel:
  High ductility but prone to work hardening. M35 cobalt and TiAlN-coated drills work well to manage heat and wear.

• 316/316L Stainless Steel:
  Contains more nickel and is harder to machine. M42 cobalt or solid carbide drills with double chip flutes optimize chip removal and reduce heat buildup.

Consider Drill Bit Design

• Drill Tip Angle:
  135° tip angle with split-point design improves penetration, reduces slipping, and provides precise positioning without pre-drilling.

• Blade Shape:
  Cross grinding enhances sharpness and prevents sliding on smooth stainless steel surfaces, improving hole quality.

• Chip Flute Design:
  Double flute or U-shaped grooves with coatings reduce friction and improve chip evacuation, critical given stainless steel’s long stringy chips.

Recommended Brands and Models of the Best Drill Bits for Stainless Steel in 2025

Stainless steel machining demands exceptionally high tool performance. Choosing reputable brands and the right models is key to ensuring process success, boosting efficiency, and extending tool life. Below are three mainstream categories of stainless steel-specific drill bits, recommended by processing method and application scenario. These serve as useful references for CNC engineers, purchasing managers, and shop floor operators.

Professional-Level Recommendations (For CNC Use)

In CNC machining centers and high-precision automation, drill bits must withstand high cutting forces and continuous high temperatures while maintaining red hardness, chip evacuation, and dimensional stability. The following brands and models are widely used in mid-to-high-end workshops and batch manufacturing.

• Samho M42 Cobalt Alloy Drill
  Type: HSS-Co (8% cobalt)
  Features: Excellent heat resistance, 135° split-point tip with cross grinding, ideal for 304/316 stainless steel drilling.
  Applications: Medium-speed, rigid machines; deep hole and intermittent drilling.
  Why Recommended: Known for superior edge treatment and wear resistance, Samho offers cost-effective, stable performance under medium loads, making it a preferred cobalt drill for stainless steel.

• Walter & Guhring Carbide Drills
  Type: Solid carbide, some with internal coolant channels.
  Features: High-speed, efficient cutting optimized for batch stainless steel processing.
  Applications: Automated tool changers, deep-hole drilling, high-speed dry machining.
  Why Recommended: These German brands represent high-end tooling with superior durability and precision, especially suited for high-frequency continuous production environments.

General-Purpose Recommendations (For Hand Drills)

For small to medium shops, DIY users, or maintenance work typically involving electric or bench drills with lower rigidity, drills need good toughness, easy positioning, and chip resistance.

• DEWALT Cobalt Drill Set (Pilot Point Design)
  Type: M35 cobalt, 135° split-point.
  Features: Fast drilling with anti-slip design, suitable for manual stainless steel drilling.
  Applications: Equipment installation, maintenance, light metal processing.
  Why Recommended: Offers reliable positioning and durability, popular with individual users and small workshops.

• Bosch TiN Coated High-Speed Steel Drill
  Type: HSS with TiN coating.
  Features: Reduces friction, enhances hardness, suitable for short-term medium-strength stainless steel drilling.
  Applications: Intermittent drilling, maintenance, general-purpose tasks.
  Why Recommended: Known for cost-effectiveness, Bosch drills provide stable performance for occasional users and light workloads.

Dedicated High-End Solutions (Deep Hole, High-Speed, Automation)

For demanding applications like high-speed batch production, deep holes, and aerospace-grade parts, traditional drills fall short. Specialized tools with internal cooling, replaceable inserts, and advanced designs become necessary.

• Kennametal Internally Cooled Carbide Drill (KenDrill™ Series)
  Type: Solid carbide with coolant-through design.
  Features: High-speed drilling, excellent chip evacuation and cooling, compatible with MQL/high-pressure coolant.
  Applications: CNC deep-hole drilling, precision mold holes, medical device manufacturing.
  Why Recommended: Widely used in aerospace and automotive sectors, KenDrill significantly reduces drill breakage and hole deviations.

• Sandvik Indexable Drill (CoroDrill Series)
  Type: Replaceable insert drill with internal cooling.
  Features: Suitable for batch standard hole machining, low maintenance, versatile across materials.
  Applications: Multi-station CNC lines, automated drilling, smart manufacturing.
  Why Recommended: Sandvik’s drills excel in chip control and flexibility, ideal for complex holes and high-efficiency processes.

 

Practical Suggestions for Processing Stainless Steel

Even with the right drill bit, machining quality depends heavily on cutting parameters, cooling methods, and operator techniques. In hard-to-machine stainless steels like 304 and 316, improper handling can cause premature drill failure and poor hole quality. Key practical tips include:

Drilling Speed and Feed Parameters

Proper spindle speed and feed rates balance tool life and process stability. Avoid the misconception of “higher speed, lower feed.”

• Example for cobalt drills (M35/M42):

  • Recommended surface speed: 15–25 m/min.

  • For a 6mm drill, ~800–1200 RPM spindle speed.

  • Feed rate: 0.05–0.15 mm/rev (machine rigidity dependent).

Notes:
Excessive speed degrades red hardness, causing annealing and wear. Too low feed leads to heat build-up and chipping. Use constant surface speed (CSS) control on CNC machines for consistency.

Cooling Method and Cutting Fluid Selection

Stainless steel’s low thermal conductivity causes heat concentration, leading to overheating and burns. Proper cutting fluid and cooling method extend tool life and improve hole quality.

• Water-soluble coolant: General purpose, strong cooling, cost-effective.

• Semi-synthetic coolant: Combines cooling and lubrication, suitable for medium/high-strength stainless.

• Fully synthetic (microemulsion): Superior lubricity at high temps, recommended for carbide drills and high-speed drilling.

Cooling techniques:

• External spray/oil mist for hand and bench drills.

• Internal coolant-through for CNC and deep-hole drills.

• Manual drip oil cooling as supplemental method if no system available.

Common Problems and Solutions

• Slipping & Mispositioning:

  • Use center punch for stable starting point.

  • Choose 135° split-point drills with cross-edge design.

  • Lower initial RPM to prevent sliding (“polishing”).

• Burning or Discoloration:

  • Reduce speed, increase feed to avoid friction-dominant cutting.

  • Enhance cooling and lubrication, use TiAlN coated drills.

• Chipping or Breakage:

  • Ensure rigid fixturing and stable setup to minimize vibration.

  • Shorten drill overhang length.

  • Use carbide drills with chip breakers for improved chip evacuation and toughness.

What Is the Best Drill Bit for Stainless Steel?

In high-load, high-temperature stainless steel drilling, no “one-size-fits-all” drill bit exists. Instead, selection must align with your equipment, working conditions, and material type to optimize efficiency, tool life, and hole accuracy.

• By machining method:

  • CNC: Solid carbide or internally cooled cobalt drills for high hardness and chip control, ideal for batch deep holes and 316 stainless steel.

  • Manual/Bench drills: M35/M42 cobalt or TiN coated HSS drills with toughness and anti-chipping strength, perfect for smaller shops and maintenance.

• By material:

  • 304 stainless steel: M35 cobalt or TiAlN coated HSS drills balance efficiency and cost.

  • 316/321 stainless steel and high-nickel grades: M42 cobalt or carbide drills improve heat resistance and stability.

• By drill geometry:

  • 135° split-point tip prevents slipping, enhances positioning.

  • High-performance coatings (TiAlN, TiCN) reduce friction and temperature.

  • Wide/double spiral flutes optimize heat dissipation and chip removal.

• Operational parameters:

  • Use low speed, moderate-to-high feed.

  • Select suitable coolant and ensure sufficient cooling.

  • Adjust drill geometry and machining strategy if issues arise.

Best Practice: The “best drill bit” is the one validated by your actual equipment and workpieces through testing and parameter tuning. Combining high-quality brand selection with optimized cutting strategies enables safe, efficient, and sustainable stainless steel drilling.

FAQ: What You Must Know About Stainless Steel Drill Bits

Q: What brand of drill bits is best for drilling stainless steel?
A: Leading brands include Samho, Walter, Guhring, Kennametal, Sandvik, DEWALT, and Bosch. They offer cobalt, carbide, and coated HSS drills optimized for 304 and 316 stainless steels. Choose based on equipment type and processing needs.

Q: Is cobalt or carbide drill bit necessary for stainless steel?
A: Cobalt (M35/M42) and carbide drills are mainstream due to superior heat resistance and durability. However, for light or occasional manual drilling, coated HSS drills (TiN/TiAlN) can suffice if used with correct parameters.

Q: Why does my drill burn out quickly?
A: Usually caused by excessive heat due to high speed, low feed, or poor cooling. Solutions include reducing speed, increasing feed, using proper coolant, and selecting suitable drill bits.

Q: Can I use a hand drill to drill stainless steel?
A: Yes, if using proper drill bits like M35 cobalt or TiN-coated HSS, with correct low-speed, moderate feed parameters, plus center punch positioning and adequate cooling.