Drill bits designed for hardened steel require materials and geometries that resist heat, wear and chipping. This guide highlights five Amazon-listed sets that are well-suited to stainless steel, hardened metals, cast iron and related materials. Each entry synthesises coatings, cobalt content, tip design and shank compatibility to help you choose the right bit for robust metalworking tasks in the UK workshop.
Product Overview
| Product | Brand | Key Strength |
|---|---|---|
| Metric M42 8% Cobalt Twist Drill Bits Set | STROTON | High hardness, fast cutting in stainless steel |
| 13Pack HSS Twist Drill Bit Set M35 | JTWEB | Very high heat resistance, fast cutting |
| 4-10mm HSS Cobalt Drill Bit Set | Rennie Tool Company | Wide size range, durable cobalt construction |
| HPMAISON True 5% Cobalt Set | HPMAISON | 135° split point, strong heat resistance |
| Bosch Professional 25-Piece PointTeQ Set | Bosch | ProBox organisation, efficient metal drilling |
Notes: All products are listed with their official Amazon pages. This guide focuses on cobalt and high-speed steel (HSS) drill bits suitable for hardened metals, stainless steel, cast iron and related materials commonly encountered in UK workshops.
Cobalt Bits For Tough Metals
This STROTON set uses premium M42 8% cobalt steel with a Rockwell hardness rating around 68-70 HRC. Cobalt content provides heat and wear resistance ideal for stainless steel, hardened metals and other tough materials. The 3-step cutting geometry aims to reduce chipping and prolong tool life, enabling faster material removal with lower overall tool wear. Applications span from stainless steel to harder metals and even certain plastics and aluminium. While cobalt bits generally command a higher upfront cost, their durability lowers cost per hole in demanding tasks.
Features include: heat resistance under heavy use, chip resistance and long tool life; a design intended to cut through stainless steel and hard metals efficiently; and claims of faster cutting speeds when used within recommended RPM ranges. Suitable for pillar drills and standard drill chucks when paired with the correct torque, speed and clamping.
Precise M35 HSS Twist Bits
These JTWEB bits are manufactured from M35 cobalt steel, combining molybdenum and cobalt for a hardened alloy with Rockwell hardness up to 67. The kit features 135° quick-cut points that are self-centering, enabling rapid entry with less pressure and minimal walking. The straight shank is compatible with standard drill chucks, reducing vibration and improving alignment. They are designed for high-temperature performance and longer life compared with ordinary HSS bits, claiming up to twelve times longer life in some comparisons. Prolonged use in hard metals benefits from high heat resistance and robust edge retention.
Considerations include RPM recommendations (often around 1500 RPM or higher for optimal efficiency), the need for steady feed pressure to avoid premature wear, and ensuring the drill bit set is suitable for your drill’s chuck size and power. This set aims to balance speed, longevity and versatility across wood, metal and plastic tasks. It is well-suited for metalworking projects requiring durable, fast-cutting bits.
Versatile 4-10mm Cobalt Set
Rennie Tool Company offers a 5-piece HSS cobalt drill bit set with sizes 4, 5, 6, 8 and 10 mm, housed in a plastic case for convenient storage. The bits use M35 cobalt steel for enhanced hardness, heat resistance and durability when drilling stainless steel, cast iron, hard metals and plastic. A 135° split point reduces walking and produces clean entries, contributing to efficient and precise drilling. The set’s versatility makes it suitable for pillar drills, handheld drills and even CNC machines, provided the machine’s spindle torque and RPM are appropriate for cobalt cutting tools.
Practical considerations include how often you encounter materials such as stainless steel or hardened alloys, the ease of storage and how the set complements other drill bit ranges in your collection. For projects involving repetitive holes in tough metals, this range provides a compact yet capable option that focuses on reliability and accuracy.
Five Percent Cobalt High-Performance Set
HPMAISON’s 5% cobalt set consists of 13 pieces from 1.5 to 6.5 mm, designed to withstand high temperatures and heavy use. The bits emphasize a DIN338 compliance with precise 135° split points for reduced walking and efficient chip removal. The gold oxide finish enhances oxidation resistance, while straight shanks ensure compatibility with standard chucks. The design targets stainless steel, cast iron and other hard materials, with the 135° point aiding quick entry and stable drilling in challenging workpieces. The kit aims to deliver reliable performance across metal and certain hard plastics, especially where heat buildup is a concern.
Buyers should consider RPM guidelines, material compatibility, and whether the set covers the sizes you frequently need. The storage box aids organisation, making it easier to identify the right size during a project and reducing the risk of dulling a bit by using the wrong tool for a job.
Professional Metal Drill Bit Set
Bosch’s 25-piece PointTeQ ProBox set claims faster drilling in metal thanks to the PointTeQ tip design, which reduces heat generation and wear during cutting. The cylindrical shank is compatible with three-jaw drill chucks, making it a flexible option for most standard drills. The kit is designed to optimise drilling speed and efficiency in metal applications, with corporate-brand reliability and a storage solution that helps keep bits aligned with their sizes and intended materials. This set covers a wide spectrum of metals and provides a practical balance between performance and convenience for professional or serious DIY users.
When evaluating this set, consider the intended use (heavy metal work vs. lighter metal tasks), chuck compatibility, and whether the included sizes align with your typical project requirements. The ProBox packaging helps keep tools organised and accessible between jobs, which can improve workflow in a busy workshop environment.
Buying Guide: Key Purchase Considerations
- Material composition: Cobalt content (5%–8%) increases heat resistance and edge retention, which is beneficial for hardened steel and stainless alloys. Higher cobalt often means longer life but at a higher upfront cost.
- Tip geometry: Split point or 135° tips help reduce walking and allow faster starts, especially in hard metals. Self-centering tips are advantageous when precision is critical.
- Shank compatibility: Ensure the shank type matches your drill chuck (straight shank is common for standard chucks; hex shanks may require specific adaptors).
- Working RPM: Many cobalt and HSS cobalt bits require higher RPM to achieve optimum performance. Respect manufacturer guidance to avoid bit wear or failure.
- Size range: For comprehensive metalwork, sets offering a range from small to mid sizes (e.g., 1.5–10 mm) reduce the need for buying individual bits over time.
- Storage and organisation: A sturdy case or box helps prevent loss and keeps bits sharp by reducing contact with unwanted debris or moisture.
- Application scope: Some sets are tailored for stainless steel and hardened metals, while others are more generalist. Align the selection with your typical materials and projects.
- Tool life and cost per hole: While cobalt bits may cost more upfront, their durability can lower the cost per drilled hole in demanding tasks.
Overall guidance suggests selecting a set that balances material strength (cobalt content), practical size range, and compatibility with your existing drill system. For UK workshops handling stainless steel and other hardened alloys, these five selections provide options that cover fast cutting, longevity and versatile sizes across common drill bit tasks.