Best 5/16 Inch Drill Bit Options for Metal, Stainless Steel and More
Choosing the right 5/16 inch drill bit can impact speed, accuracy, and bit life across metalworking tasks. This guide highlights top cobalt and high-speed steel options designed for metal, stainless steel, and hardened surfaces, with notes on durability, heat resistance, and point design. Each product includes key features to help you compare performance across brands.
Product Summary
| Brand | Model | Diameter | Length | Notes |
|---|---|---|---|---|
| Bosch | CO2147B | 5/16″ | 4-1/2″ | Cobalt M42 alloy, high heat resistance |
| Narwhal | 5/16″ Cobalt Drill Bits (3 Pack) | 5/16″ | 4-5/8″ | M35 cobalt, 135° split point |
| amoolo | 5/16″ Cobalt Drill Bit Set | 5/16″ | 3″ | 10 pieces, M35 cobalt, 135° split point |
| Drill Hulk | 5/16″ Cobalt Steel Bits | 5/16″ | 4-1/2″ | HSS with 5% cobalt, 135° split point |
| Bosch | TI2147IM | 5/16″ | Not stated | Impact Tough™ Titanium Nitride coating |
Bosch CO2147B 5/16 in. X 4-1/2 in. Cobalt M42 Drill Bit
The Bosch CO2147B uses an 8% cobalt M42 alloy to deliver extended life and superior heat resistance. Designed for hard metals including stainless steel and titanium, it maintains cutting performance under high heat. The bit is intended for durable, repeated drilling in challenging materials and features a hardened surface for longer wear life.
Narwhal 5/16 Inch Cobalt Drill Bits (3 Pack)
This 3-pack features M35 cobalt with a 135° split point for easier starting and precision drilling through metal, hardened steel, and stainless steel. Each bit is fully ground for a clean diameter, and the set includes a sturdy plastic storage case for organization and protection during transport and storage.
amoolo 5/16″ Cobalt Drill Bit Set (10pcs)
This 10-piece set uses M35 cobalt for increased wear resistance and durability. Each bit is fully ground with a 135° split point and a straight shank to prevent walking. The kit is suitable for drilling through hard metals, stainless steel, and cast iron, with a plastic box included for neat storage and portability.
5/16-Inch Cobalt Steel M35 Jobber Length Twist Drill Bits
These coils are built with M35 cobalt-steel to provide higher red hardness and durability. The 3-flat shank improves grip and stability, while the 135° split point minimizes walking when drilling into hardened and stainless steel. The bits can be sharpened repeatedly, offering long-term value for heavy metal work.
Bosch TI2147IM 5/16 in. Impact Tough™ Titanium Nitride Coated Drill Bit
The Bosch TI2147IM features a Titanium Nitride coating for reduced friction and longer life in heavy-use scenarios. It’s designed for impact drilling with longer flutes to improve material removal and reduce clogging during challenging metal drilling tasks. The no-skate tip helps with accurate starts on tough metals.
Buying Guide: 5/16″ Drill Bits For Metalworking
- Material composition: Cobalt alloys (M35, M42) provide superior heat resistance and longer life when drilling stainless steel, cast iron, and hardened metals. Titanium nitride coatings can further reduce friction and improve wear life for some applications.
- Point geometry: A 135° split point helps reduce walking and improves start-up accuracy, especially in hard metals. Fully ground edges ensure precise diameters and cleaner starts.
- Shank and fit: Look for straight or traditional round shanks for compatibility with most drill chucks. Some sets include three-flats or other shank designs for stability in high-torque conditions.
- Length vs. reach: Jobber-length bits (around 4 inches) are versatile for general metal drilling, while longer sets are useful for deeper holes in metal blocks or structural components.
- Kit organization: Storage cases keep bits organized and protected, reducing loss and maintaining edge alignment for repeated use.
- Application suitability: For stainless steel, titanium, or hardened aluminum, prefer cobalt-grade bits with appropriate coatings. For softer metals, standard high-speed steel with the right geometry can suffice; however, cobalt bits offer longer life in tougher materials.
- Maintenance: Sharpening cobalt bits is possible but requires careful grinding to preserve the 135° point and primary cutting edges. Avoid overheating during sharpening to prevent micro-fractures.
- Cost vs. value: Cobalt bits cost more upfront but typically last significantly longer in tough metals, reducing replacement frequency in professional use.