Cobalt Heavy Duty Drill Bits Pack of 12 - Durable Jobber Length

Our review of the Drill America #79 D/ACO series finds these cobalt heavy duty drill bits best suited for metalworkers and fabricators who need a reliable jobber length bit for tough alloys. The single biggest reason to buy is durability: made from heat resistant cobalt steel they hold their edge far longer than typical high-speed steel bits and permit higher operating speeds, making them a straightforward choice when drilling stainless steel, nickel alloys or other high tensile materials.

Key Features

• Cobalt steel construction: Provides higher red hardness so the bits stay sharp longer when cutting hard metals such as stainless steel and inconel.
• Gold oxide surface: A thinner oxide finish resists corrosion without changing cutting performance, so users get durable bits with consistent results.
• 118 degree standard point: Offers a balanced cutting geometry suitable for general purpose drilling and good centering on a variety of materials.
• Right-hand spiral flute: Evacuates chips up and out of the hole when run clockwise, helping reduce clogging in deeper cuts.
• Round shanks: Fit a wide variety of chucks and toolholding systems for easy tool changes in drills and drill presses.
• Manufactured to NAS 907: Built to an aerospace standard that indicates consistent tolerances and quality across the pack.

Who It's For

These drill bits are ideal for professional tradespeople, machinists and advanced hobbyists who frequently drill stainless steel, titanium, inconel or other high strength metals where standard HSS bits wear quickly. The pack of 12 gives small shops and job-site crews enough replacement bits to keep projects moving without frequent reorders.

Casual DIYers who only drill occasional soft materials may not need the added expense of cobalt bits and could look to standard HSS or coated bits instead; also users who require specialty point geometries for sheet metal or masonry should choose a purpose-made bit rather than this general 118 degree jobber bit.

Pros & Cons

Pros

• Excellent durability and sharpness retention when cutting high tensile metals.
• Permits higher cutting speeds than standard HSS, improving productivity on tough jobs.
• Pack of 12 ensures spare bits are available during longer projects.
• Round shanks and standard point geometry make the bits versatile for many toolholders and setups.

Cons

• Angle feedback is mixed among users, so for highly specialized angles or split points a different bit may be preferable.
• Gold oxide is mainly cosmetic compared with more advanced coatings, so it does not provide the same heat resistance as specialized coatings.

Specifications

Series	D/ACO (Drill America #79)
Material	Heat resistant cobalt steel
Point angle	118 degrees standard point
Surface finish	Gold oxide
Shank type	Round shank
Standards	Manufactured to National Aerospace standard 907
Pack quantity	12 bits

Our Verdict

For anyone who regularly drills tough, high tensile materials the Drill America D/ACO cobalt jobber bits represent good value: they cut cleaner, last noticeably longer than standard HSS, and are built to a consistent aerospace standard. Buy them if you want durability and predictable performance on stainless and alloy work; casual users working only with soft metals can opt for less costly alternatives.

Frequently Asked Questions

Are these bits suitable for stainless steel?
Yes, the cobalt steel construction and higher red hardness make them well suited for stainless steel and other hard alloys.

Will the gold oxide change drilling performance?
No, the gold oxide is a thin surface treatment that resists corrosion but performs similarly to uncoated tools in cutting.

Do these require a specific chuck or holder?
No, the round shanks are compatible with a wide range of chucks and toolholding systems, but confirm chuck capacity for the bit size used.