Drill America #78 Cobalt Heavy Duty Drill Bit Pack of 12 - Cuts Tough

In this review the Drill America #78 Cobalt Heavy Duty Drill Bit pack is assessed for machinists and serious DIYers who need reliable drilling into high tensile materials. The bottom line: these bits are built from cobalt steel to hold hardness and sharpness longer than standard high-speed steel, making them a sensible choice when drilling stainless steel, inconel or other tough alloys. The pack of 12 jobber length bits offers good value for a workshop set where tougher metals are common, and the review focuses on performance, durability, and practical use on bench and jobsite drills.

Key Features

• Cobalt steel construction: Provides higher red hardness so the bits maintain cutting edge at elevated speeds when working with hard alloys.
• Gold oxide finish: A thin oxide layer helps identify the bits and keeps performance similar to uncoated tools while resisting minor corrosion.
• Round shank: Allows use with a wide variety of chucks and toolholding systems for quick bit changes.
• Spiral flute design: Right-hand cut flutes evacuate chips up and out of the hole to reduce clogging during deep drills.
• 118 degree point: A standard point angle that balances centering and cutting speed for general metalworking tasks.
• Manufactured to NAS 907: Made to an aerospace standard indicating consistent geometry and quality control for repeatable results.

Who It's For

This pack is best for metalworkers, maintenance technicians, and serious hobbyists who frequently drill stainless steel, nickel alloys, titanium, or other high tensile materials where ordinary HSS bits wear quickly. Shops that need a reliable, ready-to-use set of jobber length bits will appreciate the combination of toughness and familiar geometry.

Those who primarily drill soft metals, wood, or plastics may find these overbuilt and could save cost with plain HSS bits. If the highest possible hole quality at extreme production speeds is required, solid carbide drills might be a better fit for sustained high-volume machining.

Pros & Cons

Pros

• Excellent durability and sustained cutting performance when drilling hard metals thanks to cobalt alloy.
• Good value for the pack of 12, delivering multiple sizes or spares for a busy shop.
• Sharpness out of the box and ability to run at higher speeds than HSS yields faster work in tough materials.
• Consistent manufacturing to aerospace standard improves repeatability across the set.

Cons

• The gold oxide is a very thin surface treatment, so users should not expect the same wear resistance as modern coated drills designed for long production runs.
• Round shank limits positive locking in some collet systems compared with precision ground shanks.

Specifications

Series	D/ACO
Material	Cobalt steel
Point Angle	118 degrees standard point
Finish	Gold oxide (thin)
Shank Type	Round shank
Length	Jobber length
Manufacturing Standard	National Aerospace Standard 907

Our Verdict

The Drill America #78 cobalt jobber set is a practical, cost-effective choice for anyone who needs dependable drilling in hard metals without stepping up to carbide. Its higher red hardness, sharpness, and aerospace-level consistency make it a smart workshop staple for maintenance and low-to-medium volume metalwork. Buy this set for tougher alloys; choose coated or carbide options for heavy production environments.

Frequently Asked Questions

Are these bits suitable for stainless steel?
Yes, the cobalt steel composition is specifically effective for drilling stainless steel and other high tensile alloys.

Can they be used in cordless drill drivers?
Yes, they can be used in corded or cordless drills, but maintain proper speed and feed to avoid overheating and premature wear.

Do they come coated for extra wear resistance?
The bits have a thin gold oxide surface treatment that is mostly identification and slight protection; it performs similarly to uncoated tools rather than heavy industrial coatings.