3/16 in x 6 in Cobalt Aircraft Extension Drill Bit Pack of 12 - Extra

In this review the Drill America 3/16 in x 6 in Cobalt Aircraft Extension drill bit pack is evaluated for machinists and metalworkers who need reliable performance when drilling tougher alloys. The bottom line: this pack is best for those working with stainless steel, nickel alloys and titanium because the higher cobalt content and a 135 split point produce a steady, self-centering cut that reduces walking and makes deep or hard-material holes far easier to start and finish. It is a practical choice when extra length and durability matter.

Key Features

• Cobalt construction: Higher cobalt content improves performance cutting hard metals such as stainless steel and nickel alloys compared with standard high-speed steel.
• 135 split point tip: The self-centering tip reduces walking and requires less thrust, making hole starts cleaner and more controlled on thin or hard workpieces.
• 6 in overall length: Extra length provides reach for drilling in tight assemblies, deep fixtures or when clearance is limited.
• Round shank: The round shank allows use with a wide variety of tool holding systems including collets and standard drill chucks.
• Gold oxide finish: A thin gold oxide surface treatment resists light corrosion and visually identifies the cobalt tool without changing cutting behavior compared with uncoated drills.

Who It's For

The Drill America GLBCO series is aimed at hobbyists, aircraft and metal fabrication technicians who regularly drill stainless steel, aircraft aluminum, titanium or other high tensile materials and need a bit that will hold an edge and start reliably. Its 6 in length and split point tip suit work on thicker panels, fixtures and assemblies where reach and precise starts matter.

It is less appropriate for casual wood-only work or for users who never encounter hard alloys, where a standard jobber bit can be more economical. Also, those needing non-round shanks for specific quick-change systems should verify holder compatibility before purchase.

Pros & Cons

Pros

• Built for hard metals: cobalt composition and a 135 split point make drilling tough alloys noticeably easier.
• Extra reach: 6 in overall length lets users access deep or awkward drilling locations without extensions.
• Versatile fit: round shanks work with common chucks and collets for broad compatibility.

Cons

• Durability varies by use: some users report mixed long-term wear depending on material and feed rates, so life depends on application and technique.
• Gold oxide is cosmetic/thin: it does not provide a durable coated cutting surface like some advanced coatings.

Specifications

Size	3/16 in x 6 in overall length
Material	Cobalt enhanced high-speed steel
Tip	135 split point (self-centering)
Shank	Round shank for common holders
Surface finish	Gold oxide
Pack quantity	12 pieces

Our Verdict

The Drill America 3/16 in x 6 in cobalt aircraft extension pack is a solid, value-minded choice for anyone who drills stainless, nickel alloys or aircraft materials and needs extra reach. It delivers reliable starts, good drillability and broad chuck compatibility, making it a practical workshop staple for metalworkers who want cobalt performance without specialty coatings.

Frequently Asked Questions

Are these bits good for stainless steel?
Yes. The extra cobalt content and 135 split point are intended to improve cutting and reduce walking in stainless and other hard alloys.

Will the gold oxide act like a coating?
The gold oxide is a thin surface treatment used for identification and slight corrosion resistance but it does not perform like advanced TiN or TiAlN coatings.

Can these be used in a hand drill?
Yes, the round shank fits standard drill chucks, but users should control feed and speed when drilling hard materials to maximize bit life.