5/16" Thunderbolt® Black Oxide Drill Bit

The Milwaukee 48-89-2726 is a 5/16" Thunderbolt® black oxide jobber drill bit used for general-purpose drilling in metal, wood, and plastic, and it’s one of the larger common “workhorse” sizes in Milwaukee’s standard bit lineup.

Key Features

• Black oxide coating – reduces friction and improves corrosion resistance
• 135° split point tip – starts on contact and helps prevent walking for accurate holes
• Thunderbolt web (reinforced core) – adds strength and reduces breakage under side load
• Parabolic flute design – clears chips quickly to reduce heat buildup
• 3-flat secure-grip shank – helps prevent slipping in the drill chuck

Specs

• Size: 5/16 in
• Material: High-speed steel (HSS)
• Finish: Black oxide
• Length: ~4-1/2" jobber length
• Use: Metal, wood, PVC, plastics

Best Uses

• Larger bolt and anchor holes
• General construction and fabrication work
• Sheet metal and light structural steel
• Wood framing and heavy-duty DIY projects
• Everyday jobsite drilling

Bottom Line

The 48-89-2726 is a standard large-size general-purpose drill bit, not cobalt or specialty. It’s designed for reliable 5/16" holes in common materials, especially when you’re working at construction or fabrication scale.