21/64" Thunderbolt® Black Oxide Drill Bit

The Milwaukee 48-89-2727 is a 21/64" Thunderbolt® black oxide jobber drill bit designed for general-purpose drilling in metal, wood, and plastic, typically used for larger bolt and anchor holes in construction and fabrication work.

Key Features

• Black oxide coating – reduces friction and helps resist corrosion
• 135° split point tip – starts on contact and prevents walking for accurate drilling
• Thunderbolt web design (thicker core) – increases strength and resists side-load breakage
• Parabolic flutes – remove chips quickly to reduce heat and improve drilling speed
• 3-flat secure-grip shank – reduces slipping in the drill chuck

Specs

• Size: 21/64 in
• Material: High-speed steel (HSS)
• Finish: Black oxide
• Length: ~4-5/8" jobber length
• Use: Metal, wood, PVC, plastics

Best Uses

• Larger bolt and anchor holes
• Structural metal and fabrication work
• Sheet metal and light steel drilling
• Wood framing and construction
• General jobsite drilling

Bottom Line

The 48-89-2727 is one of the larger “standard workhorse” sizes in Milwaukee’s Thunderbolt line. It’s not a specialty bit—it’s meant for everyday drilling where you need a clean 21/64" hole in common materials, especially in construction and metal fabrication.