25/64" Thunderbolt® Black Oxide Drill Bit

The Milwaukee 48-89-2731 is a 25/64" Thunderbolt® black oxide jobber drill bit used for general-purpose drilling in wood, metal, and plastic. It’s one of the larger standard sizes in Milwaukee’s Thunderbolt line.

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 reinforced web – thicker core improves strength and reduces breakage under load
• Parabolic flute design – clears chips quickly to reduce heat and improve drilling speed
• 3-flat Secure-Grip shank – helps prevent slipping in the drill chuck

Specs

• Size: 25/64 in (0.3906")
• Material: High-speed steel (HSS)
• Finish: Black oxide
• Length: ~5-1/8" jobber length
• Use: Metal, wood, PVC, plastics

Best Uses

• Larger bolt and anchor holes
• Structural metal fabrication
• Construction framing work
• Sheet metal and light steel drilling
• General shop/jobsite drilling

Bottom Line

The 48-89-2731 is a large standard “workhorse” drill bit, not a cobalt or specialty bit. It’s part of Milwaukee’s basic black oxide lineup meant for everyday drilling where you need a clean 25/64" hole in common materials.