Milwaukee 48-20-4390 Spline Rotary Hammer Drill Bit

Product Description

The MILWAUKEE 48-20-4390 is a spline-shank rotary hammer drill bit engineered for drilling through brick, block, concrete, and reinforced concrete. Built around a 4-cutter tip with a 4 x 90-degree geometry, this bit resists lock-up when it contacts rebar — a common cause of downtime and bit failure on concrete work. The 1-1/8 inch diameter head pairs with a high-volume flute that clears debris quickly, reducing heat buildup and keeping penetration rates consistent. At 22 inches overall length with a 17-inch drilling depth, it handles thick slabs and deep anchor holes. Licensed electricians, plumbers, and concrete contractors running spline-drive rotary hammers are the primary users.

This bit is designed for use in spline-drive rotary hammers on jobsites where drilling through reinforced concrete, CMU block, or brick is a routine task. The patented rebar chamfers on the 4-cutter head add durability in rebar-heavy pours where standard two-cutter geometry tends to deflect or seize. Typical applications include anchor bolt holes, conduit penetrations, sleeve installations, and core layout work in commercial and residential construction.

Key Features

• 4-cutter 4 x 90-degree tip geometry resists lock-up when drilling through rebar
• Patented rebar chamfers extend bit life in reinforced concrete
• High-volume flute promotes fast debris evacuation and reduced heat
• 1-1/8 inch diameter with a 17-inch drilling depth
• 22-inch overall length for thick-slab and deep-hole applications
• Spline shank for use with spline-drive rotary hammers

Compatibility

Designed for use with spline-drive rotary hammers. Suitable for drilling brick, block, concrete, and reinforced concrete.

Installation Notes

Installation of this bit requires a spline-drive rotary hammer — confirm shank compatibility before use. Wear appropriate PPE including eye protection and hearing protection when operating rotary hammer equipment. Inspect the bit for wear or damage before each use and replace if the cutters or flute show signs of significant deterioration. Follow applicable OSHA and site safety requirements for concrete drilling operations.

Technical Specifications

• Shank Type: Spline
• Tip Geometry: 4-cutter, 4 x 90 degrees
• Bit Diameter: 1-1/8 inches
• Drilling Depth: 17 inches
• Overall Length: 22 inches
• Weight: 2.73 pounds

Standard Information

• Brand: MILWAUKEE
• Manufacturer Part Number: 48-20-4390