Irwin 91133 Reduced Shank Drill Bit 33/64 in Hss Weldon

Product Description

The IRWIN 91133 is a reduced shank twist drill bit designed for drilling through metal and other materials where a full-shank bit would exceed the chuck capacity. It carries a 33/64 inch cutting diameter on a 1/2 inch Weldon flat shank, allowing it to seat in standard 1/2 inch chucks and driven-tool holders without slipping. The bit is ground from high-speed steel (HSS) with an oxide finish that provides light corrosion resistance and helps reduce friction during drilling. At 6 inches overall length, it gives machinists and tradespeople the reach needed for deeper-clearance applications while keeping the shank size manageable.

This drill bit is suited for metal fabrication shops, mechanical contractors, and maintenance technicians who work with drill presses, milling machines, or heavy-duty hand drills equipped with 1/2 inch chucks. The 118-degree standard point angle makes it appropriate for general-purpose work in mild steel, aluminum, and similar materials. The Weldon flat shank with three flats resists rotation in set-screw-style tool holders, making it a reliable choice for production drilling setups where bit slippage is a concern.

Key Features

• 33/64 inch cutting diameter on a reduced 1/2 inch Weldon flat shank — fits standard 1/2 inch chucks
• High-speed steel construction for durability in general-purpose metal drilling
• 118-degree standard point angle for broad material compatibility
• Oxide finish reduces friction and provides light corrosion resistance
• Three-flat Weldon shank prevents rotation in set-screw tool holders
• Right-hand cut with regular spiral, two-flute design for efficient chip evacuation

Compatibility

Designed as a general-purpose reduced shank drill bit for use in 1/2 inch Weldon flat set-screw tool holders, drill press chucks, and compatible milling machine collet systems that accept 1/2 inch shank tooling.

Installation Notes

Installation and use should be performed by qualified machinists or tradespeople familiar with rotary cutting tools and applicable shop safety practices. Ensure the drill press or driving tool is powered down and secured before inserting or removing the bit. Tighten all set screws on Weldon-style holders fully before operation to prevent axial slippage. Wear appropriate PPE including eye protection whenever operating rotary drill equipment.