Irwin 5/16″ x 3-3/4″ Left Cobalt HSS Fractional Drill Bit (31520)

Description

Irwin 5/16″ x 3-3/4″ Left Cobalt HSS Fractional Drill Bit (31520) is engineered with a unique left-hand cutting direction, making it the perfect solution for removing broken fasteners such as screws, studs, and bolts. Instead of tightening the fastener as a standard drill bit would, the left-hand spiral rotates counter-clockwise, effectively gripping and loosening the broken piece as it drills. This often allows for the complete removal of the fastener without the need for an additional extractor. Constructed from M42 High-Speed Steel with 8% cobalt, this bit is built to withstand the high temperatures and friction associated with drilling into hard materials like high-alloy steel, cast iron, and stainless steel. The 135° split point tip ensures a precise, clean start and prevents the bit from “walking” on the surface, while the gold oxide finish provides added lubricity and heat resistance. This combination of features makes the Irwin 31520 a reliable and efficient tool for demanding drilling applications.

KEY FEATURES AND BENEFITS:

• Left-Hand Cutting Direction: This is the primary feature of this drill bit. It rotates counter-clockwise, which is essential for removing broken fasteners as it applies force to loosen the broken part rather than tightening it.
• M42 Cobalt High-Speed Steel: The 8% cobalt content in the steel alloy provides significant heat resistance and hardness, allowing the bit to maintain its cutting edge and structural integrity when drilling through tough, abrasive materials.
• 135° Split Point: The split point design eliminates the need for a pilot hole or center punch, as it starts drilling on contact. This feature minimizes “bit walk” and provides a clean, accurate hole from the very beginning.
• Gold Oxide Finish: The gold oxide coating serves to reduce friction and heat buildup during drilling. This extends the life of the drill bit and improves its performance in demanding applications.

SPECIFICATIONS:

• Product ID: 31520
• Brand: Irwin
• Material: M42 High-Speed Steel with 8% Cobalt
• Diameter: 5/16″
• Overall Length: 3-3/4″
• Flute Length: 2-1/8″
• Cutting Direction: Left Hand
• Point Angle: 135°
• Shank Style: Straight
• Finish: Gold Oxide

HOW TO USE:

1. Prepare the Workpiece: Ensure the workpiece is securely clamped to prevent movement. If drilling a broken fastener, ensure the surface is as flat as possible.
2. Select the Right Speed: Left-hand drill bits generally require a slower drilling speed than standard bits, especially when working with hard metals. Refer to a drilling speed chart for the specific material you are working with.
3. Insert the Bit: Securely insert the straight shank of the Irwin 31520 drill bit into your drill chuck.
4. Start Drilling: Begin drilling into the broken fastener with a slow, steady, and even pressure. Do not apply excessive force, as the bit’s design will allow it to bite into the material effectively.
5. Observe the Action: As the bit drills, its left-hand rotation will be working to unscrew the broken fastener. If the fastener begins to turn, continue to drill until it is fully backed out.
6. Use with an Extractor (if needed): If the bit drills into the fastener without removing it, the resulting hole is the perfect starting point for a screw extractor.

BENEFITS OF USING IRWIN 5/16″ X 3-3/4″ LEFT COBALT HSS FRACTIONAL DRILL BIT (31520):

• Saves Time and Effort: This bit can often remove broken fasteners on its own, eliminating the need for a separate extraction tool and saving time on the job.
• Extends Tool Life: The M42 cobalt material and gold oxide finish significantly increase the bit’s lifespan, especially when used on tough materials that would quickly dull or break a standard bit.
• Improves Accuracy: The 135° split point minimizes bit wander, ensuring that you drill precisely where you intend to, which is critical when working on delicate components or tight spaces.
• Versatile in Hard Materials: Engineered for drilling into high-alloy steels, stainless steel, and other difficult metals, this bit is a valuable addition to any professional’s toolkit.

FEATURES:

• Made from M42 high-speed steel with 8% cobalt for maximum performance.
• Designed with a left-hand spiral for counter-clockwise rotation.
• Features a 135-degree split point for self-centering.
• Gold oxide surface finish for reduced friction and heat.
• Short “mechanics length” design for enhanced rigidity.
• Straight shank compatible with standard chucks.
• Flute geometry optimized for efficient chip evacuation.
• Specifically engineered for drilling into hard and abrasive materials.