Twist drill bit set Irwin 4 mm, 10 pcs, model 10502520

Irwin twist drill bit set 4 mm, 10 pcs, model 10502520 contains ten identical HSS cobalt 4 mm twist drill bits intended for general and heavy-duty metal drilling. Each bit is manufactured to DIN 338 standards and incorporates 5% cobalt for improved heat and abrasion resistance. The 135° split point geometry reduces bit walking and enables faster penetration into metal surfaces, while a heavy-duty web construction increases strength and durability for repetitive workshop, construction and maintenance tasks.

Advantages

The set delivers consistent performance across multiple identical 4 mm bits, allowing rapid replacement during production or repair work. HSS cobalt composition (5% cobalt) enhances wear resistance and maintains hardness at elevated temperatures, making the bits better suited to drilling hard or heat-treated metals than standard high-speed steel. The 135° split point starts cutting immediately, reducing the need for center-punching in many applications, and the robust web reduces breakage risk during heavy-duty use.

Suitable for

• Drilling into steel and other hard metals, including heat-treated and abrasive alloys
• Workshop and maintenance drilling tasks requiring multiple spare bits
• Construction and mechanical assembly where repeatable hole quality is needed
• Portable and bench drilling operations with power drills and drill presses

Key specifications

• Drill bit type: Twist drill bits (HSS cobalt)
• Material composition: High-speed steel with 5% cobalt
• Diameter: 4 mm
• Quantity: 10 identical pieces
• Point angle and geometry: 135° split point for reduced walking
• Standards: Manufactured to DIN 338
• Construction: Heavy-duty web for increased strength
• Primary application: Metal drilling, including hardened and abrasive alloys

How to use

Select a compatible drill or drill press with appropriate chuck capacity and secure the workpiece. Mark the drilling location and, if required for precise alignment, use a center punch to create a small dimple. Install a 4 mm bit from the set into the drill chuck and tighten securely. Begin drilling at low speed to establish the hole, then increase speed as appropriate for the material and machine. Apply steady pressure and periodic coolant or cutting fluid when drilling hard or heat-treated metals to extend bit life and reduce heat buildup. Withdraw the bit occasionally to clear chips and avoid clogging.

Usage recommendations

For best results when drilling hardened or abrasive metals, use cutting fluid and moderate feed pressure, maintain correct drilling speed for 4 mm HSS cobalt bits, and replace bits from the set as they become worn to keep hole size and finish consistent.