Cylindrical cobalt drill bits set 8.5 mm, 5 pcs — GRAPHITE 57H048-5

Set of five cylindrical cobalt drill bits with an 8.5 mm diameter designed for drilling through hard metals and heat-resistant alloys. These GRAPHITE cobalt bits are manufactured from high-cobalt tool steel to provide superior wear resistance and maintain cutting edge hardness at elevated temperatures compared with conventional high-speed steel drills. The solid construction and straight shank make them compatible with hand drills and drill presses used in metalworking, maintenance and fabrication tasks.

Advantages

The cobalt composition increases hardness and thermal stability during high-speed drilling, reducing dulling and extending tool life. Precision ground flutes and cutting geometry improve chip evacuation and cutting efficiency when working with stainless steel, cast iron and other tough materials. The straight shank ensures secure clamping in standard chucks and improves concentricity for cleaner, more accurate holes.

Suitable for

• Drilling stainless steel and heat-treated steels
• Metal fabrication, workshop and industrial maintenance
• Repair work requiring durable drill bits for tough alloys
• Use in hand drills and bench drill presses

Key specifications

• Diameter: 8.5 mm
• Quantity: 5 pieces
• Material: high-cobalt tool steel (cobalt alloy)
• Shank type: straight cylindrical shank for standard chucks
• Tip style: ground for metal drilling

How to use

Secure the correct drill bit in the drill chuck ensuring it is firmly clamped and concentric. Mark the drilling position and, if necessary, use a center punch to prevent wandering. Use appropriate cutting speeds and feed rates for the workpiece material and apply cutting fluid when drilling stainless steel or hard alloys to reduce heat build-up and improve chip removal. Start drilling at a steady, controlled speed and moderate pressure; withdraw periodically to clear chips on deep holes.

Usage recommendations

For best results and longer bit life, select a lower speed and steady feed when drilling stainless or heat-treated steels, use a suitable cutting fluid, and avoid excessive dwell in the same spot to prevent overheating.