Drill bit GRAPHITE 57H026 cobalt for metal cylindrical tip 4.2 mm

GRAPHITE 57H026 cobalt drill bit for metal, 4.2 mm cylindrical tip, is designed for drilling hardened and stainless steels as well as other ferrous and non-ferrous metals. The cobalt-enriched high-speed steel composition improves heat resistance and extends tool life under continuous cutting loads. The cylindrical tip geometry provides precise centering and consistent chip evacuation when used with hand drills and drill presses in workshop or light industrial environments.

Advantages

The cobalt alloy increases hardness at elevated temperatures, reducing wear during drilling of tough metals. The 4.2 mm diameter and cylindrical tip permit accurate hole positioning and predictable hole size, while the robust shank ensures steady clamping in standard drill chucks. This drill bit is suitable for repeated use on hardened materials where ordinary high-speed steel bits would lose cutting performance more quickly.

Suitable for

• Drilling hardened steels and stainless steel
• Metal fabrication, repair and modification tasks
• Workshop use with hand-held drills and drill presses
• Pilot holes and precision metalworking where a 4.2 mm hole is required

When it may not be suitable

This cobalt drill bit is not intended for prolonged use on masonry, concrete, or wood; such materials require dedicated masonry or wood bits. For very soft metals or non-metal materials where extreme hardness is unnecessary, a standard high-speed steel bit may offer adequate performance at lower cost. Extremely high-volume automatic production may require specialized carbide tooling for maximum lifetime and cycle speed.

Key specifications

• Material: cobalt-enriched high-speed steel
• Tip type: cylindrical (straight) tip
• Diameter: 4.2 mm
• Intended materials: hardened steel, stainless steel, other metals
• Shaft type: straight shank for standard chucks

How to use

Select an appropriate drilling speed and apply steady feed pressure; lower speeds are recommended when drilling stainless or hardened steel to reduce heat build-up. Use cutting fluid or coolant to improve chip evacuation and extend tool life. Secure the workpiece firmly in a vice or fixture and ensure the drill bit is properly centered before starting. Withdraw the bit periodically to clear chips when drilling deeper holes.

What to consider before purchase

• Confirm 4.2 mm diameter suits your hole requirements and any fastener or pilot specifications
• Ensure your drill or drill press can run at speeds appropriate for cobalt HSS bits and accepts a straight shank
• Consider whether cobalt-enhanced bits are necessary for your material, or if standard HSS or carbide would be more cost-effective

Usage recommendations

Use cutting fluid and moderate speeds when drilling stainless or hardened steels, clamp the workpiece securely, and avoid excessive side loads to maximize the service life of the 4.2 mm cobalt drill bit.