Drill bit Proline 77720 — metal, Ø 12 mm, length 375 mm, 1 pc

Proline 77720 is a single HSS metal drill bit with a 12 mm diameter and an overall length of 375 mm, designed for drilling through metal and other solid materials. The bit features a fully ground straight twist profile and a 135° point angle with chamfering adjustment to improve centring and reduce walking during start-up. Its extra-long design gives extended reach for deep holes and access to recessed or hard-to-reach workpieces, making it compatible with hand drills and drill presses for both workshop and on-site applications.

Advantages

The high-speed steel construction provides wear resistance and heat tolerance for metal cutting, while the fully ground flutes ensure accurate, straight holes and consistent chip evacuation. The 135° point angle with chamfering adjustment enables quick penetration and easier marking, reducing walking and improving hole quality. The extra-long length allows drilling of deep holes and access to confined areas without the need for extensions, and the single-piece packing makes selection and storage simple.

Suitable for

• Drilling through structural steel and metal fabrication tasks
• Workshop repairs and maintenance where long-reach holes are required
• Deep hole drilling in metal, non-ferrous metals and plastics
• Use with hand drills and drill presses for through-holes and guided drilling with bushes

Key specifications

• Material: high-speed steel (HSS)
• Diameter: 12 mm
• Overall length: 375 mm
• Point angle: 135° with chamfering adjustment
• Flute type: fully ground straight twist
• Intended materials: steel, non-ferrous metals, plastics
• Packaging: single-piece case

How to use

Secure the drill bit in the chuck of a hand drill or drill press ensuring proper concentricity and firm clamping. For best results when drilling metal, mark the drilling point and consider using a centre punch to prevent walking. Use appropriate cutting speed and feed for 12 mm HSS drills: moderate speed and steady pressure, with periodic withdrawal to clear chips on deep holes. Apply cutting fluid or lubricant when drilling steel to reduce heat and extend tool life. After use, clean chips from the flutes and store the bit in its case to protect the cutting edges.

Usage recommendations

For accurate guided drilling, use drill bushes or a drill press and low-to-moderate speeds with cutting fluid. When drilling deep holes, withdraw the bit regularly to remove chips and reapply lubricant to maintain cutting performance and prolong tool life.