Forstnerbor

Forstner bit, or Forstnerbohrer, is a woodworking drill bit designed to bore clean, flat-bottomed holes with minimal tear-out. It features a central guide point and a cylindrical body with a circular cutting rim and two or more cutting lips. The combination allows the bit to drill precise holes without wandering, making it popular for bored hinges, dowel holes, and large diameter recesses.

Operation and design details: The center point helps align the bit on the mark, while the sharp rims shear the wood around the edge. The flat bottom created by the cutting edges produces a smooth floor suitable for dowels or sockets. Forstner bits are commonly used with drill presses for accuracy, though they can be used in handheld drills if steadiness and slow speeds are maintained.

Applications and advantages: They excel at producing clean, flat-bottom holes in hardwoods and softwoods alike. Their ability to drill near the edge of a workpiece and to create overlapping holes makes them ideal for drilling blind holes for dowels, hinge mortises, or recessing areas for hardware. Compared with twist bits, Forstner bits typically deliver crisper edges and a more uniform bottom.

Sizes and materials: Forstner bits come in a wide range of diameters, commonly from about 6 mm to 60 mm or more. Common shanks are straight, compatible with drill chucks. They are usually made from high-speed steel (HSS); higher-end variants may be carbide-tipped or feature hardened rims for longer life.

Maintenance and tips: Keep bits sharp for best results and avoid overheating by drilling gradually and clearing chips frequently. Sharpening is delicate and often best handled by professional resharpening service for precise edges. Always back up the workpiece when drilling deep holes to prevent tear-out.