Chunk drill set

Drill Bit Set

If you are installing mortise locks, cabinet hinges, or creating clean, flat-bottomed holes in wood, standard twist drill bits will not deliver the precision you need. Our Professional Forstner Drill Bit Set, often called chunk bits by tradespeople, is the essential tool for achieving perfect results every time.

Forstner bits are unique in their ability to drill smooth, accurate, flat-bottomed holes with clean edges. They are the industry standard for installing mortise locks, where the lock case recesses into the door edge, and concealed cabinet hinges, which require a 35mm cup hole.

Unlike spade bits that can tear and splinter, Forstner bits create a precise, professional finish that is essential for fine woodworking and hardware installation.

Why Choose Forstner Bits for Door Hardware?

The defining feature of a Forstner bit is its ability to drill a perfectly flat-bottomed hole. This is critical when recessing the rectangular case of a mortise lock or the cylindrical cup of a concealed hinge into the door. A flat bottom ensures the hardware sits flush and square, guaranteeing proper operation.

Forstner bits feature a circular rim with sharp teeth that score the wood fibers before the cutting edges remove the material. This results in exceptionally clean holes with minimal tear-out, even in challenging grain patterns. The precision is far superior to spade bits or hole saws for this type of work.

One of the unique advantages of Forstner bits is their ability to drill overlapping holes. When creating a mortise for a lock, you can drill a series of overlapping holes to remove the bulk of the waste material quickly, then square up the corners with a chisel. This technique is far faster and more accurate than trying to drill a single rectangular hole.

Whether you are working with oak, pine, mahogany, or MDF, these bits are engineered to perform. The design allows for clean cutting across a wide range of materials, making them versatile for various projects.

The 7-Piece Professional Set

This carefully curated set provides the essential sizes for virtually all common door hardware installations and woodworking tasks. Each bit is crafted from high-quality materials for durability and precision.

The bit sizes included are 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, and 50mm.

The 35mm bit is the most critical size in the set. It is the standard size for drilling the cup hole for concealed cabinet hinges, often referred to as Malpha hinges or Malpha bits in some regions. Having this size ensures you can install modern kitchen and cabinet hinges with precision.

The 25mm and 30mm bits are useful for smaller hinges and preliminary drilling for lock cases. The 50mm bit is ideal for creating larger mortises for bulkier lock cases or for general woodworking projects requiring larger diameter holes.

Premium Construction

These bits feature carbide-tipped cutting edges. This offers superior hardness and wear resistance compared to standard high-speed steel bits. Carbide stays sharper longer, maintains its cutting geometry, and can handle abrasive materials like MDF without dulling quickly.

The 1/4 inch hex shank is a versatile and convenient feature. It has universal compatibility and fits all standard drill chucks, both keyed and keyless, as well as impact drivers with hex collets. The non-slip grip provided by the hexagonal shape prevents the bit from spinning in the chuck under heavy load, ensuring consistent power transmission. It allows for quick changes without fully opening and closing the chuck.

Each bit is precision-ground to exacting tolerances. This ensures concentric rotation with no wobble, which translates to accurate holes. It provides sharp cutting edges ready to use right out of the case. It guarantees consistent sizing so every bit drills true to its labeled diameter.

The set comes organized in a rugged, molded storage case. This protects the bits from damage, keeps them organized, and makes it easy to find the right size for the job. No more digging through a toolbox for the right bit.

How to Use Forstner Bits for Mortise Lock Installation

First, clearly mark the outline of the lock case on the door edge.

Second, set your drill depth stop to match the depth of the lock case. Consistency is critical.

Third, select a Forstner bit slightly smaller than the width of the mortise. Drill a series of overlapping holes within the marked area to the full depth. The flat bottom of the Forstner bit ensures each hole is the correct depth.

Fourth, the overlapping holes will leave some waste material. Use a sharp chisel to remove the remaining waste and square up the corners of the mortise.

Fifth, insert the lock case. It should sit flush and square. Trim with a chisel if necessary.

Technique for Concealed Hinge Cups

First, mark the center point for the hinge cup on the back of the cabinet door, using a template or measurements.

Second, ensure you are using the 35mm bit.

Third, set your drill depth stop to the manufacturer’s specified depth for the hinge cup, typically 12 to 13mm.

Fourth, drill slowly and steadily. The Forstner bit will create a perfectly clean, flat-bottomed hole with a precise circumference.

Fifth, the hinge cup should fit snugly and perfectly into the hole.

Tips for Optimal Performance

Forstner bits perform best at moderate to slow drill speeds. High speeds can cause overheating and burning, especially in hardwoods. For ultimate precision, especially on smaller pieces, a drill press is ideal. For door work, a handheld drill with a steady hand works perfectly.

Forstner bits can clog if chips are not cleared regularly. Withdraw the bit periodically to clear chips from the flutes. This prevents overheating and ensures a clean cut.

For hardwoods, a small amount of wax or cutting lubricant on the bit can reduce friction, prevent burning, and extend bit life.

Safety First

Always clamp your workpiece securely. The aggressive cutting action can grab the wood. Dull bits require more force and are more likely to grab or burn the wood. Always wear safety glasses when drilling.

Frequently Asked Questions

What is the difference between a Forstner bit and a spade bit?

A Forstner bit drills a clean, flat-bottomed hole with a smooth rim. It is guided by its outer rim and can drill overlapping holes. A spade bit has a pointed tip and flat blades. It drills faster but leaves a rougher hole, can splinter the wood, and does not create a flat bottom suitable for recessing hardware.

Can these bits be used in a cordless drill?

Yes, absolutely. The 1/4 inch hex shank is designed for easy use in standard cordless drills. For larger bits, a more powerful drill is recommended to maintain speed and torque.

Are these bits suitable for metal or plastic?

These Forstner bits are designed for wood, MDF, plywood, and some soft plastics. They are not suitable for drilling into metal, masonry, or ceramic. Using them on metal will instantly dull the carbide tips.

What does carbide-tipped mean?

It means the actual cutting edges are made of tungsten carbide, an extremely hard and durable material. Carbide-tipped bits stay sharp significantly longer than bits made entirely of high-speed steel. This is especially true when drilling abrasive materials like MDF or plywood.

Why is my Forstner bit burning the wood?

Burning is usually caused by drill speed being too high. Reduce your RPM. The bit may be dull. Check the cutting edges. Chips may not be clearing. Back out of the hole frequently to clear debris. Friction may be an issue. Apply wax or lubricant to the bit.

How do I sharpen a Forstner bit?

Sharpening Forstner bits requires specialized files or tools to maintain the precise geometry of the cutting edges. Many professionals prefer to replace dull bits rather than sharpen them, especially carbide-tipped ones, to ensure consistent performance.

The Professional’s Choice for Precision Drilling

Our 7-Piece Professional Forstner Drill Bit Set is the essential toolkit for anyone serious about installing door hardware or pursuing fine woodworking.

With the precise sizes needed for mortise locks and concealed hinges, durable carbide-tipped construction, and the convenience of a 1/4 inch hex shank, these bits will deliver perfect results project after project.

Invest in quality. Invest in precision. Choose the bits that professionals trust.

Chunk drill set   available in Mombasa, Kwale, Kilifi, Lamu, Mandera, Marsabit, Isiolo, Meru, Embu, Kitui, Machakos, Makueni, Nyandarua,

Nyeri, Kirinyaga, Murang’a, Kiambu, Turkana, Samburu, Trans Nzoia, Uasin, Gishu, Elgeyo Marakwet, Nandi, Baringo,

Laikipia, Nakuru, Narok, Kajiado, Kericho, Bomet, Kakamega, Vihiga, Bungoma, Busia, Siaya, Kisumu, Homa Bay, Migori, Kisii, Nyamira, Nairobi.

In Nairobi you can find them at: Westlands, Dagoretti,  Lang’ata, Starehe, Kamukunji, Embakasi, and Kasarani, Kibera, Mathare,

Eastleigh, Karen, Lavington, Westlands, Parklands, Runda, South C, South, Ngong Road

In Mombasa you can find us at : Nyali, Mwembe Tayari, Majengo, Likoni ,Bamburi, Miritini