Stub drills, also known as stub-length drills, are shorter and more rigid versions of standard jobber drills, designed specifically for applications where stability, accuracy, and reduced deflection are critical. The reduced length of the stub drill minimizes wobbling and increases its strength, making it ideal for use in tight spaces or in situations where high precision is required. These drills typically have a flute length that is about 2 to 4 times the diameter of the bit, much shorter than the length of jobber drills. The shorter length also means that stub drills are less prone to bending, ensuring straight and accurate holes, even when drilling into harder materials like metal.

Stub drills are frequently used in situations that demand tight tolerances and consistent results, such as in aerospace, automotive, and precision machining industries. They excel in operations like drilling shallow holes, pre-drilling for tapping threads, and making spot drill holes that will later guide other drilling tools. The rigidity of stub drills ensures that the tool won’t deflect or walk off the mark, which is essential for maintaining accuracy during high-speed drilling or when working with materials that are particularly difficult to drill.

The material composition of stub drills is typically high-speed steel (HSS), but they are also available in more durable versions made from cobalt or with coatings like titanium nitride (TiN), which enhances wear resistance and heat dissipation. These materials enable the stub drill to withstand the friction and heat generated during demanding drilling tasks, especially when working with metals such as stainless steel, cast iron, or harder alloys. Additionally, the shorter flute length makes chip evacuation more efficient, reducing the risk of clogging and overheating.

The point angle on a stub drill is often 135 degrees, which is sharper than the standard 118-degree angle found on jobber drills. This sharper angle is ideal for harder materials, providing a more aggressive cutting action and reducing the amount of thrust required to initiate the cut. The design also helps prevent the drill from skating across the surface, especially when no pilot hole is used. Stub drills can also be used in high-speed production environments where repeated drilling tasks are performed, as their robust design allows them to maintain precision over longer periods of use without breaking or dulling.

In terms of versatility, while stub drills are particularly suited for metalworking, they are also used in other fields such as woodworking, plastic manufacturing, and electronics assembly. Their compact size makes them easy to handle, and they fit well in machine setups where longer drills might pose a clearance issue. Whether for drilling accurate pilot holes, pre-drilling for screws, or working in tight spaces, stub drills are indispensable tools for machinists and engineers who require precision, durability, and reliability in their drilling operations.