What are the main types of drill bits for metal, and when should I use each?

High-speed steel (HSS) bits are a common choice for general-purpose drilling in metal, wood, and plastic, offering a good balance of cost and performance. Cobalt drill bits are more heat-resistant, making them suitable for harder metals like stainless steel. For very hard materials or production drilling, carbide-tipped bits provide excellent durability and cutting speed. When selecting, consider the material hardness and desired hole precision.

What's the difference between jobber length and other drill bit lengths?

Jobber length drill bits, like the Hanson HSS series, are a standard, general-purpose length. They offer a good compromise between reach and rigidity. Shorter bits, such as screw machine length, are more rigid and reduce the risk of breakage, while longer bits, like extension or aircraft length, allow you to drill deeper holes. Choose the length based on the depth and accessibility of the hole you need to drill.

What are masonry drill bits and how do they differ from standard drill bits?

Masonry drill bits, such as the Vermont American Double Flute Masonry Bit, are designed for drilling into brick, concrete, stone, and other masonry materials. They typically feature a carbide tip that is much harder than standard steel bits, allowing them to withstand the abrasive nature of masonry. Also, they often have a double flute design to remove debris more efficiently. Standard drill bits are not suitable for masonry as they will quickly dull or break.

What is a step drill bit (Unibit) used for?

A step drill bit, sometimes called a Unibit, is designed to drill multiple hole sizes with a single bit. They are ideal for drilling clean, round holes in thin materials like sheet metal, plastic, and wood. The stepped design allows you to gradually increase the hole size, reducing the risk of snagging or damaging the material. Always use cutting oil when drilling metal with a step drill bit to prolong its life and improve the quality of the hole.

How do I choose the right size drill bit for tapping threads?

Selecting the correct drill bit size for tapping threads is crucial for creating strong, accurate threads. The drill bit size depends on the tap size and thread pitch. Use a tap drill chart to determine the correct drill bit size for your specific tap. It's generally better to err on the side of a slightly larger drill bit to avoid breaking the tap, especially when working with harder materials.

What is the significance of the point angle on a drill bit?

The point angle of a drill bit affects its performance and suitability for different materials. A 118-degree point angle, common on general-purpose HSS bits, is suitable for drilling steel, wood, and plastic. A sharper angle, like 135 degrees, is better for drilling harder materials like stainless steel and helps prevent the bit from wandering. Always verify the point angle is appropriate for the material you are drilling.

What can cause a drill bit to break, and how can I prevent it?

Drill bits can break due to a variety of factors, including using the wrong type of bit for the material, applying excessive pressure, overheating, or wobbling due to an improperly secured workpiece. To prevent breakage, use the correct type of drill bit for the material, apply steady and moderate pressure, use cutting fluid to reduce heat, and ensure the workpiece is securely clamped. Also, inspect your bits regularly for wear or damage.

What safety precautions should I take when using drill bits?

Always wear appropriate personal protective equipment (PPE) when using drill bits, including safety glasses to protect your eyes from flying debris. Secure the workpiece firmly to prevent it from spinning or moving. Avoid wearing loose clothing or jewelry that could get caught in the drill. If drilling metal, be aware that the bit and workpiece can become hot, so use caution and wear gloves if necessary. Always consult the tool and accessory's safety guidelines.