Drill Bits 101: A Quick Guide for Maintenance Shops and Fabricators

Key Points:

• Choosing the right drill bit comes down to matching the drill point angle, material, and length to the specific demands of your application.

• Even a high-quality bit will fail if paired with the wrong material or run at incorrect speeds, making proper selection as important as the bit itself.

• Knowing the components of different drill bits and how they function in various applications helps you avoid mistakes and leads to better results.

Drill bits are one of the most commonly used tools in maintenance shops and fabrication environments. Whether drilling mounting holes, preparing surfaces for fasteners, or repairing equipment, choosing the right drill bit can improve efficiency and extend tool life. Choosing the wrong one can derail your project and add more time to your workday. 

This guide covers the most common drill types, materials, and features used in industrial maintenance and fabrication. By the end, you’ll know exactly which drill bit you need for specific job types.

Common Drill Point Types

A drill point is the cutting end of a drill bit that determines how it will cut the material. The two main drill point types are the 118° and the 135°. 

The 118° drill point is the most common style used in general drilling applications. It performs well in a wide range of materials, including mild steel, aluminum, wood, and plastics. Because of its versatility, the 118° point is often considered the standard general-purpose drill bit. 

The 118° drill bit is typically used for:

• General maintenance work

• Fabrication shops

• Light-duty drilling applications

The 135° split point drill has become extremely popular in industrial applications because it helps prevent the drill from walking—or shifting from its intended hole placement—when starting a hole. The split point gives this drill bit two additional edges and requires less force, making it especially useful for drilling harder materials such as stainless steel. It also produces smaller chips that are easier to clear than those from the 118° drill bit.

The 135° drill bit is best used for:

• High-alloy steels and stainless steel

• Industrial drilling environments

• Other heavy-duty, high-speed drilling applications

Used on mild steel, these drill bits can last for hundreds of holes. Hardened materials, such as those with a Rockwell C hardness over 30, will wear them faster.

Common Drill Bit Materials

Along with the different types of drill point angles, there are a few key types of drill bit materials that impact the hole you produce. Some of the most common materials include high-speed steel, cobalt, and tungsten carbide. 

High-Speed Steel

High-speed steel (HSS) drill bits are widely used in general-purpose drilling. HSS is heat-resistant and offers greater cutting speeds than carbon steel. Balancing durability and performance, these drill bits are best used on:

• Mild steel

• Hardwood

• Aluminum and other metals

• Plastic

Many maintenance departments rely on HSS drills because they can handle a wide range of everyday tasks. 

Cobalt

Cobalt drill bits contain an additional cobalt alloy that makes them more heat-resistant, helping them maintain their hardness at high temperatures. As a result, these drill bits are better suited for drilling harder materials like: 

• Stainless steel

• Hardened metals

• High-temperature drilling applications

Because of their durability, cobalt drill bits are often preferred in fabrication shops and production environments. One note to keep in mind is that cobalt is more brittle than HSS.

Tungsten Carbide 

Tungsten carbide is a compound made from equal parts of the metal tungsten and carbon atoms. Tungsten carbide drill bits are extremely hard and brittle, making them ideal for drilling tough, abrasive materials, including:

• Masonry and concrete

• Ceramic and tile

• Fiberglass

• Stone

• Copper, aluminum, and other metals

• Brass, bronze, and other alloys

Because of their hardness, carbide drill bits maintain a sharp edge much longer than HSS or cobalt, making them a popular choice in construction and specialty trades.

Common Drill Bit Lengths

Different drilling situations require different drill lengths. While those outside the industry may assume a longer length usually means more stable, precise drilling, experienced fabricators know this is not always the case. Here are some common lengths and the scenarios in which they are best utilized. 

• Jobber Length: Typically found in most standard toolboxes, the jobber length drill is the most widely used length for general drilling applications.

• Mechanic Length: Mechanic-length drills are slightly shorter than jobber-length drills, making them ideal for tight spaces and handheld drilling. 

• Screw Machine: Also known as stub-length, these drills are shorter and more rigid, making them stronger and better suited for machine drilling or situations requiring high rigidity and precision in tight spaces. 

How do you know which length you need? Choose the shortest drill bit that can comfortably reach the required depth. Shorter bits are more rigid, less likely to wander, and less prone to breaking.

Make sure the flute length (the spiraled part) is long enough to clear chips for the entire depth of the hole. Otherwise, you risk the bit seizing. If you must use an extended-length bit, use a lighter feed pressure to prevent bending and breakage. For deep, precise holes, start with a shorter, stubby bit to create a pilot hole, then switch to a longer bit if necessary.

Why Drill Bits Fail

Even the best drill bits eventually wear out and need to be replaced or sharpened. In addition to wear from repeated use, many failures result from improper drilling conditions. Some common causes include:

• Overheating: Excessive heat is the primary cause of bit death. Running drills at excessive speeds can cause the cutting point to burn, often leaving a bluish discoloration on the tip. 

• Catching in the Hole: Drills can chip or break if they catch while enlarging a hole or when chips build up during drilling. 

• Normal Wear: In most maintenance environments, drill bits are treated as consumable tools. When they become dull or damaged, they are typically replaced or sharpened.

Regular maintenance of drill bits ensures they continue to operate safely and efficiently. Carefully clean your drill bits after use and inspect them for safety hazards, such as chipped edges or warping. To avoid overheating, use cutting oil and a high-torque, low-speed setting for hard materials. 

Sharpening is also important for preventing drill bit failure, as dullness can lead to material damage. You can use freehand sharpening techniques or a drill grinding machine to restore the drill bit's ideal function. 

Choosing the Right Drill for the Job

The following drill-bit guidelines work well for most maintenance teams and fabrication shops. Make sure to keep a well-stocked drill index on hand so your team can quickly choose the right size and type of drill for the job. 

• For general drilling: Use HSS drills

• For harder metals: Use cobalt drills

• For improved hole starts: Use 135° split point drills

• For additional strength and stability: Use shorter drills

How Kelly Industrial Supply Supports Maintenance & Fabrication Professionals

For drill bits, fasteners, and a wide range of industrial components, Kelly Industrial Supply has your back. Our team supports maintenance departments, machine shops, and fabrication professionals with high-quality cutting tools, taps, and shop supplies designed for everyday industrial use.

Founded in 1991 as a small, family-owned industrial distribution company, Kelly Industrial Supply is the leading fastener distributor in West Chester, PA. Our mission is to help customers optimize the performance of their tools so they can focus on their projects, ensuring their success.

If your team is reviewing tooling inventory or replacing worn drill bits, let us help you keep operations running efficiently. To speak with a team member, contact us online or call 610-429-8266 today.

FAQs 

Can I use the same drill bit for both wood and metal?

While some drill bits are versatile enough to handle both wood and softer metals like aluminum, using a single bit across very different materials may accelerate wear and reduce precision over time. For best results, it’s worth keeping separate bits designated for each material type.

How do I know when it's time to replace a drill bit rather than sharpen it?

If a drill bit shows visible chipping, warping, or a burned tip with bluish discoloration, sharpening alone may not restore safe performance. Other signs of irreversible wear include bits that require significantly more pressure than usual to cut or that repeatedly move off-mark when drilling. Keep a well-stocked drill index so your team never has to push a compromised bit further than it should go.

Does drill speed matter as much as the bit type when working with hard metals?

Yes, both are important. Harder materials, such as stainless steel and high-alloy steels, generally require slower speeds to manage heat buildup, which is one of the leading causes of premature bit failure. Pairing the correct bit material with an appropriate speed setting is the best way to extend tool life and improve hole quality.

Is a 135° split point drill bit always the better choice over a 118°?

Not necessarily. The 135° split point excels in harder materials and high-speed production environments where preventing drill walk is critical, but it can be overkill for everyday light-duty tasks on softer materials. The 118° point remains a reliable, cost-effective option for general maintenance work where extreme precision on hard surfaces isn’t the priority.