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Drill Bit Selection for Machining: Tips and Techniques
Properly selecting the right drill bit for your machining application is essential to ensure efficient operation, quality performance, and reliable results. No matter what parts you’re making or materials you’re working with, the right drill bit is the key to achieving optimal accuracy and precision.
This overview explores the considerations you should make when selecting a drill bit to help guide you in the selection process and equip you with tips that maximize productivity and minimize errors. Read on to learn all the tips and techniques you need to know about drill bit selection for machining.
Overview of Drill Bit Materials
One of the first considerations to make when choosing a drill bit is the material. There are different types of materials available, including high-speed steel, cobalt steel, and carbide. Each material functions slightly differently and delivers unique advantages for specific applications.
High-speed steel is a popular, accessible, and economical solution for most general maintenance applications. This drill bit material offers good heat resistance and wear resistance. It works best with relatively soft materials like softer steel, wood, and plastic.
Cobalt drill bits offer even greater durability and wear resistance than high-speed steel. Cobalt has excellent heat and corrosion resistance, making it a dependable and long-lasting tool material. Cobalt drill bits are ideal for working with stronger metals like stainless steel and other harder steel grades.
Carbide is a phenomenally strong material. It is resistant to wear and can stay sharp longer than other materials. Carbide drill bits are great for working with extremely hard and demanding materials. However, the hardness of carbide also makes it brittle, which means it can break easier than other drill bit materials. As a result, carbide drill bits require high-quality tool holders and equipment; you should never use a carbide drill bit with hand drills or drill presses.
Choosing the Appropriate Length of Drill Bit for Your Job
Choosing the proper length of drill bit for your job is important for both efficiency and safety. The right drill bit length allows you to make the most of your tools and complete your work without damaging the material or piece being worked on.
As a rule of thumb, try to choose the shortest drill bit that can complete the job. Shorter bits are more rigid, which makes them more accurate and less prone to breaking than longer alternatives. However, longer drill bits offer more reach for thicker materials or deeper cuts.
Stub, jobber, and taper lengths are among the most common drill bit lengths available. Stub-length bits, also known as screw machine length drill bits, are the shortest type of common drill bit. With a short length and flute, these bits are great for working in tight applications or creating straight, precise holes in harder materials.
Jobber-length bits are more versatile and provide the necessary reach for most jobs. Their medium length gives them decent durability and accuracy, making them a great choice for a wide range of applications.
Taper-length bits are longer than jobber bits, allowing them to cut deeper holes. This makes them ideal in special conditions, such as applications that require long cuts through thick material.
Flute Type
The flute is the sharp slot that spirals up the length of a drill bit and allows it to cut into materials. As such, the design of your bit’s flute affects your cut. Drill bits have two main flute types: standard and parabolic design.
Different materials require different flute types in order to produce the best results. Parabolic flutes allow for greater removal of chips when drilling through softer materials, such as aluminum. This helps create smoother holes at the end of your drill. However, straight flutes offer greater control over where the drill bit moves when drilling harder materials, such as stainless steel and titanium alloys. This helps maximize hole depth accuracy.
The Importance of Coating in Drill Bits
Having an appropriate coating will reduce friction when drilling and help keep the drill bit cool for extended use. Additionally, the right drill bit coating allows for more precise work since there is less resistance when cutting through materials. As such, protective coatings and finishes are a key part of drill bit selection for machining.
There are a few coating options available. A black oxide surface treatment adds an oily smoothness to the drill bit, decreasing friction and improving chip removal capabilities. Black oxide coatings also help resist oxidation and improve the durability of the drill bit.
Bright finishes are affordable coatings that add polish and durability to the bit while helping remove chips as you drill.
Titanium nitride is a bright gold, hard ceramic coating that reduces heat transfer and improves cutting ability against harder materials.
Titanium carbonitride is an extremely durable coating with a blue-gray color. It improves hardness, increases wear resistance, and allows for superior performance and cuts. The high lubricity of titanium carbonitride also helps reduce friction and improve efficiency while drilling.
Drill Bit Tip Styles
Drill bits are available in various tip styles that, while they may seem alike, greatly impact the kind of drilling you can do. The right drill bit tip helps prevent mishaps like walking or slipping, making it easier to create a clean cut and produce precise, high-quality results.
The biggest defining feature of different drill points is the tip angle. These angles usually range between 118 and 135 degrees.
Conventional drill points are the standard type of bit tip style. They usually have a tip angle of 118 degrees. This narrower point is great for soft metals like aluminum, milder steels, and non-ferrous metals. However, conventional drill points also have a 135-degree variant that is ideal for stainless steels and other harder materials. Conventional drill points are cost-effective and versatile. Moreover, you can easily resharpen these drill bit tips, making them a long-lasting tool with proper care.
Split point drill bits feature a more complicated drill point that helps eliminate slipping and walking while drilling. This results in improved penetration and an overall cleaner cut. Split point drill bits also come in both 118- and 135-degree point angles.
TMT Toolbox is your one-stop shop for drill bits and other metal cutting tools. Visit us today to explore our vast selection of metal-cutting metal drill bits and find the perfect tool for your next job.
