How to Choose the Right Drill Bit for Your Application

How to Choose the Right Drill Bit for Your Application

Drill bits. One of the most useful and versatile tools that exist. You may be surprised to know that using the wrong one can not only hinder production, but could be costing more than you may think. That’s why it’s important to choose drill bits that are optimized for the application. Otherwise, you’re likely to be replacing the bits and the tools too often. Not only that, but you risk damaging the workpiece and having to start over.

Machinists and fabricators use drills daily, and proper drill bit selection can save both time and money. If you are looking to get the best machining result, here are some things to consider when choosing a drill bit for your next project.

Choosing the Right Drill Bit for the Job

Morse Cutting Tools – HSS

There are countless drill bits on the market today, making selection both difficult and time consuming. Two main categories of drill bits include standard bits used with handheld drills or drill presses and boring machine bits that are used in automated machinery like drill banks and CNC machines. Here are some brief explanations of various types of drill bits.

Twist Drill bits are the most common and can be used in a variety of everyday tasks from drilling woods, metal and plastic. They are made from High-Speed Steel or Carbon Steel.

Counterbore bits create a flat bottom blind hole with a smaller diameter center hole. These are often used to create a recess that can hide a fastener head.

Countersink bits create a tapered surface hole with a smaller center hole to allow fastener to sit flush with the material.

Flat Bottom Boring bits are similar to counterbores, but do not have a center drill.

Specialty bits are essentially all bits that don’t fit into the above categories and can be used with glass, tile or other specialty materials.

Coolant Through Drills have coolant ports that run through the drill and feed coolant to the cutting edge, allowing for faster cutting and improved chip evacuation. Used in high performance drilling operations.

Exchangeable Tip Drills have replaceable carbide heads or tips that saves time when changing tools and saves money over larger solid carbide drills. They also boost productivity in many machining applications.

Spade Drills have spade inserts that allow for cost effective drilling of deep holes and large diameter holes. They also run well on older machines and at lower speeds than high performance carbide drills.

Inserted Drills have multiple carbide inserts that handle the metal cutting. They are faster than HSS and cobalt drills, are cost effective and many can be used to “turn” the hole to a larger diameter than the drill size, much like using a boring bar in a lathe.

Understanding Drill Bit Materials

Drillco Drills

Certain tooling and machining operations require specialized drill bits that allow for effective drilling, without burning out too quickly.  Below, you’ll find some common drill bit materials and their uses.

Cobalt (HSCO): Despite being more brittle than HSS, cobalt drill bits are ideal for drilling harder steel as well as stainless steel grades. They are often more expensive than other drill bits but tend to last longer.

Carbide (Carb): Carbide is considered the hardest and most brittle drill bit material and can cut hardened steel, stainless steel and aluminum with ease. Ask if the CoroDrill 860 from Sandvik Coromant is right for you.

Diamond: These bits are effective for drilling tile, stone or other hard material and the use of water is recommended to prevent damage to the workpiece or tool. These are costly, so they are recommended for use in very specific tasks.

High-Speed Steel (HSS): High-Speed Steel bits are harder, more resistant to heat and can drill metal at greater cutting speeds than high-carbon steel. Ask about our HSS drills from Morse or Drillco that are available in a variety of lengths, including jobber and stub/screw.  

How Flute Design Impacts Cut

Flutes are grooves that are cut into the body of the drill bits to provide cutting surfaces, permit removal of chips and allow cutting fluids to reach cutting surfaces. There are different variations of flutes, but here are some common ones you should know.

Standard: Standard flutes are the most common and have a circular cross section.

Parabolic Design: This refers to the open geometry and faster spiral of a twist drill bit. It offers improved chip evacuation, increased feed rate, shorter cycle times and reduces the need for a peck cycle. It’s also less likely to jam and break.

Straight Flute: Used when drill rigidity is more important than chip evacuation, especially in short chipping materials. Also, can be used when the workpiece is spinning instead of the drill itself.

Source: CNC Cookbook

Drill Point Coatings Explained

Coatings reduce friction when drilling. That reduction of heat helps to protect the drill bit and improves the flow of material out of the hole. See below for a brief explanation of various drill point coatings.

Black Oxide is a black surface coating that improves heat resistance, reduces friction and increases chip flow.

Bronze Oxide coatings help to increase tempering and relieves stress on the bit.

Bright drill points do not have a coating, but they are polished for increased chip flow and can be used in plastics, woods and aluminum.

Titanium Nitride (TiN) coatings help drills run faster and increases tool life because it increases the hardness of the bit. Look for drill points to be gold in color.

Titanium Carbonitride (TiCN) is ideal for stainless steel, cast iron and aluminum as it is harder and more wear-resistant than other coatings. Look for drill points to be a blue-gray in color.

Titanium Aluminum Nitride (TiALN) is ideal for use in high-alloy carbon steels, nickel-based materials and titanium, but should not be used for drilling aluminum. Look for drill point color to be violet.

“Man must shape his tools lest they shape him.”

Choosing the wrong tools can impact your productivity and profitability. With so many options out there, choosing the right cutting tools can be overwhelming — but it doesn’t have to be. We take pride in the level of knowledge and experience the M&M Sales & Equipment team has to offer our customers.

If you’re looking to improve production in your facility, but don’t know where to start, give us a call or stop in at one of our four locations. We offer a variety of quality drills from top-rated brands like Drillco, Morse, Guhring and Sandvik Coromant. Whatever your production needs are, M&M Sales & Equipment can help you get it done. Contact us today.

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