How To Choose the Right Broaching Tool for Your Application
Broaching is a metal cutting technique that allows manufacturers to create unusually shaped cuts quickly and easily. The process uses specialized metal cutting tools known as broaches. Because broaching involves creating unique cuts with a single stroke, metalworkers need their broaches to be precise and efficient. That’s why learning how to choose the right broaching tool for your application is so imperative.
With a thorough understanding of how broaches and broaching machines work, you can find the right tools for the job and create a clean, precise, and efficient cut every time. Implement a successful broaching workflow into your machine shop with this guide on everything you need to know about broaching and broaching tools.
What Is Broaching?
Many metal cutting processes involve straightforward cuts and shapes like straight lines or simple holes. But when you need a more complex cut, broaching might be the way to go. Broaches are thin bars with teeth that grow larger and larger down the length of the tool. With broaching, metalworkers can make irregular holes or surface cuts in shapes such as squares, hexes, or keyholes.
These types of cuts would be extremely difficult or expensive to produce without specialized broaching tools. However, the right broach can make these cuts quickly and smoothly. Metalworkers don’t even need to sand or finish the product after using a broach. As a result, broaching is an ideal process for pieces that require extreme precision or massive output.
How Do Broaches Work?
How do broaches achieve such great efficiency and precision? The answer lies in the tool’s design. The teeth along the bar of the broach work to remove metal from the workpiece as it cuts. Because the teeth grow progressively larger, each tooth removes slightly more material until the end of the broach, which is the exact shape of the cut the worker wants to make.
This allows the broach to act as its own finishing tool, with each progressive set of teeth making more and more precise cuts until you have a smooth, accurate, and complete cut. Moreover, the teeth work to carry away metal chips as they go, which helps the broach move efficiently and leaves a clean and smooth cut at the end of the broaching process.
Different Types of Broaches
As with many metal cutting tools, broaches come in a wide range of styles and options to suit different needs. A few common broach categories include round, spline, helical spline, standard keyway, and specialty broaches. However, there are still endless variations within these categories to help metalworkers find the right tool for their precise needs.
Round broaches are the most common and straightforward type of broaching tool. As the name implies, a round broach makes a round hole in the workpiece, similar to a drill press. However, round broaches tend to be faster and cleaner than drill presses and other metal cutting tools. Round broaches can also achieve a tighter tolerance. Round broaches are ideal for cutting holes quickly and accurately in high-volume projects that require mass production.
Spline broaches cut ridges, teeth, or notches into the perimeter of a pre-cut hole. This creates splines, which are invaluable designs in pieces like driveshafts, transmissions, and other automotive parts. The spline broach cuts evenly spaced ridges into the workpiece, allowing it to fit precisely with a mating piece and transfer torque without slipping or coming loose.
Helical Spline Broaches
Helical splines also create an evenly spaced set of notches into the interior of a pre-cut hole, but these ridges create a spiral shape instead of following a straight line. This design requires even greater precision than standard spline broaches, which is why helical spline broaches are so instrumental to the process. Helical splines are useful for manufacturing automotive parts, firearms, and other precise equipment.
Standard Keyway Broaches
One of the most common uses for broaches is cutting keyholes. These projects come in many different styles with countless potential requirements. Metalworkers might need to make a key-shaped hole in a workpiece, or they might need to cut notches into the perimeter of another hole to insert a key. While some keyhole projects require custom tools, a standard keyway broach is a good starting point for most keyhole cuts.
When a stock broach won’t fit your project, a specialty broach might be the best option. These are custom broaches that metalworkers can design and order to fit a specific shape or cut. Designing and using your own specialty broach is a great way to quickly and accurately produce a high volume of specific parts with as little cost or hassle as possible.
Different Broaching Machines
Broaches only make up one part of the broaching process. When learning how to choose the right broaching tool for your application, it’s also important to learn about the different types of broaching machines. Broaching machines work by either guiding the broach through the workpiece or guiding the workpiece through the broach. However, the most important role of a broaching machine is to position the broach and the workpiece precisely. This allows metalworkers to create a highly accurate cut for extremely precise parts. There are four main types of broaching machines: vertical, horizontal, surface, and rotary.
Vertical Broaching Machine
Vertical machines work by either pushing or pulling the broach vertically across the workpiece. These broaching options have a smaller footprint and work well with smaller projects that use short or lightweight broaches.
Horizontal Broaching Machine
Horizontal broaching machines only use pull broaching. The workpiece remains in place while the machine pulls the broach through the piece. Pull broaching is ideal for higher-volume applications. As such, horizontal broaching machines are best for operations that require more space or a greater power output.
Surface Broaching Machines
Unlike vertical and horizontal machines, which are ideal for internal cuts, surface broaching machines focus on creating exterior cuts along an outside edge of a workpiece. For example, say you need to cut grooves into the outer edge of a metal disc. A surface broaching machine can push the broach horizontally or vertically along the edge of the disc to make those cuts.
Rotary Broaching Machines
Rotary broaching machines come in two main variants: rotary continuous broaching and horizontal continuous broaching. Rotary continuous broaching machines use a rotating table to move the workpiece beneath a fixed broach in a circular motion. Horizontal continuous broaching machines have a chain that moves continuously through the workspace. Metalworkers fix the workpiece to the chain, which moves beneath a fixed broach in a straight line.
Finding the Right Cutting Tools at TMT Toolbox
Finding the right precision metal cutting tool for your project is key to creating a clean, accurate cut. Save time and materials when you visit TMT Toolbox—shop our vast range of metal cutting tools and other essential workshop equipment today.