Comprehensive Guide to Broaching Tools

A broach is a tool used to cut those seemingly impossible holes in metal, such as squares, double-D, hex, keyholes and more. In its purest form, a broach is a slender bar with increasingly large teeth size placed along its length. 


It can grow far more complicated than that, however. Broaching is used in many areas of machining, and in some instances can provide cuts that are either next to impossible or prohibitively expensive through other means — it is also extremely efficient. Most broaching is done in a single stroke, leaving a smooth finished product that doesn't require sanding.

Broaching is favored when cuts are odd-shaped or when you need to produce large quantities of a product. These tools work extremely quickly and are capable of massive outputs. Broaching also allows for extreme precision. When a part needs to be machined within several millionths of an inch, broaching can provide such tolerances while also maintaining a rapid production rate. 

How Broaches Work

Most machine work involves rotating blades, grinders, drills and other cutting implements. The work of these devices is accompanied by flying sparks and a shower of metal filings, and each one also takes time and a considerable amount of finishing to become a completed product. Items often must be deburred, touched up and polished. 

A broach operates in a much more efficient way. The broach itself is usually nothing more than a thin rod, and this rod is plunged through the workpiece, so the hole takes the shape of the rod's exterior. There are no sparks, no tiny metal projectiles and no strenuous, long cuts required. Often, broaching a piece takes a matter of seconds instead of minutes.

The design of the broach itself is responsible for the efficiency of this process. A typical type of linear broach uses a metal bar to form a shape in the workpiece. Along the bar are teeth for removing metal from the object. Each tooth is progressively larger than the last so each tooth will remove slightly more material as the broach passes through the workpiece. The final tooth is the exact shape and form of the desired cut.

The first set of teeth on a broach are designed to make a rough cut, removing material in larger quantities than the last teeth. The next set of teeth then make more precise cuts, performing a semi-finishing job. The final teeth make the sharpest cuts of all, which leaves the object smooth and accurate. Additionally, the broach has carried all the metal shavings away from the item, so there is little cleanup to be done.

Broaches have a higher upfront cost than other parts of their size in the machining world, but they can have extremely long lifetimes with proper sharpening. Colonial Tool offers sharpening services that can multiply the lifespan of your broach many times over. 

Different Types of Broaching Machines

The broaching machine is responsible for moving the broach through the workpiece or the workpiece through the broach — it does this either by pushing or pulling. It also is responsible for maintaining the position of the workpiece to ensure accuracy. This machine comes in several different forms, including:

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  • Vertical Broaching Machines: These machines push or pull the broach in a vertical direction. They take up less room on the floor than horizontal broaching machines and are typically used for surface broaching operations. Most operators choose hydraulic power for their vertical broaching machines, as this is less expensive. Vertical broaching machines are best for applications where the broach is not unusually long or heavy.

  • Horizontal Broaching Machines: This category of broaching machine consists entirely of pull-type operations. Pull-type operations are those in which the broach is first pushed through the workpiece. Then, as soon as it emerges from the other side, a hook latches through the pilot and pulls it the rest of the way through. These machines take up more room due to their horizontal configuration — however, they also have sufficient power to operate on heavy objects. They are useful for round, spline, slot or keyway broaching, as well as an assortment of other internal outlines.

  • Surface Broaching Machines: Whereas vertical and horizontal broaching machines are excellent for internal cuts, a surface broaching machine specializes in cuts along one edge of a piece. For example, if a metal disc needs a notch cut out of its edge, it is fixed in place on a surface broaching machine. The broach slides in a vertical or horizontal guided track alongside it, and the teeth will notch out the appropriate cut in the side of the disc. The part that pushes the broach is called a ram.

  • Rotary Continuous Broaching Machines: This machine places the workpiece on a rotating table. Above the table is a broach attached to a broach holder, which remains stationary while the table and workpiece rotate below. As the table turns, the piece comes in contact with the broach, removing material in a circular path.

  • Horizontal Continuous Broaching Machines: Also referred to as "chain" broaching machines, these devices mount the workpiece on a continuously revolving chain. This type of machine excels at high volume jobs. However, due to the movement of the chain, it cannot deliver as precise tolerances as some of the other broaching methods.

Different Types of Broaches

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Broaches themselves come in an endless variety of shapes and sizes, as broaching is an extremely versatile operation. However, some of the most common mainstays include:

  • Round Broaches: The simplest type of broach is a circular broach. This is a round bar that produces a hole similar to one made by a drill press. The difference lies in the fact that a broach cut is quicker, cleaner and can achieve a tighter tolerance. Round broaches can be used to produce accurate holes rapidly and are great for high-volume mass production.

  • Spline Broaches: Spline broaches allow operators to cut a sequence of teeth or notches around the perimeter of a hole that has already been cut. This particular shape is of extreme importance in the automotive industry, where splines play a considerable role in driveshafts, transmissions and other parts. The ridges along the circumference of the spline create an efficient means of conveying power from one section to another, as the part that fits inside it will not have any wiggle room. Broaching ensures the accuracy required by these high-tech components can be accomplished.

  • Speciality Broaches: The beauty of broaches is that they can be made to create many different types of holes and cuts. Whether you need a particular kind of shape or something more complicated, a specialty broach can be made to fit your needs. Colonial Tools is a leader in crafting high-quality specialty broaches and can provide you with a free quote for your project. Some typical examples are concave broaches — which are used to create seat sectors — turbine discs and blades.

  • Standard Keyway Broaches: Creating keyways is a matter of precision, and stock parts don't always offer it sufficiently. A keyway can take many forms, from a key-shaped hole to a notch in the perimeter of another hole, which is used as a point for a key to rest in the part.

  • Helical Spline Broaches: These broaches create a spiral set of grooves on the interior wall of a hole due to the configuration of their teeth, which must be extremely precise in their placement to ensure a proper cut. This type of broach is a big player in manufacturing firearms and automobile transmissions. Despite the stringent requirements for accuracy, a well-made helical spine broach can be used to create a large number of replicated parts quickly.

What Kind of Broach Do I Need?

The areas of industry where broaching plays a role are ever-growing. If you are looking for the right kind of broach for your project, contract job or other application, Colonial Tool is the leader in building high-quality broaches. 

Here are some applications of broaching that may align with your own needs:

  • Automotive The automotive industry relies on rapid and precise mass manufacturing. A significant number of materials used in cars are broached, including metals of both a ferrous and non-ferrous nature. Additionally, the right kinds of plastic are broachable. Car and engine parts that need broaching include front and rear differentials, parking brakes, transmissions, engine manufacturing components and more. They will likely require the use of round, square, standard keyway and custom broaches to achieve the proper cuts.

  • Military The military-industrial complex is one of the greatest drivers of new technology in the modern world. They are responsible for innovations ranging from software to weaponry to land and air transport vehicles. The specifications on these devices are tight because of the rigorous use they undergo. To manufacture such parts quickly and in a cost-effective manner, all varieties of broaches are put into action.

  • Farm Tools and Implements Farm tools must be able to withstand a lot of strain, heavy use and demanding conditions. Some farm implements that may require broaching are cultivators, plows, rollers, slurry spreaders, reapers, harvesters of different types, balers, loaders and mixers. Parts both big and small need broaching, and they often need to have tight tolerances to ensure longevity and less mechanical strain.

  • Turbines Turbines are a critical feature in industries such as aerospace, automotive, marine and energy. Turbine broaching is a subset of broaching in which special broaches are used, often with horizontal broaching machines. Colonial Tools offers turbine broaches for any need you may have in this area.

The Cost-Effectiveness of Broaching

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It's no secret that high-quality broaches, particularly those that are custom-designed, cost more than other tools of comparable sizes. It is not uncommon to get some degree of sticker shock — however, when considering the longevity of a broach and how many parts it can create, it is one of the most cost-effective tools on the market.

Broaches are typically made of high-speed steel or carbide. High-speed steel has a relatively high percentage of carbon and an even larger percentage of tungsten. It is a hard material that can stand up to lots of repeated usage, and it's also a popular, affordable alternative to carbide. Carbide, on the other hand, is extremely hard and retains its sharpness over a long lifespan of broaching.

The best way to ensure your broaches give you the most bang for your buck is to have them regularly sharpened. Colonial Tool offers both repairing and rebuilding services for your broaches, which can increase their lifetime significantly. As an example, a broach used without sharpening might wear out after producing 10,000 parts. However, if it is sharpened after every 3000 parts, its lifetime could increase to 70,000 parts, which drops the cost per part to mere cents.

Sharpening and regrinding your broaches also keeps their tolerances tight. Because Colonial Tools prioritizes quick turnarounds, this also results in less downtime and higher profitability for your business. Broaches that have grown dull will produce less accurate parts — they can even begin cause errors in the part. This costs additional time and money, which regular sharpening will prevent.

In summary, although a broach is more expensive than other tools when considered as an upfront purchase, its long lifespan and ability to craft an inordinately large amount of parts makes it a worthwhile investment that pays itself off in a short amount of time. 

Come to Colonial Tool for Broaches, Broaching Tools and Repair

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Broaches are one of the most versatile, powerful tools available to machine shops, hobbyists and manufacturers today. If you're looking for the right broach tool to suit your needs, browse our selection of broaching tools and contact us to learn more about those that interest you. We pride ourselves on offering the highest-quality broaches available anywhere. 

Though the prices for our broaches tend to be higher than our competition, this is reflected in their quality and craftsmanship. A broach from Colonial Tool, when treated to regular sharpening and upkeep, will save you money in the long run. Even after other broaches have worn out and failed, a Colonial Tool broach will keep going strong. 

Colonial Tool offers many other services, as well, including:

Interested in learning more? Contact us today for a free quote.