Broaching is a metalworking technique used when precise machining is needed, particularly for irregular forms. Splines, keyways, flat surfaces, and circular and non-circular holes are examples of surfaces that are often machined.
A toothed tool is used in the machining process of broaching to remove material precisely and accurately.
Although both rotary and linear broaching services are used to provide various machining finishes, production broaching is usually only employed for high-volume manufacturing and precise applications.
Well, in this reading, we’ll explore what broaching is, its applications, components, diagram, types, processes, advantages, and disadvantages.
Let’s begin!
What is Broaching?
A toothed tool known as a broach is used in the machining process of broaching in order to remove material. Broaching comes in two primary varieties: rotary and linear.
The most popular method, linear broaching, creates the cut by running the broach in a straight line across a workpiece surface.
A broaching machine, commonly referred to as “broach,” uses linear broaches. In rotary broaching, an axisymmetric form is cut by rotating and pressing the broach into the workpiece.
A screw machine or lathe uses a rotating broach. Both methods are highly efficient since the cut is made in a single broach pass.
When accurate machining is required, particularly for irregular forms, broaching is used. Splines, keyways, flat surfaces, and circular and non-circular holes are examples of surfaces that are often machined.
Small to medium-sized castings, forgings, screw machine components, and stampings are examples of typical workpieces. When used for large production runs, broaching is typically preferred over alternative methods, despite the fact that it can be costly.
Applications
Below are the major uses of broaching in various applications:
- Broaching is used in various fields, including hand tools, appliances, plumbing, automotive design, farming equipment, and military and industrial applications.
- Their primary use is in producing high-volume parts requiring accurate, repetitive, and complex cuts.
- Broaching is used on materials with a hardness rating between 26 and 28 Rockwell C.
- Broaching is extensively used in the automotive industry for manufacturing components like gears, shafts, axles, and spline shafts.
- In the aerospace industry, broaching is used to create turbine blades, engine parts, and aerospace gears.
- In medical equipment manufacturing, broaching ensures the creation of intricate components with tight tolerances.
- In firearms manufacturing, it is used to create features like rifling in gun barrels, ensuring accuracy and performance.
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Parts
Below are the major parts of a broaching machine:
- Broach Tool
- Workpiece
- Broaching Machine
- Fixture
- Cutting Fluid
Diagram
Types of Broaching Machines
Below are the various types of broaching machines:
- CNC Broaching
- Turn Broaching Machine
- Rotary Broaching Machine
- Continuous Broaching Machine
- Surface Broaching Machine
- Vertical Broaching Machine
- Horizontal Broaching Machine
CNC Broaching
Recent technical advancements have made it possible to employ Computer Numerical Control (CNC) tools for the broaching process. Both linear and rotary procedures may be used to broach parts in a single phase.
Tools, tool bodies, and holders that may be used in the CNC process have been created by broaching companies.
Tool holders and indexable insert broaching tools are features of CNC broaching. Several specialised inserts are made possible by the unique tool holders. Among the several types of CNC broaches are rotary or swaying, punch, keyway, splines, polygons, and serrations.
Turn Broaching Machine
When surfaces require a high level of quality, turn broaching machines are used for spiral, linear, and circular cutting. By rotating the crankshaft between centres, the tool’s multiple inserts can remove material.
The parts that make up a turn broaching machine can roughen or finish. The tool depends on the machine type.
The stock removal rate’s requirements determine the roughing inserts and their segments. The flexible cartridges in the finishing parts are perfect for achieving precise tolerances.
Rotary Broaching Machine
Rotary broaching is another type of broaching often referred to as wobbling broaching. It is an accurate technique for creating interior or exterior polygonal shapes.
During its operation, the rotating broaching produces a chiselling or scalloping effect because the cutting tool is positioned at an angle of one degree to the workpiece’s centre.
A lathe or mill with a horizontal or vertical spindle machine that allows the spindle to spin freely can be used for rotary broaching. Hexagons, squares, spur gears, splines, involutes, keyways, serrations, numerals, and letters are among the forms that may be made by rotary broaching.
Continuous Broaching Machine
Continuous broaching involves holding the broach steady while the workpiece is continuously moving. The motion may be circular, horizontal, or straight.
In this type of broaching, the workpieces are loaded onto a fixture that is attached to a chain in horizontal continuous broaching. The process of continuous broaching is used to cut comparable components simultaneously.
Surface Broaching Machine
In these types of broaching machines, excess material is removed from a workpiece’s surface using surface broaching equipment. To create flat or curved surfaces, the cutting tool moves across the workpiece.
A surface broaching machine is special because the cutting tool is fastened to a ram that is pushed past the workpiece.
The machine’s design will determine whether the ram moves vertically or horizontally. Duplex broaching refers to the possibility of a surface broaching machine with two rams.
Vertical Broaching Machine
There are two types of vertical broaching machines: push and pull. The push type is more common. Unlike horizontal devices, vertical devices save floor area and are used to operate platforms or pits.
Modern vertical broaches are also utilised for electro-mechanical and hydraulic drives.
Horizontal Broaching Machine
Horizontal broaching machines are used for both interior and exterior broaching, and they employ the pull-type approach. A horizontal machine consists of a driving mechanism, a bed, and a broach pilot.
Keyways, splines, slots, round holes, and internal forms are the primary broaches on a horizontal machine. Horizontal machines are ideal for large workpieces and lengthy broaches, although they do require floor space.
How Does Broaching Work?
Whether internal or surface broaching is being employed can determine the broaching technique.
During their operations, the workpiece may be stationary and the broach moved against it, or the broaching tool may stay still while the workpiece is pushed against it.
Broaching internally is more complicated. A work holder, which serves as the broaching machine’s mount, is required to hold the workpiece in place while using an internal broach. The broach is then lowered into the workpiece using the machine’s lift.
After the lift releases the follower, the machine’s puller grabs hold of the broach pilot and pulls the entire broach through the piece. The broach then reconnects with the lift once the workpiece has been removed.
Below are the steps involved in the broaching process:
1. Setup and Fixturing: Secure the workpiece using a fixture on the broaching machine. Also, ensure proper alignment for accuracy.
2. Broach Selection: Choose the right broach based on desired features and workpiece material.
3. Broaching Operation: Guide the broach through the workpiece, cutting away material with each pass. The process can be linear or rotary, depending on the machine and broach.
4. Inspection: Thorough inspection of the workpiece post-broaching to ensure specifications and tolerances are met.
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Advantages and Disadvantages of Broaching
Broaching is a process that offers high production rates, high dimensional and form accuracy, and surface finish. It requires only one motion of cutting, making design, construction, operation, and control simpler.
Broaching is suitable and economical for mass production and requires little skill to perform. It can be used for internal or external surface finishing, with a tolerance of +-0.0075 mm and a surface finish of about 0.8 microns.
Cutting fluid can be readily applied where it is most effective.
However, broaching has disadvantages, such as only being suitable for through holes and surfaces, being used only for light cuts, having limited cutting speed, and causing defects or damages in the broach.
Design, manufacture, and restoration of broaches are difficult and expensive, and a separate broach must be procured for changes in job size, shape, and geometry.
Broaching is only economical when the production volume is large, and large workpieces cannot be broached. High tool costs and difficulty in removing large amounts of stock are also challenges.
FAQs
What is the process of broaching?
Broaching is a machining process that involves removing material using a special tool called a broach. The broach is a multi-toothed cutting tool that progressively increases in size, enabling it to cut different parts of a workpiece in a single pass.
What is a broaching tool used for?
A broach is a tool used to cut 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.
What is the function of broaching?
Broaching is a material removal process where a special tool called a broach (or broaching tool), generally with a linear movement, removes the material in a progressive way.
The main characteristic of a broach is a longitudinal series of teeth arranged geometrically on a shaft or a plate.
What are the two types of broaching?
Internal broaching comes in two main types: rotary and vertical. Both are designed to enlarge holes within a workpiece.
