Broaching is a machining process that uses a toothed tool called a broach to remove material. Broaches have multiple rows of teeth used to shape the workpiece into the desired form. As the broach is pushed or pulled through the workpiece, each successive tooth chips off a little more material, gradually shaping the workpiece to the required dimensions and finish. Broaching produces precision holes, slots and forms with a smooth surface finish in both ferrous and non-ferrous materials.
Key Types of Broaching Tools
There are several common types of broaching tools designed for different applications:
Rack Broaches
Rack broaches are used to cut internal straight flutes or slots in workpieces. They have teeth arranged in a straight rack pattern. Rack broaches are well-suited for high-volume production of small intricate parts with complex internal forms. They can quickly shape items like gears with many teeth.
Form Broaches
Form broaches contain teeth arranged in curved patterns to cut complex contours like oval, circular or irregular shaped openings. They are used to machine intricate external and internal contour surfaces on components for aerospace, medical and other precision applications. Form broaching provides an economical alternative to machining when complex contours are involved.
Pull Broaches
Pull broaches are designed to cut shoulders, angles, and forms on the outside diameter of parts. They have alternating sets of upper and lower teeth to cut in both directions of their stroke. During Broaching Tools, pull forces are used rather than push forces. Pull broaches work well for cutting forms on small, tightly tolerance workpieces.
Slipline Broaches
Slipline broaches can cut odd-shaped internal forms by using narrow teeth that follow the desired contour. They are efficient for producing unusual shapes that rack, form or pull broaches may not be suited for. Slipline broaching is generally a more expensive process than straight rack broaching but enables complex odd-form production.
Construction of Broaching Tools
Broaching tools are available in solid tool steel as well as brazed-tooth and inserted-tooth configurations. Solid tool steel broaches offer rigidity for heavy-duty applications but are more difficult to produce. Brazed-tooth broaches involve brazing pre-formed tool steel teeth to a shank or holder for easier manufacturing. Inserted-tooth broaches use replaceable carbide or high-speed steel teeth inserted into pockets in the tool body, allowing economical tooth replacement.
Applications of Broaching
Broaching finds diverse applications across many industries for shape generation, machining of holes and slots, gear cutting, and other forms and profile production needs:
Automotive applications: Broaching is heavily used in automotive manufacturing for cutting splines, keys and other features on transmission, brake and steering components. Broached parts offer precision mating with fewer defects over long production runs.
Aircraft components: Broaching aircraft engine parts, airframe components and other safety-critical parts produces dimensions within very tight tolerances required for reliability and performance. Broaching delivers cost-competitive close-tolerance production.
Fastener industry: Broaching enables high-volume manufacture of precise internal threading, contours and forms on bolts, nuts, screws and other fasteners. It facilitates bulk production of consistent Thread Rolling parts.
Medical devices: Precision broaching creates complex internal and external forms, holes and slots for fluid-transferring needles, surgical instruments, implants and other disposable medical devices with stringent quality demands.
Tooling industry: Broaches are used to cut slots, splines and other precise shapes on toolroom fixtures, jigs, dies and molds for repeatable heavy-duty manufacturing applications across industries.
Benefits of Broaching
Key performance advantages that make broaching a production-friendly machining process include:
- High material removal rates allowing lighter-duty broaching for high-volume production tasks.
- Very close dimensional tolerances of ±0.0001 inch routinely achievable with good process control.
- Exceptional surface finishes down to 4 microinches Ra possible for hard-to-machine materials.
- Absence of burrs or torn metal edges on cut parts streamlines further processing or assembly.
- Long tool life lasting thousands of parts before resharpening is needed for most broaching applications.
- Little need for subsequent operatons like grinding or honing to achieve specifications.
- Process versatility in machining many common metals like steel, aluminum, titanium and more.
Broaching thus delivers precision shaping, slotting or profiling in high volumes for use across diverse manufacturing industries demanding rigorous quality and throughput demands. With ongoing technological advancements, broaching tools promises to play an ever bigger role in factory automation and lean production methodologies going forward.
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