What is a Broaching Tool? | Parts of Pull-Type Broach Tool | Internal and External Broaching

What is a Broaching Tool?

A broaching tool is a cutting tool used to machine internal or external surfaces of a workpiece. It is a type of cutting tool that uses a series of teeth or cutting edges to remove material in a controlled manner. Broaching tools are commonly used for shaping and sizing holes or grooves in workpieces.

A typical broaching tool consists of a series of cutting teeth or edges arranged in a linear sequence on a shaft. The teeth are usually in a progressively larger size to remove material in stages. The broaching tool is inserted into the workpiece and moved linearly or rotated to remove material from the workpiece.

Broaching tools can be classified into two types: internal and external broaching tools. Internal broaching tools are used to remove material from the inside of a workpiece, while external broaching tools are used to remove material from the outside of a workpiece. The teeth of an internal broaching tool are arranged in a helical pattern, while the teeth of an external broaching tool are arranged in a linear pattern.

Broaching tools are used in a wide range of industries, including automotive, aerospace, medical, and electronics. They are highly efficient tools that can produce accurate and consistent results, making them ideal for high-volume production applications.

The Process of Broaching

Broaching is a machining process that uses a broach, a cutting tool with a series of teeth or cutting edges, to remove material from a workpiece to create a specific shape or pattern. Here are the steps involved in the broaching process:

1. Choose the broach: Select a broach that is appropriate for the size and shape of the workpiece and the desired result.
2. Set up the workpiece: Secure the workpiece in the broaching machine or fixture, ensuring that it is properly aligned and clamped.
3. Align the broach: Position the broach in the machine or fixture and align it with the workpiece using the pilot.
4. Start the machine: Turn on the broaching machine and slowly feed the broach into the workpiece.
5. Begin cutting: The cutting teeth on the broach progressively remove material from the workpiece as it is pushed through. The broaching process is usually done in a single pass, although some complex shapes may require multiple passes.
6. Remove the broach: Once the broaching process is complete, retract the broach from the workpiece.
7. Inspect the workpiece: Check the workpiece for accuracy and quality, and make any necessary adjustments.
8. Finish the workpiece: Depending on the desired result, additional finishing processes such as grinding or polishing may be required to achieve the final surface finish.

Broaching is a versatile and precise machining process that is commonly used to create keyways, splines, gears, and other complex shapes in a wide range of materials.

Internal and External Broaching:

Internal broaching and external broaching are two types of broaching processes used to remove material from the inside or outside of a workpiece, respectively.

Internal broaching involves removing material from the inside of a workpiece to create a specific shape or size of hole or cavity. The broaching tool used in internal broaching has a series of cutting edges arranged in a helical pattern, and the tool is rotated and moved linearly to remove material in a controlled manner. Internal broaching is commonly used in the automotive, aerospace, and medical industries to create holes in engine blocks, transmission cases, and medical implants, among other applications.

External broaching involves removing material from the outside of a workpiece to create a specific shape or size of groove or contour. The broaching tool used in external broaching has a series of cutting edges arranged in a linear pattern, and the tool is moved linearly along the surface of the workpiece to remove material in a controlled manner. External broaching is commonly used in the aerospace and defense industries to create keyways, splines, and other precision features on shafts and other components.

Both internal and external broaching can be used to create precise and repeatable shapes and sizes in a wide range of materials, including metals, plastics, and composites. However, the specific broaching process used depends on the desired shape and size of the feature being created and the requirements of the application.

Parts of Pull-Type Broach Tool:

A pull-type broach tool is a type of broaching tool that is used to remove material from the inside of a workpiece. It is commonly used in the production of parts that require precise internal features, such as gears, splines, and keyways. The main parts of a pull-type broach tool include:

1. Broach Body: The broach body is the main component of the broaching tool and is typically made of high-strength steel. It contains the cutting edges or teeth that remove material from the workpiece.
2. Pilot: The pilot is a precision ground section of the broach body that centers the tool in the workpiece and helps maintain the correct alignment during the broaching process.
3. Puller Collar: The puller collar is a threaded collar that is attached to the broach body and is used to pull the broach through the workpiece during the broaching process.
4. Shims: Shims are thin, flat pieces of metal that are used to adjust the position of the broach teeth in the broach body. They are placed between the teeth and the broach body to ensure that the teeth are properly aligned and spaced.
5. Chip Breaker: The chip breaker is a feature of the broach teeth that helps to break up and remove the chips of material that are produced during the broaching process. This helps to prevent the chips from interfering with the broaching process and damaging the workpiece.
6. Coolant Holes: Coolant holes are channels that are machined into the broach body to allow coolant to flow through the tool and onto the cutting edges. This helps to reduce heat buildup and prevent damage to the broach and the workpiece.
7. Retainer: The retainer is a component that holds the broach in place during the broaching process. It is typically made of a high-strength material, such as steel or carbide, and is designed to withstand the forces and stresses of the broaching process.

Nomenclature of External Broach:

An external broach is a cutting tool used to remove material from the outside of a workpiece to create specific shapes or features, such as splines, keyways, or gears. The nomenclature of an external broach typically includes the following components:

1. Broach body: The main part of the broach that contains the cutting edges or teeth. The broach body is usually made of high-speed steel or carbide.
2. Teeth: The cutting edges on the broach body that remove material from the workpiece. The teeth are typically arranged in a linear pattern along the length of the broach.
3. Pilot: A precision ground section of the broach body that centers the broach in the workpiece and maintains its alignment during the cutting process. The pilot is usually located at the front of the broach.
4. Shank: The part of the broach that is held in the broach holder. The shank is typically square or rectangular in shape and is designed to fit tightly in the holder to prevent slipping during the cutting process.
5. Cutting edge angle: The angle at which the teeth are ground on the broach body. The cutting edge angle can vary depending on the material being cut and the type of feature being created.
6. Pitch: The distance between adjacent teeth on the broach. The pitch is measured from the center of one tooth to the center of the next and can vary depending on the desired feature size and shape.
7. Land width: The width of the land, or flat section, between adjacent teeth on the broach. The land width can affect the cutting forces and chip formation during the cutting process.
8. Lead angle: The angle at which the teeth are tilted in relation to the axis of the broach. The lead angle can vary depending on the type of feature being created and the material being cut.
9. Chamfer angle: The angle at which the cutting edges are chamfered to reduce the risk of chipping or breakage during the cutting process.

The specific nomenclature of an external broach can vary depending on the manufacturer and the specific application.

Types of Broaching Tool

Broaching is a machining process that is used to remove material from a workpiece to create precise shapes or features. There are several types of broaching processes, including:

1. Internal broaching: This process involves removing material from the inside of a workpiece to create a specific shape or size of hole or cavity. Internal broaching is commonly used in the automotive, aerospace, and medical industries to create holes in engine blocks, transmission cases, and medical implants, among other applications.
2. External broaching: This process involves removing material from the outside of a workpiece to create a specific shape or size of groove or contour. External broaching is commonly used in the aerospace and defense industries to create keyways, splines, and other precision features on shafts and other components.
3. Surface broaching: This process involves removing material from the surface of a workpiece to create a specific shape or contour. Surface broaching is often used in the production of turbine blades, where the blades are shaped by broaching the surface of the blade.
4. Continuous broaching: This process involves using a broaching tool that has multiple cutting edges arranged in a helical pattern. The tool is rotated and moved linearly to remove material in a continuous process. Continuous broaching is often used in the production of gears and other high-precision components.
5. Rotary broaching: This process involves using a broaching tool that is rotated around a fixed axis while being pressed into the workpiece. The tool has a single cutting edge that creates the desired shape or feature as it rotates. Rotary broaching is often used to create hexagonal and other non-circular shapes in small components.
6. Keyway broaching: This process involves using a broaching tool to create a keyway, which is a groove or slot in a shaft or other component that allows it to be attached to another component. Keyway broaching is often used in the production of gears, sprockets, and other mechanical components.

Each type of broaching process has its own advantages and disadvantages, and the specific process used depends on the desired shape and size of the feature being created and the requirements of the application.

Broaching Tool Components

A broaching tool is a cutting tool that consists of several components that work together to remove material from a workpiece. Here are the main components of a broaching tool:

1. Broach body: The main body of the broaching tool, which is held in the broaching machine and guides the cutting teeth through the workpiece.
2. Cutting teeth: The sharp edges on the broaching tool that remove material from the workpiece. Cutting teeth are located on the outer edges of the broach body and are arranged in a specific pattern or shape.
3. Land: The flat surface between the cutting teeth that provides support and stability to the broaching tool.
4. Chip grooves: The grooves or spaces between the cutting teeth that allow chips to be cleared during the cutting process.
5. Pilot: A guide on the end of the broaching tool that centers the broaching tool in the workpiece and keeps it aligned during the cutting process.
6. Shank: The part of the broaching tool that is held in the broaching machine. The shank may be square, hexagonal, or have other shapes to fit different types of broaching machines.
7. Broach angle: The angle of the cutting edges in relation to the axis of the broaching tool. The broach angle determines the type of cut and the amount of material that is removed.
8. Pitch: The distance between the cutting teeth on the broaching tool. The pitch is an important factor in determining the surface finish of the workpiece.
9. Relief: The space between the land and the cutting teeth that allows chips to clear during the cutting process.

Each component of the broaching tool is designed to work together to produce a specific cutting pattern or shape in the workpiece. The broaching tool can be customized with different combinations of components to produce different types of cuts and shapes.

Uses of Broaching Tool

Broaching tools are used in a variety of applications where precision machining is required. Here are some common uses of broaching tools:

1. Keyway cutting: Broaching tools are commonly used to create keyways, which are slots in shafts that allow for the insertion of keys to secure gears or other rotating components.
2. Splining: Broaching tools can be used to create splines, which are ridges or teeth on the surface of a shaft that provide a positive drive connection between two rotating components.
3. Gear cutting: Broaching tools can be used to create precise gear teeth profiles on gears for use in various types of machinery.
4. Surface finishing: Broaching tools can be used for precision machining of surfaces, such as to create precise internal or external shapes, grooves or features.
5. Automotive applications: Broaching tools are often used in the automotive industry for machining engine components, such as connecting rods, rocker arms, and valve lifters.
6. Aerospace applications: Broaching tools are used in the aerospace industry for machining components such as landing gear parts and hydraulic valve bodies.
7. Medical equipment: Broaching tools are used in the production of medical equipment, such as orthopedic implants, for creating precise shapes and features.
8. Firearms manufacturing: Broaching tools are used to create rifling in gun barrels, which is the spiral pattern of grooves cut into the inner surface of the barrel to impart spin to the bullet and improve accuracy.

Overall, broaching tools are used in many applications where precision machining of complex shapes is required, making them an important tool in the manufacturing industry.

Advantages and Disadvantages of Broaching Tool

Broaching tools offer several advantages and disadvantages in machining applications. Here are some of the main advantages and disadvantages of using a broaching tool:

Advantages:

1. High precision: Broaching tools are designed to produce highly accurate cuts and shapes with tight tolerances.
2. Versatility: Broaching tools can be used to cut a wide range of shapes and sizes in various materials.
3. Efficiency: Broaching tools are efficient in removing material and can often complete a cut in a single pass.
4. Reduced tool wear: Broaching tools are designed to distribute the cutting forces evenly, which helps to reduce tool wear.
5. Improved surface finish: Broaching tools produce smooth surface finishes with minimal surface roughness, reducing the need for additional finishing processes.

Disadvantages:

1. Initial cost: The initial cost of broaching tools is relatively high compared to other cutting tools, which can be a disadvantage for small-scale manufacturing.
2. Limited flexibility: Broaching tools are designed to produce a specific shape, which limits their flexibility compared to other machining processes such as milling or drilling.
3. Material limitations: Broaching tools are typically designed for use on softer materials, such as aluminum, brass, and plastic, and may not be suitable for harder materials such as steel.
4. Setup time: Setting up a broaching tool can be time-consuming and requires specialized knowledge and equipment.
5. Surface damage: Broaching tools can cause surface damage or deformation to the workpiece if the cutting forces are not distributed evenly or if the tool is not properly aligned.

Overall, broaching tools offer high precision and efficiency in producing complex shapes and patterns, but they may be limited in flexibility and may not be suitable for all materials and applications. Careful consideration of the advantages and disadvantages should be made when deciding whether to use a broaching tool for a specific machining operation.

Broaching Tool Design Terms

1. Broach: A cutting tool that has a series of teeth or cutting edges that progressively increase in size, used to create a specific shape or pattern in a workpiece.
2. Pilot: A guide that helps to center and guide the broach into the workpiece.
3. Shank: The main body of the broach that is held in the machine tool.
4. Cutting teeth: The sharp edges on the broach that remove material from the workpiece.
5. Land: The flat surface between the cutting teeth that provides support and stability to the broach.
6. Relief: The space between the land and the cutting teeth that allows chips to clear.
7. Broach angle: The angle of the cutting edges in relation to the axis of the broach.
8. Pitch: The distance between the teeth on the broach.
9. Tolerance: The allowable variation in size or dimensions of a broach or workpiece.
10. Finish: The surface quality of the workpiece after it has been broached.