To study about the broaching process.

Experiment No.: 08

To study about the broaching process.

Introduction:

  • Broaching is a method of removing metal by pushing or pulling a cutting tool called a broach.
  • A broach is a multiple-edge cutting tool that has successively higher cutting edges along the length of the tool.
  • It is generally limited to the removal of about 6mm of stock or less.

Types of Broaching Process:

  1. Internal Broaching
  2. External Broaching
  3. Pull-Type Broach
    • Longer in length.
    • Subjected to tensile broaching.
    • Used for internal broaching.
  4. Push-Type Broach
    • Shorter in length.
    • Subjected to compressive force.
    • Used for external broaching.

Elements of a Broach:

  1. Pull End – Designed for engagement of the broach with the broaching machine through the use of a puller head.
  2. Front Pilot – Centers the broach in the hole.
  3. Roughing Teeth – The initial set of teeth responsible for the majority of material removal.
  4. Semi-Finishing Teeth – Follow the roughing teeth and remove less material than roughing teeth.
  5. Rear Pilot and Follower Set – Provided at the rear end of the broach to support it after the last tooth.

Broach Tool Nomenclature:

  1. Cut Per Tooth – The progressive increase in tooth height from tooth to tooth of approach.
  2. Cutting Teeth – Provided in three separate sections along the length of the broach.
  3. Tooth Gullet – The space between two successive teeth to accommodate the generated chip.
  4. Tooth Land – The top portion of a tooth, a slight clearance angle is provided to reduce friction.
  5. Pitch – The linear distance from the cutting edge of one tooth to the corresponding edge of the next tooth.
  6. Rack or Hook Angle – Provided on the face based on the work material. In general, rack angle increases as ductility increases.
  7. Back-Off and Clearance Angle – Clearance provided to prevent rubbing of the sides of the slot produced with the tool. This is 1.5 to 2 degrees for both cast iron and steel.

Broaching Machines:

Broaching machines are the simplest of all machine tools. There are two principal types:

  1. Horizontal Broaching Machine
  2. Vertical Broaching Machine

Horizontal Broaching Machine:

  • Also known as universal machines.
  • Capable of performing a wide range of operations.
  • Used for either internal or external broaching.
  • All horizontal machines are of the pull type.
  • Used for broaching keyways, splines, slots, round holes, and other internal shapes.

Vertical Broaching Machine:

  • Available in either push or pull type.
  • Push type is the most popular.
  • Used in multiple operations.
  • Modern vertical broaches are offered with both hydraulic and electro-mechanical drives.

Broach Tool Materials:

Broaches are made from materials with properties required for cutting tools, such as high strength, hardness, toughness, and wear resistance.

  1. High Carbon Steel
    • Suitable for light work.
    • Not suitable for production work.
  2. High-Speed Steel (HSS)
    • Suitable for light work.
    • Used for heavy-duty work and good surface finish.
  3. Cemented Carbide
    • Suitable for hardened materials like cast iron and steel.
  4. TiN (Titanium Nitride) Coated Carbide – Used for increased wear resistance.

Conclusion: –

To be written by student.

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