**Diameter of a cylindrical rod on which threads are cut is known as the Major Diameter.**

The Major Diameter is a critical dimension that determines the size of the threaded rod. It is the outermost diameter of the threaded section and plays a significant role in ensuring the functionality and compatibility of threaded components.

**Importance of Major Diameter:**

The Major Diameter serves several important purposes in threaded connections:

1. **Thread Engagement:** The Major Diameter determines the amount of contact between the male and female threads. Sufficient thread engagement is crucial to ensure a strong and secure connection. If the Major Diameter is too small, it may result in insufficient engagement, leading to weak connections and increased risk of thread stripping or failure.

2. **Thread Fit:** The Major Diameter also helps determine the thread fit. Thread fit refers to the level of tightness or looseness between the male and female threads. The fit can vary depending on the application requirements, such as clearance fit, interference fit, or tight fit.

3. **Compatibility:** The Major Diameter is standardized to ensure compatibility between threaded components. Various thread standards exist, such as the Unified Thread Standard (UNC, UNF), Metric Thread Standard (M), and British Standard Whitworth (BSW). These standards define the Major Diameter and thread pitch to ensure interchangeability and compatibility of threaded components.

**Thread Cutting Process:**

The process of cutting threads on a cylindrical rod involves removing material to form the thread profile. This is typically done using a lathe or a thread-cutting machine. The following steps are involved in the thread cutting process:

1. **Preparation:** The cylindrical rod is mounted securely in the lathe or thread-cutting machine. The tooling and cutting parameters are determined based on the desired thread specifications.

2. **Initial Cuts:** The initial cuts are made to rough out the thread profile. These cuts remove most of the material, leaving behind a rough surface that closely resembles the thread shape.

3. **Finishing Passes:** Finishing passes are made to achieve the final thread dimensions and improve the surface finish. These passes ensure the Major Diameter is precise and meets the desired specifications.

4. **Thread Verification:** After the cutting process is complete, the threaded rod is typically checked using thread gauges or other measuring instruments to verify that the Major Diameter is within the acceptable tolerance range.

In conclusion, the Major Diameter of a cylindrical rod on which threads are cut is a crucial dimension that determines the size, functionality, and compatibility of threaded connections. It is important to adhere to standardized thread specifications and ensure proper thread cutting processes to achieve accurate Major Diameter and reliable threaded components.

Pitch diameter if by thread rolling operation