Broaching & Sawing

Process Definition & Working Principle

Broaching

Broaching is a highly productive and precise subtractive manufacturing process that utilizes a multi-toothed cutting tool called a broach. The defining characteristic of this process is that the tool performs a single linear stroke (either pulling or pushing) relative to the workpiece. The individual cutting teeth of the broach are arranged in a series, with each successive tooth standing slightly taller (or wider) than the preceding one. This step-up in height is known as the rise per tooth (RPT) or step-per-tooth, which defines the uncut chip thickness removed by each individual tooth.

The physics of the process involve three sequential cutting zones on a single tool:

1. Roughing Zone: The leading teeth have the largest RPT to maximize material removal efficiency.
2. Semi-Finishing Zone: The middle teeth have a progressively smaller RPT, reducing the cutting forces and improving geometric accuracy.
3. Finishing Zone: The trailing teeth have zero RPT (they are identical in size). They burnish and calibrate the profile to its final tolerances, neutralizing elastic spring-back of the workpiece.

Broaching is classified into pull broaching (where the tool is pulled through the workpiece under tension, eliminating buckling risk for long tools) and push broaching (where a shorter, stockier tool is pushed through the part using an arbor press or vertical ram).

Sawing

Sawing is a primary metal cut-off process used to divide raw bar stocks, structural profiles, or plates into specific billet lengths. It relies on a multi-toothed blade to progressively shear away material along a narrow path called the kerf. Three major industrial subcategories are utilized:

Kinematics, Axes, & Machine Configuration

Broaching Machine Configurations

Broaching machines are engineered to deliver exceptionally rigid linear motion. The primary kinematic axis is the linear Z-axis, aligning with the stroke of the broaching ram. For manufacturing helical profiles, a rotational axis (C-axis) is coupled with the Z-axis. In modern CNC broaching centers, this synchronization is electronically geared; in legacy mechanical setups, it is driven by a helical lead-bar (guide bar).

The machines are structurally categorized as: