Serrated Cutting: Techniques and Tools for Metalworking

Serrated cutting is a metal removal operation that can divide a piece into two or more parts by removing material between them. The manual process consists of the sawing and the forward movement of the saw. The effectiveness depends on operator skill and the number of sawing strokes per second.

Bow or Frame

This tool supports the saw blade. It consists of a rigid, U-shaped arch. At the ends of the arch are two mutually perpendicular blocks that hold the saw. One of these blocks is controlled by a mobile or wing nut, and a handle serves as a grip.

The arches of saws can be fixed or extensible. The advantage of the extensible type is that it allows the assembly of saw blades of various sizes.

Saw Blade

A saw blade is made of thin, laminated carbon steel, HS, or HSS (high-speed steel). It is fitted with teeth on one or both edges, and its ends have two holes for fixing it to the heels of the arch.

• Size: The most common size is 12 inches, approximately 300mm.
• Width: The distance between the contours of the blade, expressed in inches or millimeters. The most common widths are 1/2 inch (13mm) or 5/6 inch (25mm).
• Thickness: Typically 0.65mm.
• Step: 0.90mm.
• Grade or Cut: The length between the peaks of two consecutive teeth of the saw blade. The harder the material to be cut, the smaller the pitch of the teeth, and the blade will have fewer teeth. (Number of teeth per inch) can be thin, medium, or coarse.

Saw blades are constructed so that their teeth cannot become cramped during the cutting operation. Disposition: Corrugated or tooth set.

Saw Cords

These are made up of thousands of tungsten carbide particles permanently bonded to an alloy steel cord. The cut is made by abrasion, not removal. They are used for making curved cuts in materials like steel. Features: The edge is never dull, muffled, or broken. It cuts in both the forward and backward strokes, increasing cutting capacity. They are practically unbreakable, avoiding the risk of accidents.

Operations Prior to Sawing

• Choose the saw blade that best suits the work. Consider the type of material to be sawed and its thickness.
• Three teeth of the blade must always be in contact with the metal to avoid breaking the grip and the blade.
• Ensure the blade is clean and in perfect condition.
• Mount the blade on the bow with the teeth facing forward.
• Tension the blade sufficiently to secure it to the bolt, preventing swaying or vibration.

Performing the Sawing Operation

• Maintain a comfortable position during work.
• The rate of movement varies: 30 or 40 strokes for hard materials, 50 or 60 for soft materials.
• The saw is held by the handle with the right hand (for right-handed individuals) to advance and with the left hand at the end to prevent rolling.
• To start the cut, make a small notch to guide the saw through the piece correctly.
• Apply pressure during the forward motion and cool the cutting area with emulsions, water, or oil, depending on the material.