Basic components of portable cutting knives

Structurally, both types of knives have a base plate, power system, handle, cutting blade, sharpening device and blade guard. Round knives operate with a one way thrust as the circular blade makes contact with the fabric, and vertical knives cut with an up-and-down action.

1) Blade 

Blades are mounted in a vertical position at a 90-degree angle to the cutting surface. Blades vary in shape, size, cutting action, and fineness of the cutting edge.

• A straight blade contacts the spread at a 90-degree angle; assuming the blade and spread are kept vertical, all plies, are cut at the same time. A rotary blade does not cut all plies evenly at the same time.

• A round blade contacts the spread at an angle; thus, the top ply is cut before the bottom ply.

Knife blades affect the quality of the cut. Factors that affect the performance of a blade are the blade edge, surface texture of the blade, coarseness or fineness of the blade edge, and blade composition. Blade edges may be straight with a flat surface, saw-toothed, serrated, or wavy with a striated surface. Straight-edge blades with a flat surface are general-purpose and the most widely used, while the other types are more specific to certain types of fabrics.

2) Base plate
The base plate is the foundation that supports and helps balance the cutting mechanism. Bases vary in shape and size, depending on the size and weight of the knife they support and the maneuverability needed. The base plate guides the knife in relation to the table surface and elevates the spread off the cutting table for contact with the blade. Base plates are supported by bearing rollers to facilitate maneuverability, and ease of movement. Edges of the plate are sloped and the front is curved, which easily slide the bottom ply and provide less fabric distortion. The base plate helps maintain the position of the blade at a 90-degree pitch.

3) Power system
The power system controls the motor and the potential cutting speed. The amount of power needed to cut a spread depends on the height of the spread and the density of the fabric to be cut. The horsepower of the motor determines the amount of thrust or cutting power of the blade. Motor size may be selected for the type of fabric and spread height that is typical for the plant. Higher speeds allow operators to move knives faster. Greater horsepower increases machine power, but it also may increase weight of the motor, which must be balanced by the blade housing and base plate.

4) Sharpening device
Sharpening devices appropriate for the specific blade type are found on almost all mechanized cutting equipment. Blades dull quickly when cutting a deep spread or dense fabric. As a blade becomes dull, it creates friction and may cause rough, frayed, or fused edges. Sharpening devices may be stone or emery wheels or abrasive belt sharpeners. Cutting blades are sharpened frequently during the cutting operation simply by touching the control.

5) Handle
All manually operated cutting devices have a handle for the operator to grip, guide, and propel the knife through the spread. The operator’s other hand is used to stabilize the plies ahead of the knife to prevent bunching of fabric.

6) Blade guard
A blade guard, when positioned at spread height, rests on the top ply to help stabilize the spread and to protect the operator’s hand. Metal mesh gloves are available as a safety device for cutters using vertical knives.