How to Choose the Right straight knife

We have already discussed in the previous article the different uses and properties of round knives and straight knives, and in this article, we will continue with a more in-depth look at these two types of blades. In addition, we will also discuss how to choose the right blade profile and material. This is especially important when selecting blade profiles and types for shearing jobs.

The following is an introduction to the content

1. An expanded introduction to straight knives and round knives

2. How to choose the right shape of the blade

An Expanded Introduction to straight knives and Circular Knives

As we know, there are 2 main types of blades most commonly used for sharing work, namely round knives and straight knives. Round knives are also known as disc-shaped blades, and straight knives are also known as flat blades. Typically, straight knives are mainly used for high-speed operations or for slitting high-density materials. Round knife blades are usually thinner than straight knives and can be stamped in high-volume production. Circular knives differ from straight knives because, as their name implies, they have a concave or "disc" geometry. In addition, the circular cutter is supported by a collar or spring to reduce excessive lateral loading forces from the driven shaft to the shaft arrangement. The disc-shaped blade design is suitable for shaft-to-shaft systems and for tool holders without tilt angle adjustment. Typically, a coil spring behind the blade creates a lateral load force for the upper tool. In turn, this creates a tilt angle for the blade. Because straight knives are made of raw material rather than stamped material, they are typically more expensive than round knives. As a result, it is easier to produce straight knives in large quantities than other alternatives.

How to choose the right shape of the blade

When choosing between the above two types of blades, the following aspects need to be considered.

The lateral load force required by the material to be cut

Typically, paper mills are most likely to use straight knives because of the high operating speeds required in paper mills. For cutting lighter materials, such as film, foil, nonwovens, etc., a round knife is usually preferred. Now, with either round or straight knives, you need to choose the circumferential edge of the processing blade. Three options are included here, namely one bevel, two bevels, and two bevels with relief.

The purpose of beveling

The correct angle of the blade bevel is critical for certain applications, so let's explain the purpose of the bevel, which includes:

l Allowing the blade to present a sharp, thin edge on the material.

l Minimizing the amount of material deformation caused by insert penetration.

l Providing a strong, durable, and reliable cutting edge.

Single bevel inserts are better suited for heavier materials and speed up to 4,000 - 5,000 fpm. Single bevel inserts produce more dust than multiple bevel inserts.

Double bevel blades are better suited for medium to light materials running at speeds of up to 8,000 fpm or more. They are the most commonly used blades in almost all industrial slitting markets today.

Double hollow ground bevel blades are suitable for slitting light materials and adhesives. They provide a small area for adhesion to sticky materials. Due to the limited speed, they generate much less dust because the slit edge must pass through fewer paths and the edge cutting profile is usually very clean.

The most important thing to note in selecting the right blade is that each material to be cut is different because even in the same type of material such as paper and nonwovens, the composition, thickness, and basis weight of the material can vary.