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Understanding the Role of Bedknives

Understanding the Role of Bedknives

True or False: The fine finish from a cylinder mower is down to luck?

It’s the time of year when advice on checking bedknives is regularly dispensed, and rightly so for those with high season fast approaching. However, it’s good to stop for a moment and understand how and why operating, adjustment and maintenance procedures are so important, especially when it comes to the critical end of the grass cutting process.

Bedknives play an important role in the fine finish expected from a cylinder mower. Along with the cylinder and the frame, the bedknife is one of the three main structural members in a cylinder cutting unit. The bedknife is attached to the bedbar and the assembly is mounted to the main frame in a manner that allows for paralleling and adjustment to the cylinder.

A cylinder mower cuts grass with a scissor-like shearing action as the moving helix-shaped blades pass over the stationary bedknife. The cutting action requires the bedknife and cylinder blades to be sharp, matched and in close relationship with each other, and the bedknife sharpened to be flat and square so the sharp edge touches the cylinder blades across their entire length.

If the bedknife is not perfectly flat, it is impossible to get the bedknife to touch the entire length of the cylinder. This is an essential part of the construction, making cylinder mowers precision cutting tools. Adjust any part of the construction process with, for example, ‘will-fit’ parts and the fit, form and function can be affected to leave a less attractive and less consistent after-cut appearance.

To understand the cylinder cutting theory fully, you need to understand the concept of the clip and shear point. A shear point is any single point of contact made between the cylinder blade and bedknife. The clip is the forward distance travelled between successive blade contacts at one shear point. As the cylinder moves forward it pushes the grass in front of it, while the cylinder blade gathers the grass as it moves toward the bedknife. The bedknife then pushes the grass toward the shear point, while the cylinder blade gathers it in front, creating a triangle.”

The fine finish expected from a cylinder mower is not down to luck, far from it. Understanding and appreciating that cylinder mowers are precision machines, requiring precision-engineered parts in order to achieve the best possible finish should help make the decision that ‘will-fit’ parts aren’t worth the negative impact on the turf.

The quote, “The bitterness of poor quality remains long after the sweetness of low price is forgotten,” rings true here. So, it’s recommended not to fall foul to the temptation of will-fit parts.

Toro bedknifes are precision-engineered for a superior quality of cut. Every bedknife Toro manufactures is designed to meet strict Toro engineering specifications to ensure the best quality of cut and after-cut appearance.
A true flatness of the knife extends their life and maximizes the quality of cut. They’re made of high carbon steel for ultimate durability and longevity, and do retain their edge for longer, meaning superintendents can mow longer without the need to adjust or replace as frequently.

To avoid downtime and ensure a premium after-cut appearance for longer, contact your local
Toro dealer.