• Explanation: Disc diameter is the length of the disc. Some manufacturers measure this from one end of the physical disc to the other, whereas others measure it from one end of the cutting blade to the other.

Disc shape also varies from manufacturer to manufacturer, as well as disc height.

Company specifications

New Holland: Discs on the MowMax II cutterbar of the center-pivot Discbine measure 23.4 inches in diameter. Not only are the discs larger, they have a “tapered skirt” design profile designed to provide a smoother transition of the crop to the conditioner.

In addition, New Holland exclusive ShockPro disc drive hubs absorb the impact before damage to drive components can occur and are quick to replace in the field so you can keep cutting when the weather is right.

Heavy, full-coverage, cast rock guards provide additional protection to the cutterbar. It reduces costs and limits operator downtime to less than 10 minutes to change the hub.

Vermeer: Up to this point, Vermeer mowers and mower conditioners have offered a disc cut diameter of 19.7 inches. However, with the introduction of a new mower conditioner line, the disc cut diameter will be 23.1 inches with the next-generation Q3 cutterbar.

Case IH: Case IH offers a 24.3-inch diameter disc on center-pivot mower conditioners and SP windrower disc heads. The larger discs allow you to cut lower to the ground with less cutterbar tilt, resulting in better cut quality and reduced scalloping.

The larger discs also allow you to get the same tip speed with lower rpm, resulting in less blow-down, and ultimately, a cleaner cut.

The wider discs have a flatter profile, which helps move material over the cutterbar and into the conditioning system, minimizing crop bunching and crop re-cutting on the cutterbar. Balancing disc size with the drive and conditioning systems gives a balanced harvesting system.

Kuhn North America: Our Optidisc cutterbars utilize discs and cones that are 16 inches long by 10 inches wide. On this cutterbar, we also utilize differential disc spacing, which provides more blade overlap in areas where discs diverge away from each other, helping eliminate streaking in light crop conditions compared to other equally spaced cutterbars on the market.

In addition, our cutting discs have a low height, which allows our blade attachment to be low; therefore, we can run the cutterbar at a much flatter angle to obtain a clean cut. This also helps reduce ash and rock incorporation into the crop and significantly decreases dishing (inconsistently cut crop height).

Why it matters

The combination of discs and conditioning systems work together to provide cleaner cutting, better crop flow and more consistent conditioning. A wide swath allows more sun exposure to the crop, improving natural drying.

Disc diameter can have a big impact on a disc mower or conditioner’s performance. With new, larger discs, crop flow is improved, resulting in greater windrow consistency, and ultimately, better bale formation.

Larger discs can also help extend disc life. Bigger and heavier components allow for more shock protection. A larger disc diameter reduces the need for more discs, minimizing horsepower consumption and maintenance needs.

Disc diameter is especially important when it comes to the durability of your mower or mower conditioner. A larger disc diameter size generally correlates to larger componentry and increased durability of the machine – from the cutterbar itself to the skid shoes and components of each individual disc.

One of the risks of a larger disc size, however, can be the potential of creating more wind generation that can contribute to a common problem on disc mowers: streaking. However, slowing the disc speed down and maintaining the blade tip speed can mitigate this potential issue.

Disc diameter matters because every disc should be sized correctly relative to the rotational speed of the disc when cutting. Properly sized discs, along with the correct quantity for a specific cutting width, ensure customers will get well-cut crop in various conditions, whether thick or thin. In addition, on mower conditioners, this is important because correctly sized discs ensure a consistent flow of crop to the conditioning system.

How much weight should this feature carry in my buying decision?

Case IH: Depending on your operation’s needs, disc diameter could be an important factor to consider when buying a disc mower conditioner. If you’re looking to improve windrow consistency and bale formation, consider larger discs that will better handle crop flow.

Do you work on a lot of rough terrain? Larger, heavier components provide more shock absorption. Also, if you’re looking to minimize maintenance needs while maximizing efficiency, then going with larger discs will reduce the number of discs needed, lowering horsepower consumption.

New Holland: The size of the discs should have a definite bearing on a producer’s buying decision. In the haymaker’s race against the weather, having a disc mower-conditioner with larger discs allows producers to harvest forage more efficiently when weather conditions are ideal, resulting in higher overall forage quality.

Vermeer: There are several other factors – such as desired cutting width, horsepower requirements, transport width and more – that will likely play a more significant role in an operator’s buying decisions.

However, when it comes to the consideration of durability, disc diameter can hold significant weight in the decision-making process.

For example, custom operators and full-time farmers who mow thousands of acres a year or potentially see rougher terrain may place more weight on disc diameter due to the overall durability.

Kuhn North America: It is very difficult for a typical customer to properly evaluate cutting performance based on disc diameter alone. A true demonstration in the crop conditions they face is the ideal way to determine if a certain manufacturer’s disc diameter works for them.

This is primarily due to the relation between disc diameter, disc quantity and disc rotational speed. Kuhn, as the inventor of the disc cutterbar, has had over 47 years of experience determining the right formula for clean cutting in different types of crop. This includes thick and thin stands of legumes, like alfalfa, as well as the multitude of grasses we harvest across North America.  FG