The Parts of a Disc Plow

Since the dawn of the agricultural age, humans have been plowing their fields. The first plow was made of wood and, pulled by hand, carved up a narrow strip of soil at one pass. Later, moldboard plows, first pulled by beasts and then by tractors, would plow a wider strip of earth, but only one or two furrows at a time. Modern farmers use the disc plow, also called a disc harrow, to turn more ground in a single, more efficient pass of the tractor.

The disc plow is the modern version of field cultivating equipment.


The plow frame is the foundation for performance of the plow. It must be strong enough to support the weight of all the discs and other parts but lightweight enough to allow efficient pulling. The hub supports are part of the frame and are set at a pitch and angle that allow maximum penetration of the soil by the discs.


The plow assembly must be flexible to meet modern demands in the field. The hitch is an important component of disc performance. The plow pivots at the hitch for a smooth turn and is set in a spring-loaded assembly for shock absorption. The modern hitch helps control weight transfer with a leveling control system and helps control sideways sliding of the plow. Hitches ideally can be shifted front or back to minimize over-biting of the front discs.

Disc Blades

The disc blades are the actual cutting parts of the plow. They are made of heat-treated heavy-duty cast steel and come in a round or notched design. The notched blade is designed to create a more efficient cutting edge, particularly for plowing sod. The blades range in diameter from 16 inches to 36 inches in diameter and come with either round or square holes for attaching to the hubs.

Gauge Wheel

The gauge or furrow wheel rests on axles at the sides of the plow and is designed to ensure a constant depth of penetration by the discs on uneven ground, which frees the operator from constant depth monitoring. To create side-to-side stability in the plow, it cuts at an opposing angle from the main disc blades.

Miscellaneous Parts

There are several parts required to connect the frame, discs, hubs and gauge wheel. These include cast spools, end washers, bumper washers, axle nut locks, space tubes and slack washers.

Katie Gwinn

Katie Gwinn has been writing professionally since 1972. She has been published by the U.S. Department of Education, as well as regional newspapers and private publications as a columnist and writer. Gwinn holds a Bachelor of Arts in liberal arts from California State University.