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Disc Harrow Requirements

Disc Harrow Requirements

Disc Harrow Requirements

reprinted from Farm Practices by Allis Chalmers Co.

We especially emphasize here the expected requirements of a disc harrow which should not be overlooked before taking a harrow to the field. One of the most important requirements is disc blade concavity, that is, correct concavity. Further along we set forth the purposes of disc concavity. We feel it is important enough to devote the extra time and words in a discussion of the subject, because seldom is disc concavity talked about, and very few know that there is difference enough to cause good and bad work. Almost everyone has the idea that discs are all alike, that curvatures and sizes are the same, and if one style disc does good work, that any other style should do likewise. Proper disc angling is also a needed requirement in order to get even depth of all discs for deep or shallow work, and to get maximum pulverization in all soils. Here are some of the requirements:

  • Frame — Correct design very necessary; best materials should be used.
  • Hitch — Must hold gangs securely; must also get quick depth.
  • Gang Bolts — Should be large; durable; self-locking.
  • Bearings & Bushings — Need to be close fitting and made of best quality material.
  • Spacing Spools — Should be milled to fit the disc centers.
  • Scrapers — To be easy on disc blades.
  • Angling Controls — Quick and easy control is essential.
  • Gang Angling — Must be correct for all depths and speeds.
  • Follow Contours — Should be flexible as well as rigid.
  • Discs — Correct concavity; properly treated for long life; extra thickness.
  • Center Control — Should fill dead furrows and level back furrows.
  • Compacting Soil — Correct angle and concavity will do so.
  • Speed — Must be designed for faster tractor travel.

Disc Harrow Requirements

Discs today last longer than discs of 20 years ago and testing is done scientifically. Laboratory tests are made first, and then they are put in all field soils to determine their lasting qualities. Disc blades are heat-treated for long life, and seldom, if at all, will they chip while working. The angling of the gangs must conform to the disc concavity for holding penetration at any depth, and the disc concavity must also match speed at which disc harrows can travel and do quality work.

At the extreme angle the discs cut a clean furrow with no drag on the backside and with no chattering or jumping — that is, they should do so. If not, then there is either too much or too little angling. The concavity also gives the correct curvature in the ground for steady running when set with the least amount of angle. When discs notch the small furrows in washboard fashion working at the minimum angle, it is because the concavity does not follow through with the correct slant against the ground to take a cutting bite. It’s like trying to whittle with a pocketknife set too straight against the wood. With correct concavity, at all angles, and the disc edges set at a pocket knife pitch against the ground for clean cutting, smooth shavings result without jumping and notching the furrows. The correct concavity and angling eliminates the deep furrows.

Disc Harrow Requirements

The disc harrow, like the plow, must have a range of varied depths, or it would be of little value. The disc blade is to the harrow what the plow bottom is to the moldboard plow — it is the business or working end of the tool. Frames, bolts, spools, hitch and proper weight are needed and they do their share to cause good cutting. But the actual cutting, lifting and turning of the dirt is effected by the discs, and to do this work the way the users, soils and conditions require it done, demands discs that have correct concavity, made out of the best material, and then properly heat-treated for a lasting and uninterrupted life. is a live, ever-changing subscription website. To gain access to all the content on this site, subscribe for just $5 per month. If you are not completely satisfied, cancel at any time. Here at your own convenience you can access past articles from Small Farmer's Journal's first forty years and all of the brand new content of new issues. You will also find posts of complete equipment manuals, a wide assortment of valuable ads, a vibrant events calendar, and up to the minute small farm news bulletins. The site features weather forecasts for your own area, moon phase calendaring for farm decisions, recipes, and loads of miscellaneous information.

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