Agriculture Sickle Sections Explained
Smooth = no teeth per inch [PI]
STD = 14 serrations per inch [PI]
BT = Big Tooth 10 serrations per inch [PI]
LS = Large or Saber Tooth 7 serrations per inch [PI]
Definition:
Under serrated vs top serrated: The knife or sickle sections may have grooves along the cutting edges, these are known as serrations. When these serrations face upward, the knife is often called over serrated or top serrated. If the grooves are on the bottom, it is called under serrated or bottom serrated.
TOP-SERRATED, UNDER-SERRATED OR SMOOTH
New Holland coined top-serrated design, it controls the movement of abrasive material, creating visible wear lines from the serrations on one cutting edge to corresponding serrations on the opposite cutting edge (see inset). By diverting much of the wear from the points of the teeth to the bottoms of the “V”, teeth retain shape and sharpness even though the section has worn farther than the depth of the original serrations. Under-serrated sections must be hand-sharpened to retain their original profile. Smooth sections are the old standby for fine, grassy and wiry conditions.
BLACK OR ZINC PLATING
Black versus zinc plating — which is best? Both are good, and both are available, but the performance gap between the two is growing smaller. Originally, superior durability gave the zinc plated section a marked advantage in abrasive soil, despite its higher price. Today, that advantage still exists, but the self-sharpening, reshaping action of the coined top-serrated design has added many hours and acres of useful life to the black section, making it the better value under a wider range of conditions.
STANDARD, COARSE [BT] OR T-REX [LS] SERRATIONS
There’s a place for each type. Coarse serrated sections have grown in popularity for certain field conditions. With 7- or 10-deep serrations per inch, instead of 14, coarse serrated sections especially efficient for harvesting coarse, dry-stemmed crops. However, the standard (14-per-inch serrations) sections are more versatile and the better choice for most conditions.
Ref: PM-16916-NH-2014-Hay-Machines-Product-Support-Kits-Catalog.pdf