Components of Power threshers:

i. Concave: – It is a concave shaped metal grating, partly surrounding the cylinder against which the cylinder rubs the grains from the plant or ear heads and through which the grains fall on the sieve.

ii. Cylinder or drum: – It is a balanced rotating assembly, comprising rasp, beater bar or spikes on its periphery and their support for threshing the crop. There are five types of threshing cylinder.

a) Peg tooth cylinder:

• the teeth on the concave and cylinder are so arranged that the cylinder teeth pass midway between the staggered teeth on the concave.
• The concave assembly is pivoted at the rear portion of the machine.
• As the stalks pass through the clearance space, the grains get separated from the head due to impact action between the teeth.

b) Loop type: –

• The cylinder is studded with a number of wire loops throughout its outer periphery.

c) Angle bar cylinder: –

• cylinder is equipped with angle iron bars, helically fitted on the cylinders.
• The bars have rubber pads on their faces.

d) Hammer mill type: –

• the beaters are in the shape of hammer mill.
• The beaters are attached with the beater arm at the tip.
• Beater arms are rigidly fixed to a hub which is mounted on main shaft.

e) Rasp bar cylinder: –

• the cylinder has corrugated bar round it.
• Threshing is accomplished between corrugated cylinder bar and stationary bars of the concave portion.
• The rotating cylinder takes the grains out from the head as it is drawn over the bars on the concave unit.

iii) cleaning units:

• Function of cleaning unit is to separate and clean the threshed grain.
• The cleaning unit mainly consists of two or more oscillating sieves, a fan and an air sucking duct known as Aspirator.
• Primary duct removes major portion of straw, dust and other foreign matter.
• The secondary duct is used for final cleaning of the grains.