Question

Which types of knife sections are used in a standard cutter bar
(A). Top serrated type
(B). Under serrated type
(C). Smooth edge type
Choose the correct answer from the options given below:

• A. (A) only
• B. (A) and (B) only
• C. (A) and (C) only
• D. (A), (B) and (C)

Hint:

For harvesting grain crops like wheat and paddy, top-serrated knife sections are preferred because they retain their cutting performance even when dull.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A standard cutter bar on mowers, reapers, and combines cuts crop stems using a shearing action between moving knife sections and stationary guard ledger plates.
The edges of the reciprocating knife sections are designed differently depending on the mechanical characteristics of the crop stems being harvested.

Step 2: Detailed Explanation:
Cutter bars utilize three primary types of knife sections:
1.Smooth Edge Sections (C): These have smooth, sharpened cutting edges.
They work best for cutting grasses, forage, and crops with wet or fleshy stems because they make a clean, low-resistance slice.
They require frequent sharpening but are easy to maintain.
2.Top Serrated Sections (A): These feature serrations or teeth cut into the upper bevelled surface of the blade.
The serrations act like a small saw, holding dry, fibrous, or slippery crop stems (such as straw, wheat, and paddy) in place against the ledger plate while cutting.
These do not require frequent sharpening because the teeth wear down evenly.
3.Under Serrated Sections (B): These have serrations cut on the underside of the cutting bevel, offering a similar gripping action to top-serrated sections but with different wear characteristics.
Because all three types are standard, commercially available knife sections, they are all widely utilized based on crop conditions.

Step 3: Final Answer:
All three types of knife sections—top-serrated, under-serrated, and smooth edge—are standard designs.