LO 7-7 Identify and explain the purpose, function, and construction features of connecting rods

LO 7-07: Identify and explain the purpose, function, and construction features of connecting rods.

Connecting Rod Materials

Because connecting rods are highly stressed, they are commonly forged from high-alloy steel. Rods are then shot-peened to relieve stress risers (points where the rod can easily break) and add additional fatigue strength. This technique involves shooting thousands of small steel balls at the rod using compressed air. The balls make small dents in the rod surface and smooth, or peen, over any microscopic cracks or pores in the rod that could form stress risers. Bolts used on the caps are made from proprietary alloys of grade 8 or higher metals. Rolled threads are used on these bolts to increase their strength Figure 47. Rolled threads have a wider root diameter and are pressed into the bolt, not machine cut. The machine cut of a die making threads leaves stress risers. Rolling threads does not remove metal or disturb the metal’s grain structure. Bolts with rolled threads can withstand more stretching or preload than machine-cut threads.

FIGURE 07-1: TEXT

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