Honing of the connecting rod bores Connecting rod. For connecting rods too, STIHL divides between forged and stamped con-rods, depending on specific requirements. The forged con-rods, which have to provide higher performance, are drilled, the faces are ground and finally the bore holes are honed; that means the bore-holes are subjected to extreme tight tolerances. It is especially important in this process that the distance between the two holes for the stroke and piston pin complies to tight tolerances to ensure optimum running characteristics and engine performance.

Connecting rod? Sounds like something for long-distance communication to me. What is a connecting rod? The connecting rod is the thrusting arm of the piston. The function of the connecting rod is to convert the up-and-down movement of the piston into the rotary movement of the crankshaft. The quality of the connecting rod depends on precise processing. How do you stay process capable within the tolerances? Special rough machining equipment, which already takes dimensional changes in heat treatment into account, ensures that the tolerances for the distance between the 2 holes are maintained. The final correction is made during the honing process. With so many different demands, I assume that there must be more than just one type of connecting rod? Exactly, at STIHL there are two different families. For professional saws and powertools with tough work requirements we use forged connecting rods with higher tensile strength. I have heard that connecting rods also have an impact on emissions. Is that right? Yes, the center distance between stroke and piston pin affects the engine compression and therefore running properties and emissions characteristics.