Those who own performance engines, and want to gain the most horsepower possible, often seek the services of an automotive machine shop that provides a crankshaft knife edging service. Normally reserved for racing applications, a knife edged crankshaft can help the engine produce more horsepower. Below we will look at how the knife edging process is completed and the benefits it offers.
As you can tell by the picture to your left, a knife edged crankshaft refers to the shape of the crankshaft’s counterweights. Removing this material and bringing it to a sharp edge does a couple of things. First, knife edging can often remove pounds of weight from a V8 crankshaft. Even some V6 crankshafts will realize a significant weight reduction when the counterweights have been knife edged. Less weight equates to a rotating assembly that spins with less resistance, and this in itself is responsible for some gains in horsepower. Knife edging also reduces friction, which is explained below.
The counterweights on most crankshafts are flat on the ends. As the crankshaft rotates, these counterweights come into direct contact with the engine’s oil. This contact creates friction and splashes oil all over the bottom end of the engine. A knifed edged crankshaft actually glides through the oil much easier and encounters far less friction. Anytime friction can be reduced in an engine’s rotating assembly or valvetrain, additional horsepower gains are realized.
There are many automotive machine shops that provide crankshaft knife edging services. However, how these shops perform the machining process does vary. Most machine shops will use a Bridgeport milling machine to rough in the counterweights, whereas some shops will simply grind the counterweights to a point. Regardless of which technique is used to perform the knife edge service, there are some steps that the machinist must take to protect the crankshaft prior to the machining operation.
Ideally, it is best to knife edge a crankshaft before any finish machining operations are performed. For example, if the crank needs to be ground or polished, these processes should be performed after the knife edging tasks are completed. The reason for this is that there is the potential for a grinding stone or tool to slip and come into contact with a journal. Although rare, particularly among experienced machinists who have knife edged many crankshafts, it is best to err on the side of caution.
Because of the material being removed from the crankshaft’s counterweights during a knife edging process, the rotating assembly will need to be balanced when the crankshaft is finished. Often lighter rods or pistons can help compensate for the crankshaft’s reduced weight. By properly planning for the reduced weight of a knife edged crankshaft, these variables can be considered first so that the need for heavy metal during balancing is greatly reduced.
Now that you have learned more about how the knife edging process can help to reduce a crankshaft’s weight and friction, please consider rating this page below so that we can further improve upon the information that we present to our valued visitors.