Components of a Crankshaft

• Main Journals
• Rod Journals
• Snout/Nose
• Flywheel Mounting Flange
• Throws
• Counterweights
• Web

Crankshaft Grinding: The main parts we are working with when grinding are the main & rod journals. In the midst of the engine rebuild it will be determined if the journal surfaces are within sufficient tolerances to be reused as is or if they will need to be ground. If the crankshaft can be reused but machining will be necessary in order for it to work, the crank's top layer will be ground to make it smooth again. Depending on the severity of the wear, the amount taken off is usually measured by 0.010", 0.020", or 0.030" and so on.

Here are some of the many reasons why they may need to be machined:

• Surface of the journal has wear which makes it no longer smooth.
• If the journal is out of round.
• If the journal is not square (same diameter at both ends of the pin).
• Can also be ground to produce more stroke.

Crankshaft Polishing: The process of polishing finishes the journals after being ground to the final measurements. This involves using using a long circular piece of emery paper. Polishing creates an extremely smooth surface which reduces friction and improves overall power and torque.

Crankshaft Bearings: Excess space which is taken away during the grinding process needs to be filled by using under-sized bearings. The bearings are matched to maintain the proper clearances for oil flow at the new diameter of the journal.

1. Lightens the overall weight of the crankshaft, but does not do so much to create a huge difference. If you wanted to reduce weight, you will do things like drill the pins.
2. By reducing the size of the journals, you have less surface area. Reducing the surface area reduces friction losses imposed by the journal faces. The difference is measurable on an engine dyno. If you are an engine builder doing a max effort, this is definitely one area to look at for creating greater efficiencies and thus making more power & torque especially for a performance build.
3. The grinding process also makes the corner of the journals have a greater radius. This actually makes the crankshaft stronger by reducing the stress riser on those corners.