Crankshaft Grinding

What is it?

Grinding a crankshaft is the process of removing material from journals in order to recondition and reuse a vital part of an engine. It is usually done during the process of rebuilding an engine when needed. However, there are also some performance aspects which come along with the process.

During an engine rebuild process, it will be determined whether the journal surfaces are within sufficient tolerances to be used as they are or whether they will need to be ground.

Why do it?

  • If the surface of the journal is worn and no longer smooth
  • Or if the journal is out of round or not square
  • To create more stroke

How is it done?

Our specialist machinist will grind part of the top layer of the journal away to make it smooth. Usually, the amount taken off is measured in 0.010″ (usually 0.010″, 0.020″, or 0.030″ – depending on the severity of the wear). Once the journal is ground down close to the final dimensions required, there is then a finishing process of polishing the journals. This involves using a long circular piece of emery paper.

The crankshaft is spun while in the opposite direction and the emery paper is put in contact with the journal. This process creates an ultra smooth surface on the crankshaft. Consequently, this reduces friction and therefore, improves overall power and torque.

To get the crankshaft to work once again in the engine, you have to take up the excess space which is taken away during the process. This is done by using under-sized bearings. The bearings are matched to maintain the proper clearances for oil flow at the new diameter of the journal.

The main reason for grinding a crankshaft is as stated above. However, there are some additional benefits to doing the grinding, which are listed below.

 – It lightens the overall weight of the crankshaft.

 – It reduces the journals size, therefore reducing the surface area.  This means the surface area reduces friction losses imposed by the journal faces, creating greater efficiencies and thus making more power/torque.

 – The grinding process also makes the corner of the journals so they have a greater radius. This makes the crankshaft stronger by reducing the stress riser at the corners.

Contact us for more information!

Cleasby Engine Services - Crankshaft Grinding