When it comes to repairing a crankshaft, there is a certain sequence of processes that must be followed. Once the crankshaft has been cleaned and checked for straightness, any significant runout (bend) in the crankshaft must be corrected with a straightening process. There are two primary techniques used for straightening, which are described below.
Hydraulic Press Straightening
Many automotive machine shops use a hydraulic press (pictured left) to straighten crankshafts. This is accomplished by placing the crankshaft in v blocks and applying pressure on the crankshaft journal, on the opposite side of the bend, to essentially bend the crankshaft back into its normal position. This process can be more difficult on cast steel crankshafts as they are more likely to crack under pressure. To avoid the potential of cracking, some shops apply heat to the center main journal to help it relax so that it goes back into its natural position with less force. 4340 forged steel crankshafts, for example, are less likely to break when using a hydraulic press to correct the bend since this type of steel is much softer than cast steel. Continue reading