21-05-2021, 05:21 PM
Using EN40B for crankshafts (less memorably called 722M24 in the more recent British Standard) seems to be a UK thing.
With a view to getting a crank made, I was talking to a USA manufacturer of custom crankshafts a couple of years ago; All their products were machined from 4340 material -which we would know as EN24T, that also happens to be the material used to make the billet conrods by Phoenix etc. Having said all that, the nitriding is supposed to increase fatigue strength so I have always gone for Nitrided cranks for the couple of one offs I've had made for old motors until now.
The fatigue strength imparted by nitriding is probably less important on modern engine crankshafts because they always have multiple main bearings and large diameter and narrow (by old motor standards) journals along which along with their short strokes have an inherent high degree of beam strength and torsional rigidity.
With a view to getting a crank made, I was talking to a USA manufacturer of custom crankshafts a couple of years ago; All their products were machined from 4340 material -which we would know as EN24T, that also happens to be the material used to make the billet conrods by Phoenix etc. Having said all that, the nitriding is supposed to increase fatigue strength so I have always gone for Nitrided cranks for the couple of one offs I've had made for old motors until now.
The fatigue strength imparted by nitriding is probably less important on modern engine crankshafts because they always have multiple main bearings and large diameter and narrow (by old motor standards) journals along which along with their short strokes have an inherent high degree of beam strength and torsional rigidity.