When forming metal into a curved shape, metal fabricators must always allow for the centre measurement of the metal remaining constant. This is called the neutral axis. The outside surface stretches and the inside surface contracts.
The neutral axis is better known as the mean diameter (MD).
Mean diameter = inside diameter + one plate thickness (of the material used)
MD = ID + T
Mean diameter = outside diameter - one plate thickness
MD = OD -T
The mean circumference (MC) is also the cutting length. Use the formula:
MC = MD x . ( = 3.142).
What length of 10mm mild steel plate is needed to form a cylinder having an outside diameter (OD) of 650mm?
Calculate the mean diameter
MD = OD - T
= 650 - 10
Calculate the mean circumference
MC = MD x =
= 640 x 3.142
= 2011mm (rounded off to the nearest mm)
The following diagram shows the cutting length (mean circumference) of the material.
Therefore a piece of 10mm mild steel plate, 2011mm long is required to roll up to an outside diameter (OD) of 650mm and inside diameter (ID) of 630mm.