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 perfectly parallel to the bed of the table so that all surfaces parallel to this can be planed accurately.

A large number of holes have to be drilled in the flanges for the cylinder and steam chest covers, and for uniting the cylinders to the frames. Fig. 22 illustrates a modern machine by Messrs. William Asquith, Halifax, for doing this work. It is also used for facing the front flanges to which the cylinder and steam chest covers are secured.

All joints are carefully faced, and covers fitted on to be perfectly steam-tight. The cylinders should then be tested, preferably by steam pressure, though hydraulic pressure is sometimes used.