Checking the progress of the lapping of the mounting end of the cylinder. Both of the pieces being lapped were faced by the Cass machinist to remove the radial steam-cut grooves in all the components. The cylinder head has a raised "land" about one inch wide that defines where the mating up is to occur. The only portion of the head to contact the cylinder is this "land". If the entire head and cylinder face were to touch, the bolts could not create enough pounds per square inch surface pressure to prevent the joint from leaking massive clouds of steam.

Photo by Bill Liebman