Having set the cylinders up the first check made was that both castings were sitting flat on the ‘table’. This was done between each casting and the ‘table’ top using a feeler gauge which was 0.002” thick – i.e. two-thousandths of an inch.
These photos show the joint between the cylinders secured with temporary bolts. In the centre is the hand tool made to skim the casting surfaces around each bolt hole to ensure that the fitted bolt heads and nuts when inserted can be tightened evenly onto the casting surfaces.
A further alignment check was made using a straight edge across the cylinder end faces and the edges of the cylinder flanges. The straight edge is an 8 feet long steel bar which has been ground true over its length which is kept solely for this sort of work. This check was also done using feeler gauges to ensure there were no unacceptable gaps compared with the GWR standard tolerances for machined parts.
Having prepared the two cylinder castings they were separated for the joint faces to be cleaned up ready for the application of the jointing compound. The photo shows the area involved.
This photo shows one of the cylinder faces liberally coated with the jointing compound.
The two castings were rejoined on the ‘table’ and the same alignment checks made to confirm all was well before the bolts were tightened. The photo shows the cylinder flanges with bolts in place and evidence that the jointing compound has squeezed all around the joint
First published on the WSRA 4561 restoration blog.