More progress in the Workshop

More work has been going into the batch of Quarry Hunslets.  Last time I prepared the bar stock to make the cylinder blocks.  This time more of the same.  The first operation is to machine the middle of the block away to form the valve face.

Using the table stops on the mill makes machining the valve face quick work.

This is recessed so that the valve chest sits under the smoke box of the engine. Then narrow grooves are milled across the width of the block, these are to take 1/16" wide keys that retain and lock the block into the frames.  They also provide a useful point to index the block when machining the locations for the cylinders themselves.  Again the face of the machine vice provides the datum, material in the slot  providing a useful stop.  In this way all the blocks end the same size and the cylinders are parallel and the same distance from the face of the frames.  All done without measuring just using a centre finder, the machine vice face  and the stops on the machine.
The next stage is bench work with a small drill press and a pendant drill. This is the bit where a mistake is starting to be costly. First the centre line have to be lightly marked on the valve face.

Having machined the valve face the tool marks have to abraded away without the flatness being lost.

Then the hardened drilling jig is clamped on, sighting the scribed lines through the holes in the jig.  Then the ports are drilled through.  I have found that round ports work perfectly well and drilling them all the same size does not adversley affect the running of the engine.

Using the jig to drill the ports.

Then all the steam ways have to be drilled into the block  and sockets formed to take the inlet and exhaust steam couplings. Connecting the exhaust to the central exhaust ports is the bit I like least since it has to be done by eye using a pendant drill.  If you miss the port  you can write off the block.  The drill press is used to drill from the cylinder face to the inlet ports , it is a deep hole and can wander if the chips are not cleared.

All the steam ways drilled, next make the cylinders.The valve face is offset to one side to give room for the exhaust pipe.