July 8, 2008

July & August will be active months of machining for 786's cylinder castings.  The bottom of the cylinders has been machined to fit on the frame.  A special machining fixture has been made to hold the cylinders in position for machining on the big horizontal boring mill.  The cylinders are mounted on the fixture and aligned with the mill.

The next machining step is to cut the 3.5 foot radius that forms the base for the bottom of the boiler's smoke box. 

By the time the cylinder castings have been completely machined and mounted on the frame, approximately 4,000 pounds of chips will have been removed!

Ronnie Jones is turning the cylinder casting to sit on the  machining fixture	Photo: Steam Operations Corporation
Machining fixture in the foreground	Photo: Steam Operations Corporation
The fixture replicates the mounting dimensions of the frame and will serve as the starting point for all future  machine operations.	Photo: Steam Operations Corporation
The cylinder mounted on the fixture in front of the large horizontal boring mill.	Photo: Steam Operations Corporation
In preparation for milling the saddle (shown below), Ronnie Jones and Craig Bauer are using a dial indicator, mounted in the mill's arbor to accurately align the cylinder castings to the machining axes of the mill.  This cylinder bore had been previously machined (not to the final diameter) to provide an accurate reference surface for this step.	Photo: Steam Operations Corporation
Overview of Horizontal Boring Mill with cylinders set up for machining.	Photo: Steam Operations Corporation
CAD layout of the cylinders	Photo: Steam Operations Corporation
Digital readout with machining parameters for saddle.	Photo: Steam Operations Corporation
Preparing for the first pass of the cutter for machining the cylinder saddle.	Photo: Steam Operations Corporation
First pass of tooling over cylinder saddle. The cylinder saddle is the point where the smoke box sits and is secured to the saddle.	Photo: Steam Operations Corporation
Machining the cylinder saddle:  The milling machine is programmed to follow the proper radius of the saddle (about 42") and the arbor (that holds the cutting tool) advances forward with each pass. The machine cut is 3/4" deep and  advances 0.150" each pass.  (A little more than 1/8") Lots of chips!	Photo: Steam Operations Corporation
The cutter will make multiple passes until the saddle is the correct height above the centerline of the cylinders.	Photo: Steam Operations Corporation