Part five by Jason Ballamy

The lump of ali was starting to look more like an engine crankcase.

With the part held in the vice mounted on top of the rotary table the cylinder mounting flange had some shape added to it.
The rotary table was then mounted vertically and the 3-jaw chucks jaws expanded inside the crankcase opening to hold it. I also turned up a plug to fit the bearing hole so that the R/T tailstock could be used for added support then the case was roughed out to shape.
And then another pass to bring it down to final size.
Then using a ball nose cutter some more excess material was removed.
The R/T was then mounted horizontally again and a start made on machining the stiffening webs at the rear of the crankcase.
The top half was a bit trickier as there is a rounded bulge that follows the line of the cylinder liner cutout, not easily seen in this shot but better in the second where I have made a start at blending some of the machined surfaces with a carbide burr.
It was then just a lot of time with the Dremel and files to refine the shapes. Luckily as the stuart castings are quite textured there was not as much work as there would be doing a diecast crankcase that would be left in bare metal. Here it is with some etch primer.

See Part one here  part two  part three  part foupart five  part six  part seven