< Smokebox 2 >
The chimney base is made from a cast iron without center hole. At first it is drilled 16mm center hole and inserted a round rod of the same diameter. The rod is aligned with both centers and the casting is chucked in four-jaw, so that the job keeps the same alignment in any time. And then top face and bottom edge are cut. In addition, I cut bottom step of 20mm dia. in order to clamp it in the next operation.
The next is fly-cutting of the round bottom face. As the cutting radius is beyond the lathe center height, the cutter has to spin within 'gap' between the lathe bed and the head stock. The saddle cannot break into the cutting area, too. Therefore the job has to be held far ahead of the saddle. The casting is bolted sideways onto the plate with a 20mm disk (invisible) in the above-mentioned bottom step. The fly cutter is a boring bar held in the tool post chucked in four-jaw.
Again the casting is centered in four-jaw, then the center hole is enlarged to the final diameter, 39mm.
The chimney has a cap made from a cast iron. Only a boring to 39mm dia. is needed.
The chimney base is bolted down to the smokebox with the same manner as the last month's flanged plate assembly.
Smokebox front ring is also made from a cast iron. All faces of the casting are cut in the lathe.
The smokebox has a back ring as well. It is made from a gunmetal casting and finished in the same way.
Return to the flanged plates. Large holes are opened by fret saw and the rings are bolted into them. For front one, the screws come from inside and there is no projection on the ring's surface.
The smokebox door is a cast iron, too. The casting has no hollow. The hollow is cut by 0.25mm steps in depth, so that the door thickness becomes 5mm in the whole area. A center hole is opened here.
Chucking the job as the photo shows, I cut sealing face of the backside.
The door will be fixed firmly onto the front ring with some parts as a crossbar, a dart and two handles.
The dart has round body and triangle head. It is made from a round rod and a flat bar silver-soldered together. Bottom end of the shaft is screwed and followed by a square part that is cut by end mill.
The inner handle bush has screwed hole, while the outer handle bush has square one. The square hole is finished by filing from a drilled hole. The square must fit to the dart closely.
Each handle body has tapered profile. They are turned in the lathe and cut in desired length. The bush is drilled in its side and the handle body is silver soldered in it. Inserted part of the handle should be straight.
The crossbar has a rectangle hole. It is finished by end mill from a line of drilled holes. The paper by the job shows a table of stage coordinates for the cutting.
The smokebox door was temporary fixed on the front ring with the previous parts. It is just the same construction as full size locomotives.