< Smokebox 5 >
Let's start with the chimney casting. The casting is centered roughly and chucked in the four-jaw. Finish the top face and bore to 40 mm dia., so as to be aligned with the 40 mm dia. mandrel.
Align the chimney on the mandrel by both centers and tighten the four-jaw. Each jaw has to be tightened with equal force, otherwise the center is shifted. After that, finish the outer face of the top part, remove only the mandrel, and finish the inner taper face.
Reverse and chuck truly in the same way. Cut threads in the outer face of the bottom part by a threading tool.
Completed chimney.
Next is the chimney base. It is also bored to 40 mm dia. to utilize the mandrel. Reverse and align center with the mandrel, remove the mandrel and cut an inner step to catch a disc in the next process. Here the outer edge of the saddle is also finished.
Hold the base on a vertical plate with a disc. Fly-cut the bottom face of the saddle. The fly cutter is a boring bar in the tool post chucked in the four-jaw.
Align the center again and finish the bore. Note the cast skin in the top face of the saddle remains.
The chimney and the chimney base are silver soldered.
Chuck the whole job with the mandrel in the four-jaw. Turn the neck of the chimney base. Stop the rotation and finish the saddle surface by hand with files.
Insert the chimney in the smokebox and drill holes for screws and nuts. The purpose is not to fix the chimney but to make detail.
The next is the petticoat pipe screwed in under the chimney. First, clean the bottom and bore to 40 mm dia. Reverse and align center with the mandrel. Finish and part of a ring that will be fixed in the smokebox. The ring will be machined later.
The inside of the petticoat pipe is threaded. Before that, a groove to let the threading tool escape is turned by the internal grooving tool that I introduced last month.
Reverse and align center with the mandrel. Finish the inside and outside of the petticoat part. For the inside curved face, I turned many 0.1 mm steps and finished with a file. Now the petticoat pipe is finished.
The last is the parted ring. It has a round face in order to fix to the inside of the smokebox. Stand the ring vertically on the outer part of the face plate with an angle plate and a disc. And then, turn the outer face. The brass disc is not visible in the photo. Finally, finish the inner diameter and the ring is completed.
The ring is fixed in the smokebox with two screws and the petticoat pipe is screwed into the chimney bottom. The ring is between the smokebox inside face and petticoat and it closes the gap between them.
The smokebox exterior is completed. The inside parts will be made after mounting the boiler.
