The cylinder and valve tube A should be flattened by filing and rubbing on emery cloth, so that they may bed snugly against one another and give a good holding surface for the solder.  A steam port, S P, should next be bored in each, and the “burr” of the edges cleaned off carefully so as not to obstruct valve or piston in the slightest degree.  “Tin” the contact surfaces thinly, and after laying valve tube and cylinder in line, with the portholes corresponding exactly, bind them tightly together with a turn or two of wire, or hold them lightly in a vice, while the solder is made to run again with the aid of a spirit lamp.  If it seems necessary, run a little extra solder along the joint, both sides, and at the ends.

The valve, if built up, consists of a central rod, threaded at the rear end, four washers which fit the tube, and a central spacing-piece.  The forward washer is soldered to the rod.  Behind this is placed a felt packing.  Then come in order the central spacing-piece, with a washer soldered to each end, a second packing, and a fourth washer.  The series is completed by an adjusting nut to squeeze the packings, and a lock nut to prevent slipping.  The back end of the valve must be wide enough to just more than cover the steam port.  If the felt proves difficult to procure or fit, one may use a ring or two of brass tubing, with an external packing of asbestos cord.

The cylinder wing W should have the top edge turned over for an eighth of an inch or so to give a good bearing against the cylinder, and be held in position by a wire while the soldering is done.  It is important that the line of the wing should be at right angles to a line passing through the centres of the valve tube and cylinder.

Shaft Bearings.—­Take a piece of strip brass half an inch or so wide and 3-1/2 inches long.  Bore four holes for screws, and scratch cross lines an inch from each extremity.  Turn up the ends at these lines at right angles to the central part, stand the piece on some flat surface, and on the outer faces of the uprights scratch two cross lines at the height of the centre of the cylinder above the bed.  Mark the central points of these lines.

Next select a piece of brass tubing which fits the rod chosen for the crank shaft, and bore in the bearing standards two holes to fit this tubing.  Slip the tubing through the standards and solder it to them.  The ends and central parts of the tubing must now be so cut away as to leave two bearings, bb—­that at the fly-wheel end projecting far enough to allow the fly wheel, when brought up against it, to just clear the bed; that at the crank end being of the proper length to allow the eccentric to be in line with the valve rod, and the crank disc to occupy its proper position relatively to the central line of the cylinder.  Finish off the standards by filing the tops concentrically with the bearings.