The casting includes an extended boss, about 3/4" diameter by 3/4" long, obviously
intended for holding the wheel in the three or four jaw chuck. However, being a rough
casting and including a taper, it needed some work doing on it to make this possible.
I considered filing three of four flats onto it but ultimately chose to mount it
onto the faceplate as seen in Photograph 18. The screws that clamp the wheel to the
faceplate also pass through the packing pieces that can be seen. I chose to do it
this way as should the clamp become loose the packing piece will still be captive.
In addition to the central boss I also machined the outer diameter and the wheel's
face on one side but still leaving a little for final finishing. I then reversed
the wheel on the faceplate, fixing it using the same method, and machined the other
side, concentricity not being vital at this stage.
Next, I mounted the wheel in the three jaw chuck, holding it on the central boss
now turned, and centre drilled the end. Whilst the wheel now only needed lightly
machining on its outer diameter and sides I took the precaution of supporting it
with the tailstock centre whilst these were machined, Photograph 19. With the tailstock
centre removed I then drilled and bored the through hole in the central boss. This
sequence ensured that the bore and outer diameter were concentric but being a large
casting not necessarily balanced. If the engine is to be run under steam then it
would no doubt be worth attempting to improve the balance. Finally, I mounted the
wheel on a taper stub mandrel and carefully machined away the temporary boss.
I mentioned early that I considered that the lathe with milling head should be augmented
by the addition of a small drilling machine rather than attempting to do the drilling
on the lathe also. In keeping with this I have myself also done all the drilling
work on the small drilling machine seen in Photograph 20. This is a five speed machine
with speeds from 500 to 2900rpm and coped with all but one of the tasks required
of it, including the need for a 7/16" diameter hole in the mild steel connecting
rod and initially through 1/2" thick prior to it being reduced in thickness. However,
the hole was drilled initially 1/4" followed by 3/8" and finally 7/16" and was of
course firmly clamped in place for this process. The 500rpm minimum speed was rather
fast for this but the machine coped reasonably well.