If you are making the 10H you may find the flywheel touching the boxbed when assembled
as I did if working to the dimensions given. Of course, this could be as a result
of an accumulation of very small errors all working against me. I obtained clearance
by moving the flywheel fully to the end of the crankshaft and using the clearance
in the fixing holes for the crankshaft bearings and the soleplate to move the flywheel
sideways. I would because of this suggest making that end of the crankshaft say 1/32”
Having now completed the crankshaft, it, together with the crankshaft bearings, can
be used to position the final holes in the soleplate, see Photograph 67. As the holes
in the bearings are clearance size just spot through and then remove and drill the
casting 2.1mm for tapping 7BA.
Cylinder Lagging 1
This is made from 0.020” thick black anodised aluminium and requires 5 holes and
2 small slots to be made making it a tricky task as one of the holes is 1/4” diameter.
However, if you have chosen to make it a display model only, at least initially,
then the 1/4” hole can be omitted. Similarly, two of the holes (no size given)
are for fitting drain cocks, therefore, if you do not intend to fit these then these
can be omitted also. More important is that one side of the black anodised finish
is seen in the final assembly and should not therefore be damaged. Marking it out
on the reverse side and centre punching and drilling from that side is a possibility
but fraught with problems. The best solution is therefore to make a simple drilling
Using a piece of sheet steel or mild steel strip (at least 2mm thick) cut two pieces
1-1/8” by 3-25/32” and mark out and drill one plate as per the drawing. The drawing
though calls for two slots 3/32” wide by 3/16” long, for these use two 3/32” holes
in the template per slot and finish the slots by filing in the lagging itself.
To drill the holes, place the part between the two plates, clamp together, and drill,
Photograph 68, using a piece of paper between the top plate and the part to protect
the finish. This is a typical example of how single sided toolmakers clamps can be
very useful on the drilling machine.
No doubt there will be a few holes yet to be drilled and hopefully (as it makes sense)
the majority of the 7BA tapped holes are still to be tapped. If you do not posses
a tapping stand that will enable holes to be made perfectly upright than make a simple
guide and use this where practical, see photograph 58. For my part, I used my controlled
feed tapping stand that automatically feeds the tap at the correct rate for the pitch
being tapped, Photograph 69. Details of this are given elsewhere on the site.
Set screw (46)
One of the screws provided requires modifying, following being a possible method.
Take a small piece of 3/32” thick steel, size not important but say 1” x 1”, and
drill and tap it centrally 7BA and countersink slightly to enable the screw to be
threaded fully into this.
Then, using the three jaw chuck, place some thin film double adhesive onto the ends
of the jaws and place the assembly into the chuck very lightly gripping the hexagon
head of screw. Now apply pressure using the tailstock and lightly tighten the chuck
onto the screw's head. With the lathe running at maximum speed carefully turn the
1/16” diameter leaving it at the length of the original screw and reducing it as
found necessary at the assembly stage, doing this with a file at that time will be
more than adequate.