mills 1.3cc diesel mikes-models

Crankcase session 17 - 16th March 2008

Its been over a week since I last had chance to do any work on the Mills engine
but today I managed to actually finish this phase of the build! Once I had set the
milling machine up with the small angle plate, I reversed the case and using the
digital angle meter, set it over to 19°. I then found the centre of the case by lining up
the 1/4" long series end mill with the already milled exhaust ports. It was just a case
of taking light cuts until reaching the right position in the lower crankcase. Then set
it over to the other side, and mill the slot again, to allow for the con rod throw.

Next the crankcase was set up to make the threaded hole for the fuel inlet. Ron's
article suggests using a 1/4" by 40tpi (threads per inch) tap so the first action was to
mark its position with the optical centre punch (photo a below). Then over to the
milling machine to centre drill, followed by a number 2 drill. Ron then says to just
break the top of the hole with a 1/4" drill. I took this to mean just take a light cut
sufficient to make the 1/4" drill just cut its size. Something like a chamfer really.

Using my home made tapping guide made out of stainless steel (see photo b) with
one end having a point and the other a recess, which allows it to guide the tap,
depending on type. With some cutting paste it was then a simple task to tap the
hole (photo c) to complete the first phase. More importantly it means the case is
out of danger for the moment, from being turned into scrap. Something I feared the
longer it went on. Well thats the end of the crankcase (photo d) and it only took me
37 hours!

I am sure it would take me a lot less to make another, something maybe for the
future..........