mills 1.3cc diesel mikes-models

8th March 2008 session 16

Today started by sanding off the plastic 'metal' flush with the datum, plug and
fortunately it sanded well and flush. I used the dial indicator [photo a]to make sure
it was level and so it proved to be....so I got away it! Once this was completed I
went through the set up procedure to make sure it was level on all planes. Trying
to make sure that I learnt my lesson and not to repeat my error I decided to put a
little 'reminder' on the mill at eye level[ photo b]! It was then a case of increasing
drill sizes to get the hole to a sufficient size to bring the boring bar into use.

I managed to take light cuts and repeated measurements until the 0.5000" bore
was completed. The digital readouts fitted to my milling machine are worth the
weight in gold and I cannot praise them highly enough. The ability to move the bed
and to reposition it to 4 decimal places is confidence building. I wouldn't be
without them and if I keep the ML7 I will certainly save my pennies to buy a set
for that lathe as well.

Back to the crankcase, after completing the boring and running it through a couple
of times, the next job to do required considerable accuracy according to Ron. The
height of the top surface in relation to the crankshaft access is critical because any
inaccuracy will affect the timing. Leading to reduced performance and poor
starting. Armed with this information I was very nervous and worked through the
problem 'several' times! You have to take the measurement of the diameter of the
plug (D) and then the diameter across the plug ,where it has been milled down (X)
(all done before I started) . Ron's formulae is that the datum height you are looking
for = X - (D/2) and this is then recorded as the datum height. Having now
calculated the datum height it is possible to mill the top to the correct dimensions.

This is where I lost about 40 minutes of my life! I measured the depth of the hole
and looked at the dimensions in Ron's accompanying article after the first light cut
and found I was about a 1/4" out!!!!! I repeated the process and came to the
same conclusion. It didn't make sense, though I still felt sick at producing and
elegant piece of scrap. To cut a long story short, I needed to go back in the article
and remembered at last the need to add the datum height to the measurements in
hand. I even went back through the basic marking out plans, going through all the
calculations. Anyhow all was well in the end.

The next task was to cut the exhaust outlets [photo 29] and finished the day by
using the 0.25" long series end mill to cut the 0.95" long indent in the front face,
ending up with the crankcase as shown below.

The next tasks will be to reverse the crankcase and set it over 19° and mill two
slots. After which we will be close to starting on another piece of the engine and
out of the woods for mucking it up. So concentration will need to be even higher
because its near the end.

It makes me smile (I think that's what I mean...) to think of the many many hours it
is taking me to do a job which Ron no doubt did in a couple! But we all have to
learn and I suppose time should be allowed for not only setting up, doing the
machining, but also taking the photo's and re reading the plans and article . It
would be interesting to make another in the future and compare my times. It would
have to be at the bottom of the projects list though as I need to stretch my
boundaries........

Time spent today 3 hour 30 minutes. Total to date 35 hours 30 minutes.