mills 1.3cc diesel mikes-models model engineering

5th March 2008 session 15a

Well following an email to Ron Chernich I decided to give the milling of the
crankcase a go. I spent 45 minutes setting the crankcase up on the angle
plate [photo a] using an electronic edge finder [photo b] This ensured the
case was level in all planes (sorry about the pun!). Ron stresses that you
must be careful when breaking through with the drill, so as not to drill into
the datum plug. So I was particularly careful with the drilling and decided I
could indeed be a bit clever here…..so to prove how clever I am, I drilled
into the plug!

I found setting up the crankcase for milling, whilst time consuming, didn’t
cause many problems. I decided also to pack out underneath the
crankcase in case any tendency to push down occurred when first drilling.
A bit belts and braces really…so how did I go wrong and drill the datum
plug? Well I thought it would be quite clever to drill down so far with the
first small drill, before opening up the hole with increasingly bigger drills. I
then changed to the next drill size up and drilled down to the same depth,
guided by my digital readout. I thought that if I then reverted back to the
smaller drill, I could fill the resulting hole with cutting fluid and as I broke
through, the fluid would drain, and I could then set the digital readout to
zero, thereby making it safe for all other drills and the boring bar.

This plan seemed to work and I was pleased when the hole drained. For
some reason (called stupidity!) I looked into the hole with an angled mirror
to check that all was well and saw that I had broken through, so instead of
setting the readout to zero, I continued to drill down! Why? Just
mindlessness! I instantly knew that I had gone too far, and the realisation
that I had made a big mistake dawned heavily on me……however, when
looking again into the drilled hole I couldn’t be sure whether I had
damaged the plug or no, but how could I tell without disturbing the
crankcase?

It took a while, thinking what I could do, but without an endoscope there
was no way out of it. The crankcase would have to come off, loosing all
my settings into the bargain! However, I hadn’t got past the stage whereby
all would be lost, although it would be a pain in the Ł$%. So oft it jolly well
came. And sure enough, my worst fears were realised. I had drilled into the
steel plug [photo c]. Now what? I would have to make a new plug and that
would really be a problem, one that I didn’t rally want. I went and made a
cup of tea and had another think. The plug was there so I could measure
the amount of material to skim off the top. As Ron so ably explained in his
email to me, this was a critical measurement, and a couple of thou out,
would mean a big, big difference in the engines starting and running.

Then it came to me that if I filled the hole flush, that would be ok. I had
some ‘plastic metal’ a two part mix. If I filled the hole and left it overnight
to cure than with careful sanding, I should be able to recover the situation,
as long as it is flush. So I mixed up a little of the filler and left it to cure
overnight [photo 26], so it should be ready for the next session. I will test
the results with a dial gauge just to be sure it is acceptable. If not, it’s
another plug to make. Not a disaster, but it stopped me finishing this part of
the job today. So all in all, not a good day…..So I started on making the
switch box for the Myford refurbishment ..............

Time spent today 1 hour 30 minutes. Total to date 32 hours.