mills 1.3cc diesel mikes-models

Session 1 17th March 2008

Having at long last completed the crankcase I have at last started on
something new! Yesterday, after completing the crankcase I had a couple
of practice goes at cutting threads ready for the back-plate. I found it hard
going but that was more to do with me than the task. However today it did
prove of benefit.

To date I have religiously followed Ron's narrative in his article. However,
last night I decided I would change Ron's method. I decided rather than
cut the required thread length exactly to size as Ron suggests, but to cut
the thread to the right diameter over a greater length, then face it back to
size. I also reduced the lathes speed, by moving the belt drive to a slower
basic speed even though it is variable. These two changes made it a lot
easier for me as I then only had to concentrate on getting the thread
diameter correct for the crankcase.

Once I got the fit right (constantly checking after each cut!) I was pleased
that the back-plate sat up against the crankcase without welding itself
together, something Ron warns you of!

The next stage is to turn the back-plate around and protecting the threads
(Ron suggest using aluminium for scrap beer cans….something I don't use
unfortunately) with some hard foam (photo a) I could face it back to size
before centre drilling and opening out the recess with the boring bar.
A tool is required to lock and open the back-plate when fitted to the
crankcase. This is simply a piece of steel turned to fit the recess in the
back-plate. I decided that I would knurl the edge (photo b) as this is
something I do little of and it should look nicer as well as being easier to
grip when in use.

That's as far as I got this session and only have to drill and fit brass
pins…more of that in the next, and I suspect final session for this part. The
three objects I now have are shown in photo c below.

Whilst the threaded back-plate works and locks up (finger tight only until
the special tool is completed) I am not really happy with the threaded
parts. The initial location when entering the crankcase could be better. I
am hoping that is the back-plate threads rather than the crankcase are the
ones that could be improved. It certainly works at present but I may have
a go at making another to see if it would be any different, if not then the
one made today would work I am sure.

Time taken so far on this part 2hours 30 minutes.
Total time 39 hours and 30 minutes.

Session 2 22nd March 2008

Today I finished making the knurled locking tool for the backplate. Ron, in
his article, allowed for a bar to go through it to tighten the backplate fully. I
may have to resort to the same, but for now I decided to leave it as it was
and then cut the two brass pins to fit the drilled holes as per plan.

Looking then at the threaded backplate previously made I was
disappointed with the threads, so decided to make another. The second
attempt took far less time, with no constant referral to my notes and article
and in the end I was quite pleased with the result. The threads on this one
have a far better definition and more importantly, a better fit into the rear
of the crankcase.

It was just left to glue the brass pins into the knurled locking tool. With this
done the backplate is now completed until the final clean up and polish.

Time taken so far on this part 3hours 30 minutes.
Total time40 hours and 30 minutes.