mills 1.3cc diesel crankcase model engineering mikes-models

Tuesday 15th January 2008 session 4

Today I started by preparing the defective blank by milling down the underside
of the lugs so I can profile the bottom of the case. To ensure I had the blank
square on I used the angle meter. I then turned the blank upside down and
started to take cuts around the scribed circle following Ron's directions. I did
find that it became easier if I kept the centre punched centre in the same
position above the edge of the vice. Taking small cuts was the best approach
and it seemed to go well enough for me to start on the 'proper' (until I make a
significant mistake!!) blank.

Following Ron's description, I machined the top lugs first, turning the blank
upside down and completing the bottom. I then checked their size against the
plan and they were slightly oversize (I was hoping this would be the case as I
was making allowances to get to the scribed lines) so continued to mill until the
correct size was achieved. I re did the layout blue and re scribed the rear circle
before starting the light cuts, to get the profile around the scribed circle.

I found that on two cuts I did come against the squared front section. On
checking the photo's in the article I was disappointed to see that Ron's
crankcase didn't touch the front so I am hoping I have not done anything
wrong. I have checked and rechecked my measurements and can't at this time
see what's wrong. Since the front squared section is turned down later I am not
going to get too depressed yet! I

I finished by placing the defective blank in the four jaw chuck and using my
home made wobbler [see photo below], got it running true. Ron's tip of using a
tailstock centre to put the blank roughly right worked very well, so I will
remember that tip in the future. So set up I tided up the workshop and
especially the milling machine, ready for the next task of profiling the base of
the engine.

Time spent today 2 hours. Total to date 8 hours.