mills 1.3cc diesel crankcase model engineering mikes-models

18th February 2008 session 8.

At last! I can start to focus on building the Mills engine. The hold up in part was due to no
method of holding the 3/4" end mill in the lathe. On reflection I could have bored it out I
suppose but I still think that using the end mill as described by Ron, in his article, is the way to
go. So with my bright new adaptor for M2 to M3 tapers, I fit the end mill to the tailstock. Two
things strike me straight away. Firstly, its a long old thing and not the steadiest method of tool
holding! (see photo 1 below) and secondly, I have no accurate method of judging when the
9/16th depth is reached. Hmmmm....well I am using the practice blank first so I tried by making
an approximate mark on the end mill itself to warn when I was getting near. Stopping the lathe,
moving the tailstock clear then measuring the depth with a digital read out calliper.

Running my lathe at a slow speed I tentatively started the cut. All seemed to be going well ish,
except that the cutter started taking metal only from one edge. I used some cutting oil lubricant
and pushed the whole tool holding as firmly back towards the tailstock as I could. The cutting
oil made a tremendous difference and steady pressure was applied to the cutter which
advanced nicely into the crankcase. I found that the cut was better with frequent withdrawal of
the tool for the application of more cutting oil. However I was still not happy with the length of
the tool holding and its rigidity.

I believe the MT2/MT3 adaptor may well be better used in a milling machine rather than the
lathe. There it would have downward pressure and it would be revolving itself rather than sitting
fixed in the tailstock. Additionally the measurement accurately of the depth of cut led me to
think about using the milling machine itself for the final depth. If I was to use the lathe set up
initially, I could make the final depth cutting accurately if I took the crankcase to the milling
machine. I could locate the position accurately simply by using the hole already cut and placing
the end mill into it. I could then use the digital readout's on the Z axis to get to exactly 9/16th".
My only issue to contend with would be ensuring that the axis was vertical.

I have therefore decided that tomorrow I will try this out using the blank, before using it on the
'proper' crank case. I can always get the crankcase vertical by using a drill in the mill as a guide
when it is in the hole and this would allow me to hold the piece on an angle plate in the correct
90° angle whilst I secure it. Anyway that's what I will try to do. If it works then the whole
process will be done again with the proper crankcase and I can move on.

Time spent today 30 minutes. Total to date 12 hours. 30 minutes.