mills 1.3cc diesel crankcase model engineering mikes-models

19th February 2008 session 9

Well today was certainly a learning experience! Got the angle for setting the topside over
for internal screw cutting completely wrong! Failed to cut the cavity with the 3/4" end mill
with any sort of success and finally, if this had been the 'proper' crankcase it would have
been successfully turned into scrap! So those were the positives......What I did achieve
however was to realise something was wrong with the screw cutting and saved my sanity
for another day. All of which certainly adds to my 'experience' as a novice model engineer
and that is what it is all about is it not.

So I started firstly by trying to set up the crankcase to use the 3/4" end mill in a different
way to Ron Chernich. Guess what, he has the best methods! I did not feel that the
accuracy I could get by moving between the lathe, the mill and back to the lathe again
would work. So I reset the practice blank back in the 4 jaw chuck and decided I would
bore out the remaining width and depth instead of continuing with the end mill in the
monstrous MT2/MT3 extension. I could see the adaptor being useful in a milling situation
but I feel that in the lathe its length would not allow the accuracy I think is needed. More
experienced engineers may well put me right on this......anyway I decided to bite the bullet
and get a MT2 collet holder after all. I will need to use this facility many times I would
guess in the future. I have a set of ER25 collets recently purchased so getting an MT2
holder makes sense. Its just that I am tight sometimes and in this instance that has caused
me to spend more!

Boring out the cavity to the required dimensions went well. It took a little while to sort out
what was required for the deeper recess further inside the crankcase, referring often to the
plans as well as Ron's description. This time was not down to a lack of clarity on Ron's
part, more to my concentration level's. Anyway I got there in the end and achieved the
correct dimensions for the cavity( see photo 1 on the right) but only after changing boring
tools. The first one would not give enough clearance for the recess so I changed it for a
better tool (photo2 on the right) and thereafter had no problems.

After reaming the shaft hole I could no longer delay the dreaded internal screw cutting for
the back plate. So checking again (and again!) the required angle to set the top slide over
to (29.5°) I went to unlock the top slide but it wouldn't move! I thought I was being clever
by fitting the digital readout on to the top slide. Indeed it worked very well earlier. but my
method of securing it would not allow the top slide to move. So it had to come off (and I
will have to have a rethink when it comes time to refit it). Anyhow whilst I could see the
threads starting to form they did not appear to be getting deeper and I was more than a
little disappointed (photo 3 on the left). So what if anything had gone wrong? I would have
to re-read the books on screw cutting. I also had a look at the photo's in the magazine
article and Ron's certainly looked better!. Its just a good job I decided to keep going with
the defective blank. Something I think I will do again with the next suitable project.

So quite an eventful morning really. On retiring to the bungalow armed with various books
and my Jose F. Rodriguez video's, (worth their weight in gold to the novice! - click here
for link to buy, ). Well I know where I went wrong now. I thought that since my top slide
sits on a graduated scale marked in degree's I needed to set it to 29.5. But no, the angle
relates to the top slide setting against the cross slide. Having the top slide set as I did I was
not increasing the depth of the screw as I was pushing it across the x axis....... so now I
know. I think I will have another go on a blank piece of aluminium and not the crankcase
yet. I feel I need to get this right first as it is a very important area to ensure the engine
runs!

Quite an eventful morning as I said. I am not disappointed as there were many good
learning points and no major damage!

Time spent today 3 hours 30 minutes. Total to date 16 hours. 00 minutes.