Hello guys,
About six months ago, I ordered a Ministeam 1/4 scale Olds hit& miss casting kit. I'm taking it very slow, learning the lathe, learning
the mill as I go. And buying the necessary tools as I need them. So far I'm having a lot of fun with it. Making mistakes, fixing them.
One of the more difficult parts that had me puzzled how to go about it, was the drilling of the bore where the cylinder sleeve gets to sit.
Searched a lot on internet, but never got a good answer. So in the end I ordered a boring head for the mill. The longest cutter that came
with it was not long enough to reach also the back side of the bore. Luckily I had some cheap amazon boring bars laying around, with
carbide inserts, that I had bought together with the lathe. It's a mistake all of us make I guess. I have now wisened up and bought proper
cutters and holders for the lathe and the mill. But anyway I adapted one of the cheap boring bars on the lathe to fit in the boring head,
and managed to get just enough reach.
To clamp the engine on the mill, I used a 90 degree angle. The official machinist clamp set couldn't be used for various reasons, so in the
end I clamped it down to the angle with two ordinary c-clamps. Measured everything out so all was in line with the table and went ahead.
See the boring video below.
It went fine. The surface finish is very good, at both ends of the bore. But as I had finished up, cleaned the chips and removed the engine
from the table, I found out I had made oval holes. The top to bottom dimension of the hole (the one I was constantly measuring as I was boring)
was dead on. But the left to right (left side of the engine, right side of the engine) dimension was about 0,1 mm smaller. Also at both ends of the engine.
And I can't figure out why that is. I imagine there must have been lack of rigidity (although I clamped down pretty tight and it all seemed very solid) but why the left to right dimension being smaller ? I would imagine I had less rigidity in the left to right direction. Does that make sense ?....
No idea what caused this. Also it's not a big problem, because these holes just accommodate the steel cylinder sleeve, and since it needs to be sealed for the water cooling, some rtv will fill up that 0.1 mm no problem.
But if anyone has any bright light to shine on this I would really like to learn from it
Any help very much appreciated !
Hans
(Post edited because I had a brain fart and messed up the direction of the oval hole. In conclusion, if I measure the bore with the engine sitting on the desk, the dimension from top to bottom of the hole is 0.1 mm bigger than when measured from left to right. And this happens at the front of the engine where the cylinder head is going to sit, as well as at the other end of the engine near the crankshaft.)
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