Machining a miniature 4-cylinder Crankshaft.

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As in my previous guide on machining a V12 crankshaft, I present the steps to build a 4-cylinder crankshaft fit for in-line four-cylinder engine.
The method presented corresponds to my machine tool set and can therefore differ from one person to another. This method is not the only one, but it is possible to have inspiration for this rather complex type of realization.
This also according to my conventional machine tools units. So, no CNC or serial production.
It is perhaps futile as a remark, but many times observed on the reality: before starting job, you must be relaxed, clear minded and free of any stress. Do not have physical training or have drunk exciting or energizing drinks.
Study the plans well and remember the machining scenario, or better say: the machining sequence.
The more you progress in the works and the more the depth of cut have to decrease.
In other words, at the beginning 1mm milling cut are not shocking. But towards the end, a tenth of millimeter may seem excessive.
"Work” on one dimension at a time. Focusing on multiple ratings at once will inevitably lead to mistakes. And the more you progress, the more critical are the errors.
(Ph 1 1 & 2) For this crankshaft, I started from a block of 42CrMo4 of 300x60x20mm and 2850gr gross weight. Chrome-Molybdenum Allied Steel.
The first thing to do is the final length setting, which is 292mm.
LeZap

 

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(Ph 1 3) Then draw the six centers of the three virtual axes of the crankshaft, the master and the two axes of the connecting rod.
Personally, I used my DRO for maximum accuracy, but a carefully tracing with a gauge is just as good. Note that, at this level any error of one tenth of a millimeter is perfectly tolerable. Indeed, in the worst case, a cylinder or two will have two tenths more stroke. As for the squaring of the connecting rod, the error brought back into an angular offset will be perfectly negligible.