CRANKSHAFT – early steps
by John
The triple expansion steam engine crankshaft has 6 main bearings, 3 big ends, and 4 positions where eccentrics attach.
It is about 240mm long, machined from 50.8mm mild steel rod.
The mains are turned from centrally positioned centres, the big ends from eccentrically positioned “centres”.
The centres were drilled on the CNC milling machine, after the locating the top of the bar
The eccentric centres were calculated, and drilled using CNC to get the positions. The longitudinal scribed line was used to position the other end of the rod.
Turning between centres, using a lathe dog. This will not be a quick job.
And this is how I would like to make a crankshaft…
johnsmachines 
Why is the toolholder on the right hand side of the toolpost rather than on the left?
john f
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That is the only way I could fit it in the short space. It looks odd but worked fine. John
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