Making A Crankshaft – 5
Another half day workshop session.
I decided, after advice from several readers, to rough turn the mainshaft.
But first, just in case you were wondering, the kitchen entry stairs are finished, except for a bit of painting.
But just in case kitchen stairs are not your thing, back to the Fowler R3 traction engine crankshaft ….
Today I rough turned the mainshaft.
First I tested and adjusted the tailstock offset.
Then mounted the crankshaft blank between pre-drilled centres…
And turning towards the headstock. This was interrupted turning +++. I took 1mm off the diameter, then as I became adjusted to the machine gun rat-a – tat-tat, gradually increased the depth of cut to 1mm, with a spindle RPM of 175/min. Later I added coolant. Note, I used a ball bearing tailstock centre for the rough turning. I will use a solid centre for the finish diameters.
I was not too fussed about actual dimensions. They were roughing cuts, and at 38mm diameter there is plenty of extra material. It should be much smoother machining to reduce the diameters of the cylinders, compared to rounding the square sections.
After getting quite a few opinions about stress relieving the workpiece, after all of this machining, I have decided to take the workpiece up to 600deg c, for 1.5 hours, then slowly cool. Probably unnecessary, since it is black steel, but it can’t hurt. Then I will do the final dimension turning.
p.s. about a week later. No detectable movement despite a lot more material removed. And some further expert advice that heat treatment might actually cause problems. So, given the controversy I have decided to do nothing. ie. No heat treatment.
Great work John!!
Getting there Neil. No major stuffups. Yet.
Yes it was good to see the progress.at the club …. I don’t know how you find the time!!