The connection rods were a nice between-centers turning job, and then a selection of milling set ups.
Rather than write a lot, I will put some pictures below – the main thing to note was that almost all of the milling and boring was done with the partially machined big-ends attached to the partially complete rod – in order to ensure a good level of concentricity….
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- Facing the top of the big-end on the shaper, using “stop-pins” to hold it (and idea from a 1900 text book
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- …an even better view. Stop-pins hold the job down and central. and the shaper does not produce significant lifting forces. so all that is needed are the pins and a stop plate on the end of the table
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- Cutting flat face to lock big-end bolts
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- Cutting flat face to lock big-end bolts
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- Boring big and little ends at same setting to ensure concentricity. The DRO is used to find the mid-line of the castings – no marking out at all!
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- By bolting the rod/end to an angle plate ensures that the rod winds up square to the bores.
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- Using the DRO… first place cutter on the bed and zero display…
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- then raise cutter to provide exact width of little end bearing housing
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- Cutting the fork. Rotate thru 90-degrees, and use a vice to ensure that the rod in perpendicular – cut slot to width, and then use boring head to provide a clean foot to the slot.
SY Befur 
Subsequent analysis showed that the big ends and piston rod bearings were not entirely true. So while replacing the crank at the end of the 2018 season I re-machined these bearings as described here to get then true… https://sy-befur.co.uk/2019/02/19/steamboat-crankshafts-lessons-manufacture-pt2/