Making the Crankshafts

With the shafts for the cranks ready, it is now time for the webs and crank pins.

The webs were machined to 25mm from 1” stock. The shaft hole was drilled to 5.5mm and then reamed out to 6mm to fit the shafts closely. They will be attached with Loctite 603 (or more likely the affordable alternative from Weicon). Cutting off went quite well, having a strong lathe makes this so much less traumatic. The webs gave me some challenges as they are only 6mm thick after cutting them off the raw stock. Holding these straight in the 3 jaw was not easy but I ended up using a piece of 6mm rod in the tailstock chuck to align the web. This let me face the second side and reach the 6mm target dimension.

Crank webs installed

 

I  used the milling machine to drill the hole for the crank pin. This is offset 7mm from the centre of the main shaft. I left this slightly undersized, 4.9mm drill for a 5mm pin. This allows for a firm press fit, thus avoiding silver solder on that joint as well. I test fitted one of the bearings, a firm fit.

7mm offset for the crank pin20170130_175111

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My main learning from these parts is that the cutoff blade has to  be a) sharp, so use a stone to polish it after grinding, b) make sure it is exactly perpendicular to the piece being cut to prevent convex cuts. The result is clean cutting even on 1” diameter material, including stainless steel.

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