MLA Crankshaft and Bearings

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I got some rough finish 932 Bronze bearing material and turned it to an interference fit of 0.001" (or so).  It comes at 1.300" and I needed to turn to 1.200"  I snuck up on the last .010" very gradually, the bronze is expensive.


Light taps with the Compothane hammer got it this far.


Turnin' Bronze

Whaling on it set it the rest of the way!


Inside view, it projects about 0.250".  Next step is to mount the casting back on the mill and drill, then ream the shaft hole.


Crankshaft assembly

I neglected to take any "action shots" during construction, sorry. 

I machined a 0.625" diameter end on the shaft 0.500" long.  The shaft is O1 drill rod.

I then made the disk from CRS and machined it 0.500" thick and reamed it to an interference fit with the end of the shaft.  I doped it with JB Weld slow as a precaution, but having to use the big hydraulic press tells me that was just for peace of mind.

I then drilled and reamed a hole 0.500" from the centerline for another press fit of the 0.250" hardened pin.

I will decide later how I am going to handle the pulley end of the shaft as far as a Keyway or a flat. 


Due to the very light load and slow speed I took the easy way out and just cut a flat on the shaft.  This will work fine for my purposes and I would have to order in a woodruff key slot cutter otherwise.


Playing with the machine after the test assembly I decided to shim the shaft a little to quiet it up.  I found if I placed my finger on the end of the shaft, the noise of the machine was reduced to nearly zero.  I picked up a couple of 18 gauge steel shim washers.  These measured out at 0.050" and were way too thick, so I put one on the surface grinder and cut it down a bit, testing the fit as I went. 

Shaft shims

At about 0.025" the end play in the shaft was slight and the machine ran quietly.  Sealed back up and filled with oil the motor is louder than the filer mechanism and the whole thing sounds like a nice sewing machine as it is running.



First drilling

I decided, since bronze and I don't get along together very well, to drill the part out in several steps to just under the 0.751" target.  The power down feed made the drilling go smoothly.  I then took it the rest of the way with the boring head.  5/16, 3/8, 1/2 5/8 inch bits were used.


Second Drilling

and then 23/32".


Boring head

Boring head to take it out to 0.752"  The fit is excellent!

Finished crankshaft bearing

Here's an inside shot of the housing with the crank shaft bearing visible.  The fit when installed was awesome, I haven't measured it but I swag it at 0.001 to 0.0015

Next step is to roll the casting over and counter bore the housing for the back plate and drill and tap the retaining bolt holes.


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