Repairing/Replacing a Bent Shaft

During the move of a recently purchased C&P OS 12x18, the shaft was bent at the flywheel, making the flywheel lean.

What is the best way to repair this bend or do I need to pull the shaft and replace it?


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Quick answer: replace the shaft.
However, before doing so, first determine the extent of damage by using a dial indicator to establish run-out. If not severe - say a sixteenth or so - try reversing the bend by applying pressure to the shaft at the point of largest deflection. CAUTION: DO NOT APPLY SIDEWAY PRESSURE TO THE FLYWHEEL nor JACK AGAINST THE MAIN FRAME; both will assuredly crack . Instead, jack directly underneath the flywheel relying on the weight of the press body to act as counterforce. Move in tiny increments allowing time between each attempt. You might just luck-in. The hurdle(s) you face in attempting to cold-straighten the shaft is the crystallization of the metal occassioned by the original bending, plus the short ‘lever’ stub which required great force to overcome. A machine shop should have facility to straighten the shaft but their hourly rates just might bend you out of shape.
So, again, replace the shaft. You’ll save headache - and expense. In my opinion.

Where can I get a new shaft?

If you can get a replacement original shaft that’s good, at least if it doesn’t cost too much. Or if having a straight shaft is not an issue as opposed to the orginal shaft with the center bend for a treadle you could use a new purchased shaft of the same diameter and length.

What I consider a better alternative is to have the original repaired. Keep in mind that only pressing the shaft straight will never prove satisfactory as it will not produce a completely straight shaft and the result will be excessive wear to the shaft bearing on that side. But a machine shop should be able to restore the original for you. They would do this by pressing it as straight as possible and then mounting it in a lathe and turning down about 3” of the bent end just enough to bring that end back into perfect allgnment with the rest of the shaft. They would then install a bushing in the flywheel hole to fit the slightly smaller end of the shaft. That should return everything to as good or better than new and use all of the original materials. Cost will depend on where you are located in the country and if you have any friends who are machinists. Around here it would probably cost about $150-200 or so.

If it were my press that’s what I would do. One reason is that a new shaft or antique original will not necessarily be less expensive and may in fact cost more. Also, the original shaft was fitted to the bearings and has run in those bearings for many years. At the point the shafts run in the bearings they were ground smooth to the correct size. So keeping the original shaft avoids any issues a new, unground shaft or a used one from a different machine might raise.

On the other hand, if a used original should turn up quickly for $50 I’d probably buy it. After checking the condition and fit at the bearings I would likely use it, especially since as the press operates at such a slow rate of speed none of the problems of tight tolerances that exist with high-speed shafts are present. But the chances of that happening are, at least in my experience, slim to none.

Hope this helps.

Rich P.
Front Room Press
Milford, NJ