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"On The Tractor" Crankshaft Spline Repair
Before you replace a worn down crankshaft, consider reconditioning the splines. Glen Delisle did just that on a John Deere Model A two-cylinder tractor. Best of all, he did it without removing the crankshaft from the tractor.
"I needed to recondition a shaft to fit the clutch hub," recalls Delisle. "I used a welder to build it up and then used a compound machinist vice to grind it down."
Drive splines inside the clutch hub were squared and trued with what Delisle calls an "overgrown" hacksaw. That was done by hand.
Delisle says the complicating factor is having to address rotational and centering tolerances on the shaft splines. He bolted a special bracket to the engine block alongside the shaft.
The bracket was a piece of channel iron with a floating steel plate that could be raised, lowered and moved in and out on threaded rod. He then mounted the machinist vice to the plate to hold a high speed, air powered die grinder. The rods allowed him to get the exact height and placement he needed.
"The compound machinist vice has a double set of V's like a tool post on a lathe, so you can feed the die grinder in and out," says Delisle. "I adjusted it so it was dead center over the crankshaft. This allowed me to slide the die grinder parallel to the shaft and grind it to the required tolerances."
The tapered centering splines required a light cut taken off of each as the shaft was rotated.
Although it took him two attempts at rebuilding and grinding, Delisle says he succeeded. As he worked, he tested the out-of-true wobble of the the clutch face many times. When he reassembled the clutch hub and shaft for the final time, it rotated with a wobble of less than 1/5000 of an inch.
"The clutch works very smooth now," he says. "I was stuck at first, but this method works."
Contact: FARM SHOW Followup, Glen Delisle, P.O. Box 464, Spiritwood, Sask., Canada S0J 2M0 (ph 306 883-2144).

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2011 - Volume #35, Issue #4