In Reply to: Re: flywheel gear posted by Ultradog MN on January 16, 2020 at 18:36:48:
I cut my NC Turret Lathe Machining teeth on Ford 6375 flywheels beginning in 1975. I’d turn both sides; one Warner & Swasey 2SC on clutch face side, another side by side in a cell for engine face. Then they’d go to the NATCO drilling machining for all the holes and then to a gang drill for tapping and reaming. From there went to the parts washer then to ringgear assembly. We had a gas oven to heat a stack then a worker set each one on a flywheel and pallet. Once cooled, they went back to my lathe to get the clutch surface re-faced. The cast iron flywheel ringgear diameter tolerance is ± .002” and the ringgear is tempered steel, spec’d at .060” smaller than the flywheel diameter. There is an undercut in the corner of OD and seat so gear sets flat. OEM ringgears had a chamfer on one side if one ID and had to be assembled with that chamfer facing down into the flywheel OD seat so it seated down flat. Heating expands the gear to slip onto the wheel, as interference fit process. Reface is done after so any warpage makes sure the crank bore is all square to the world with clutch face w/n .005”. Assembled flywheels then get balanced on a special machine and packed in FORD logo marked boxes then shipped to service centers all over. Ringgear slippage was mostly due to when aftermarket suppliers started making the ringgears without that ID chamfer and they would ride up. When the gear slips, the flywheel OD will get glazed and thus usually won’t hold a gear anymore. Like Ultradog said, flywheels are cast iron and if the steel gear is tacked on with the wrong welding rod, probably won’t hold. Continuous slippage only gals up the flywheel further. I learned a lot about flywheels and ringgears. I still have the OEM drawings as well as most all of the 9N tractor drawings. I spent 20 years at that company working my way up to engineering as I got my degree at night school during that time. When I left in 1995, they went out of business a year later. From there I worked at Valenite Modco Tools til 2002 when they were sold.