So the engine side of the clutch disc would still have spline engagement. The rear would not, but relieving the corner would prevent it from binding….
Is that basically the theory here?
The clutch hub splines are roughly 1” front to back. Trimming (chamfering) the rear inside corners by 1/8” still leaves plenty of hub spline for strength. Notice how the input shaft grooves begin to taper as you go towards the gear end. Another way of saying that is the diameter of the shaft starts to taper back to normal as the groove becomes more shallow. It’s the tapered shallow area that prevents the clutch disc from moving any further. So lengthening the splines gets rid of the tapered shallow area and that works fine but chamfering the clutch hub also works and a clutch disc is easier to work on.
