Our customer operates a relatively large, high cycle rate press that consistently “wallowed” out the key way. As often happens, this situation snowballed until the key failed and the shaft was damaged.
Despite careful attention and tighter tolerances, they still found that this was their most frequent maintenance problem with the press.
The keyway involved was located in the hub of the air activated clutch on this press. Despite some significant space constraints, we were able to come up with a hub modification that included a mechanical clamping device.
This approach eliminated all of the clearance. As a result, they no longer experience key failure. You may want to try this, if you are limited by key life.