If you have a small torch, try heating up the center stud until is smokes a little and see if that will free it up. Make sure not to heat anything non-metal and use a small pin-point flame/pencil torch (like below), not a big flame/tip like you screw into a larger tank.

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And when it is hot, try melting a little candle wax onto the center and let that wick down into the splines. Should be able to find a small puller at a hardware/auto parts store that may work as well.