Hopefully a easy question and one that doesn't sound too stupid... I am replacing the ' cooling fan' on the OS MAX 50 and after taking it off, the fan, and the back plate collar..I notice there is a 'key way' but no key in there, and I didn't drop it, didn't loose it...so does it need to be there or does it matter? Wouldn't be difficult to make and I know how, if it needs one, should it be made of steel or aluminum? thanks again for everyone's help, I need as much as I can get, it seems, as I get older. Blessings to one and to all, As Always, I Remain...