Starter Spin
                                                                                                             

I don't know how many times I gotta tell you guys - use some Loctite RC609 Retaining Compound on that shaft.  Red loctite is threadlocker, and isn't designed for shaft shear coupling like 609 is.  The high-temp version is RC620.  You won't even need to lap the fit together - it's advertised to fill .010 gaps. Get some Loctite primer to put on one surface, RC609 or 620 for the other, then secure the bolt with either red or blue Threadlocker.  We use the stuff at work, and it takes the place of Woodruff keys.
                                                                                                                             

(Patrick Sills)