whats the best way to lighten up a loose key way from the shaft to the U joint.

Tack weld it to the u joint

hammer and punch the shaft to pinch the key way

or machine a set screw o the u joint

what you all think?

Talkin about the yoke? The Yokes I bought for mine came with a set screw hole and a keyway. Got the shaft keyed and replaced the set screw with a bolt with a hex head. Guy I know said that you just cant generate enough torque with an allen wrench to tighten it down very well, and its the truth. Get your yoke where you want it and use some red loctite on that bolt, crank her down tight. If you really want, you can tighten it down without the loctite once, pull out the shaft and where the set screw/bolt made contact with the shaft drill a SMALL DIMPLE in the shaft NOT A HOLE. This just helps give the set screw more bite. I pinged the key and it stayed for a while but broke loose from the vibration, however it doesnt have enough play that it can escape the yoke or shaft keyway. I would think tack welding it would work pretty well but you just gotta remember you gotta make it fit in that yoke! - Maybe someone else will chime in on this. Long winded but hope it helps!

Use an oversize key, get a square head set screw not just a regular bolt. set screw tips are made to bite. then use green loctite for slip fit or tack weld it. if you tack it remember, your gonna have to take it off some time or another.

Could you just drill all the way thru yoke and shaft and run a bolt thru both?

i think the key way is there to break. if you made the key super strong then its gonna be a yoke universal, drivshaft, or crank if you hit a solid object. somethings gotta give. id rather it shear a $2 key than anything else.

Drill enough of a hole to seat they keyway. I will stay seated and you will be able to remove when needed.