the 3 notches are for a "c" spanner to turn the mushy to where you want it .....a bit like the spanner from years gone by to dismantle a bicycles crankshaft you dont really need em....and you dont need the very shallow taper just make as a turret the critical dims are the taper which is 3 degrees and the outer dia for the sierra hub carrier which is 45.5mm get them two right and you will be ok
I have made several styles before just check some of my other posts
this is how I make them now
