Lube the splines...

Sorry, I don't recall the size on those, but they were common metric size nuts available at the hardware store
I had issues with them, I bought proper stud remover and installer, those nuts and bolts slipped on me, I remember running to other city to get new one, I even ordered blacked/so called hardened ones from overseas but that also slipped,

just be careful where you getting those from.
 
or get a proper stud remover with 1/2inch drive