Select to expand quoteBen1973 said..Imax1 said..Ben1973 said..Imax1 said..
On all my fins I drill a 5 mm hole about 5 mm deeper than the nut . Then tap the hole . That way I can use a slightly longer screw that goes all the way through the nut . All my fins are powerbox and only have one nut so I want it as solid as I can get .
In case anyone wants to know , on fin bolts , one turn of the screwdriver is 1 mm in bolt length . It's a way of calculating how far your threading into the nut . Minus the lead in chamfer which would be about 2 mm.
Thats enough from me .
Why not drill a bigger hole then you wouldn't have to tap it
youve been lucky if the threads you've put in the fin line up with those in the bolt
But more important why do you only have one nut!
You leave the nut in while doing this , then the thread lines up and you don't have to knock the nut out . If I was replacing the nut i would drill a 6.5 mm hole .
That works, I read as you only had one nut and were using the same one in all your fins.
I see the confusion . You read right , I righted rong 
There's quite a difference in screw length between some of my fins. Now I tend to leave the screws in rather than risk swapping them around.
