I just received a new weed fin. Checking to see if it fits the board I find that I can't tighten the screw.
Closer inspection shows me that the barrel nut is just slightly off alignment, but I can't budge it with a normal screwdriver.
Anybody got a tip for how I can loosen it enough to twist just a little to get it right?

If that doesn't do it, (and it should), heat and cold may help. I think I'd try the freezer first, I have an inkling that the expansion rate of brass is greater than fibreglass, so cooling it may just loosen the nut. Certainly brass will conduct quicker, so timing could be important. If you remove from the freezer once the brass has contracted, but before the fibreglass has, that should help.

The other possibility is that heating and expanding the nut could compress the fibreglass enough so that once it cools it will be loose.

Good luck anyway.
If you succeed get back here with the method

All fin bolts should be M6.
Try the bolt In another fin . If it fits it's the right thread .
You probably need to run a M6 tap through the fin nut . It's possibly not tapped through all the way . Make sure the bolt is not too long .

Not quite all fin bolts/inserts are M6. If the fin happened to have come from the USA, there is some chance that it is 1/4-20.

Yes, first figure all this out without inserting the fin into the board.

OK, I have it almost fixed.
Freezing it didn't seem to have an effect. Banging it with a hammer has centred it in the fin.
Sadly, I managed to damage the thread (or the thread was already bad) when I was initially trying to force the bolt in.
So I bought another M6 bolt with a hex head and used that with a spanner to cut the thread again.
There is still a slight verticality problem with the screw so that the fin is not sitting perfectly flush in the board, but I think I'll find a way to rotate the barrel nut a degree or so to correct that

kato said..

Mr Milk said..
OK, I have it almost fixed.
Freezing it didn't seem to have an effect. Banging it with a hammer has centred it in the fin.
Sadly, I managed to damage the thread (or the thread was already bad) when I was initially trying to force the bolt in.
So I bought another M6 bolt with a hex head and used that with a spanner to cut the thread again.
There is still a slight verticality problem with the screw so that the fin is not sitting perfectly flush in the board, but I think I'll find a way to rotate the barrel nut a degree or so to correct that

If the thread is damaged, I'd drill out barrel bolt and fit a new one. Not worth re tapping brass

Knock out barrel nut with a punch .