So I learnt never to loosen my fin screw before I'm actually removing the fin today! I loosened it while drying my gear... Then forgot and flipped my board over to carry it. Needless to say I've lost the fin screw and the rubber washer somewhere on the sand at St Kilda beach.
Am I better of replacing this at a windsurf shop, or will a normal screw from a hardware store suffice? What are the measurements for modern fin screws? Or do they vary from brand to brand? Also I assume it needs to be made of something that doesn't just rust in saltwater.
Feeling a bit stupid 
Great, thanks, so I need an M6 screw :) Not sure what the length of the original one was. My board is a JP Explorer 145, so I'm guessing it would probably have been 35mm, like other JP boards. I might have to buy a few in different sizes and see what fits. Suspect I'll end up hunting around where I work and find nothing, so finish up driving to Sandringham just for a tiny little screw anyway! I went to The Zu in St Kilda right after I lost it and they had nothing. The guy didn't even seem to have the slightest clue, as he was picking up little 10mm screws from a plastic container and I was like "Umm, that's not really going to fit".
I just cut mine to length with angle grinder and file end at 45 degree angle, put a nut on it then into the fin. Too hard to find the right length screw all the time. Have a look at starboard's website as well you will find some interesting info on fin bolts.
when u find em - get spares 
i have left the one i needed in the fin that is at home
the spares saved me on that day !!!
A great trick is to add an oversized piece of plastic (old sail material works well) washer. Ie this washer is flexible and too big to fit in the outer hole. Then when you remove the fins, you can leave the bolts in the fin slot and this washer holds them in.
So after much hunting around, Sundance Chandlery at Sandringham have them, although they'll probably have to cut one down. I'll drop in on Saturday morning to figure out the right length. I have also ordered a whole bunch from a couple of online stores last night, but they will also need cutting and they're not likely to arrive before Saturday, which means I'd miss a weekend on the water!
Go to a proper fixings place that only sell bolts and screws. You will have a choice of M6 stainless from 15mm to about 150mm, in 4 different heads.
They will cost 50c each - instead of a marine place who will charge like a wounded bull and a fee for cutting it no doubt.
50 cents each? The stainless place around here charges about $2 each.
Just remember that if you have the space you can add nuts to the screw to reduce the effective length. You can even get away with steel screws if you don't leave them there for long. They corrode very fast.
In a pinch I've used two nuts locked against each other to 'shorten' a screw. I've also worked out a way to get the exact length of screw required by putting a nut on the screw and screwing it into the board/fin. The nut starts to spin when it hits the board. You then unscrew the screw, and the distance to where the nut is the exact length you need.
Select to expand quoteDean 424 said..
M6 stainless and I use just take the rubber washers off the tap washers
Have to second that (TAP WASHERS) one of the best fin bolt tips I could give anyone.
d11,
SHQ have the bolts.
If you need to go to a bolt bar, take the fin you are trying to mate with you, as bolts/screws/cap screws come in length, thread diameter and thread pitch. From memory, JP's use an M6 x 1.5 pitch (Metric, 6mm diameter, thread pitch of 1.5 mm [the distance between the "hills" on the thread]).
To try to stop losing more bolts, as soon as you take the fin out of the board, remove the bolt and screw it back into the fin.
Hope this helps.
Oh, do they? I actually tried emailing them twice and got no reply. I guessed they'd likely have them though, as that's where I bought the board and the fin from, which (obviously) came with the bolt. I was going to Sundance Chandlery in the morning anyway, which is on Jetty Rd, so I'll drop into SHQ first and see if they have the right bolt on the spot. I think Sundance were going to have to either cut one down, or make one longer.
Definitely won't be unscrewing the bolt before I'm actually taking the fin off in future. You learn from your mistakes, right? :)
I thought M6 meant M6, and implied a thread-pitch of whatever an M6 uses. I am guessing its 1mm for a m6 just from that ebay ad, but I am surprised if it varies. I don't really know, but this has always been my assumption.
The board is really going to dictate the length of the bolt/screw, so unless you take the board with you, you are shooting blind. If you really want to work it out, try my method of using a nut on a screw, and a tape measure.
This is a basic way of measuring thread pitch below. If you don't want to strip a screw or bolt, you need to do this.
From what I can make out on my JP and Naish fins (((Powerbox))), the pitch appears to be 1mm. Best way maybe to go into a bolt/ screw retailer and physically screw in the screw that fits properly.
Hey I googled it, and am now an instant expert. Just ask me! 
It seems that for M6 and other metric sizes there can be a coarse pitch and a fine pitch. If the pitch is omitted in the description, it is assumed to be the coarse size. For an M6 the coarse size is 1mm and the fine size is 0.75 mm.
I have never ever seen a fin screw with a fine pitch, and the only other fin screw type I have seen is an imperial 1/4".
I'm sure if I'm wrong, someone can help me out.
What the heck, I will add the following. The Euro fins and anyone sane uses M6 (1mm pitch), and the US sourced fins seem to sometimes use a 1/4" screw. I have never heard of a different screw.
Select to expand quotewindlure said..
When you talk about IMPERIAL do mean him:
Well you saw what happened to the death star. It was definitely screwed.
Select to expand quoteFormulaNova said..windlure said..
When you talk about IMPERIAL do mean him:
Well you saw what happened to the death star. It was definitely screwed.
Now that's a thread
SHQ just gave me one, free. Those guys are really helpful every time I go in. I found The Zu in St Kilda to have a bit of an attitude.
Chaps,
I wuz wrong. Wrote the thread pitch answer at work, so did not have bolt to check.
FormulaNova is correct, the pitch is 1.0mm, so the bolt spec is M6 x1 x bolt length. Of course you WERE going to use a Stainless Steel bolt, weren???t you?
Also, Formula, I didn???t know that if the pitch was not in the bolt spec, it is assumed to be a coarse pitch. Handy info, that.
In passing, Bunnings and Repco have bolt stands in their stores and the stands incorporate nuts of various diameters and pitches and bolts of various diameters and pitches. You can screw in your sample to make sure you are buying its correct mate. This would overcome trying to work out Windlure???s thread pitch on his bolt closest to the ruler.
Very handy thread, this..
