Fin/box Troubleshoot

To my great consternation: switched a fin into a new board and it won’t slide at back where the pin drops into the finbox; the rest of the base can sit fine in the finbox, but it just won’t slide back from the pin insertion point. Sanded it down a bit already, and didn’t see any glass drips in the box (though perhaps there’s some where I can’t see, like on the inside rim of the track where the plate slides). It seems site-specific, though I can’t tell if it’s an issue with the fin by the pin or something with the box.

Fwiw, fin fit fine into a different box; other fins I have on hand were slightly too fat for the box so I can’t isolate that variable. Any thoughts on how to fix this? I guess I could just keep sanding the base of the fin by the pin but I’m wary in case that’s not the issue, since it already works in other boards. Note: available tools are minimal (no power tools or chisels on hand).

Thank you in advance for pulling this thorn from my brain & helping me set the board up!

Does the plate slide freely, in the box, from one end to the other?      If it does, try inserting the nose of the fin(pin) and slide the fin into position, BEFORE you lower the base of the fin into the box.

Hi there-- great troubleshooting, thank you. I tried this just now and a) yes, the plate slides freely down the track but b) the pin does not. Thoughts? I haven’t encountered this before.

Inspect the PIN, to see that there are equal amounts extending on each side of the fin base.       If not, a few taps with a hammer will adjust the PIN’s position.       That should allow the fin to move in the box channel.

Thank you. Pin looked fine, but for an update on the end of this thrilling saga: I sprayed the finbox bottom/track lightly with wd40, wiggled the fin a bit so it worked its way back, and shaved just a tiny bit off the sides of the finbox with an exacto blade. I think the finbox was just a lil tighter than I’ve encountered. As in other arenas of life, some lube, patience, and gentle rhythmic pressure carried the day ; ) Thank you for patiently helping me solve this!

The FU/Bahne boxes are made in two pieces… the bottom plate portion is glued to the top and the seam is roughly where the interior plate slot is,  I’ve had some that were goobered up with glue in the slot.  I was able to bend the tip of a sharp tool and scrape it clean in the slot.  

Sometimes a box can warp a bit as the resin cures during installation.  A file or sandpaper can be helpful in bringing the main slot back in to spec if it has warped but using spacers in the slot can prevent it from happening in the first place.  Most boxes these days have bridges across the gap but I remove them and stick in a fin to check for vertical orientation.  The fin helps prevent warpage as well.