Semroc Joe's Fin Jig II™   SEM-FJ-2 *

Semroc Joe's Fin Jig II™ SEM-FJ-2 *

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Semroc Joe's Fin Jig II™   SEM-FJ-2

Get your fins on straight every time!  

15 1/2" Aluminum Channel

Adjustable for fins as thick as 1/4"

Good for tubes as small as BT-5 and as large as 2.6"

Laser Cut Plywood Parts

Fully Assembled

Made in the USA


Instructions for use:


Loosen the both black knobs and pull open the jig to insert fins to align the fin width first. Once the fin with is even across the Jig tighten the black knobs. It is besst to use two of the rockets fins are a couple of scrap pieces of the actual fin to do this.


Premark the locations of your fins so you know where they go before loading the tube.


Load your tube in the cradle and use rubber bands to hold the tube down securely.


If the placement of the tube and fin cannot be made in a location that is appropriate there are some options to better your find placement location.
Use another identical tube and a coupler to temporarily extend the length of your rocket so the fin can be mounted on the rocket in a convenient location.
Or remove the screw under one side of the jig an move the leg into the L and re-secure. This will allow you to hang the rocket over one side to attach the fin in a more convenient location. This process creates a lot of wear and tear on the jig, replacement parts are available if you ware something out.


  • 5
    Definitely upped my game

    Posted by Velma Hopping on 21st Sep 2023

    Definitely upped my game when it came to straight fin alignment .

  • 5
    Highly recommend, speeds up the building process

    Posted by Velma Hopping on 14th Sep 2023

    just received the fin Jig, and love it already, perfect fin alignment, jig, is easy to use and will grow with me as we build bigger Rockets. Highly recommend, speeds up the building process.

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