This guillotine-style fin alignment jig is similar to the design from Macklin Missile Works. It provides convenient and accurate attachment of fins to model rocket body tubes. Three sizes are available (mini, small, and large) to accommodate a wide range of tube diameters and lengths. *** For personal use only ***

Suggestions for improvement are welcome!

MINI:
The mini jig works great for your typical hobby rockets, especially the short ones. It can handle body tube diameters up to 1-3/4 inches (45mm). The base is about 4" long. It was perfect for my Estes Bullpup 12D. You will need to print two copies of the mini clamp if you have a large enough print bed (300mm x 300mm), otherwise you will need to make your own clamps as described below.

SMALL:
The small jig is a good choice for the majority of hobby rockets. It can handle body tube diameters up to 2-1/4 inches (58mm). The base is about 6" long which means it cannot be used with body tubes shorter than your fin length + 6 inches. The large jig is too long for many body tubes.

The clamps require a large printer bed (300mm x 300mm). If your printer is smaller you will need to make your own clamps as described below. The MINI clamp will work on both the mini and small jigs. The SMALL clamps was an early version and only works on the small jig.

LARGE:
The large jig is suitable for long rockets with tube diameters from 3/4 (19mm) up to 3-1/8 inches (79mm). The base is about 9" long which means it cannot be used with body tubes shorter than your fin length + 9 inches. It also requires a LOT of filament and takes a LONG TIME to print (2-1/2 days). Make sure you have enough filament before starting!

You will need to make your own clamps for the large jig as described below.

Additional hardware is required for each jig! The Amazon links to the items I used are for reference only. I am NOT affiliated with Amazon or any of these products.

• (8 per jig) M5x25 screws - for both small and large
• (8 per jig) M5 Female Knobs - for both small and large -- Knob diameter must be 25mm or less!
• (2) Clamps - 1.5 x 1.5 x 1/8 by 16 inch angle aluminum - better suited for the large jig (1/16 inch thick is probably sufficient but I haven't tried it).
• (2) Clamps - 1 x 1 x 1/16 by 12 inches long angle aluminum works well for the small jig

1. Check the fitting of the End Panels between the guides on each end of the Base. If needed, gently sand or file the sides of the End Panel until the panel slides between the guides with little resistance.
2. Use an M5 screw to create threads in the 6 holes for each jig. KEEP THE SCREWS STRAIGHT AS YOU SCREW THEM IN (not at an angle). The holes are not threaded and will require moderate force to form the threads.
3. Now fully thread an M5 screw into each hole until the head is just SNUG against the surface. The screws in the Base start from the inside of the box. The End Panel screws start from the underside of the v-notched flange.
4. Attach End Panels to base and secure with knobs.
5. Make a pair of Clamps for your jig. NOTE: They need to be "mirror images" of each other (NOT DUPLICATES). Cut 1/4" (6mm) slots to match the distance between the knobs on each end of the box. Spacing is approximately 6-9/16" (166mm) for the small jig and 9-3/16" (233mm) for the large jig.
6. Install your Clamps and secure with knobs.