How to Make a Crossbow Trigger Mechanism

Carve a latch from a piece of balsa wood. This holds the bowstring of the crossbow and needs an angle halfway down about 30 degrees from the perpendicular. The latch should have a diameter of about ¼ inch and be about 2 inches long, including the angle, although this depends on the size of the crossbow.

Carve a trigger using another piece of balsa wood. Two inches is a good length for the trigger, which should also be about ¼ inch in diameter. A straight trigger works fine but a curved end provides better stability for the user, enabling the trigger to be held half-cocked. Be careful when carving a curve that you don't carve the wood too thin; it should remain at least ¼ inch in diameter all over. Because the trigger and latch need to meet inside the crossbow, the length may vary depending on how deep the crossbow stock is. The stock is the main body of the crossbow and can vary in length and thickness.

Carve a small rectangular hole on the top of the stock where the bow reaches maximum tension. This hole should be as wide as the spring and approximately ¼ inch long to ensure compression of the spring. This spring will attach to the latch and rest in this hole.

Attach the other spring to the top of the trigger using Stix All, Epoxyset or Super Glue. The spring should face forward with the trigger curve toward the front of the crossbow.

Chisel a slot about 1 inch long in the crossbow stock forward from the end of the hole carved for the spring. This slot needs to be wide enough to accommodate the width of the latch.

Drill a small hole halfway down the trigger wide enough to accommodate the non-threaded bolt pin. Insert the trigger in the bottom of the chiseled slot and drill a hole in both sides of the stock to fasten the bolt pin through the stock and trigger. Make sure the trigger has approximately a half-inch free in the front and back of the slot to move. Secure the bolt pin and test the trigger. The spring should force the trigger back to rest once released.

Drill a similar hole in the middle of the latch where the angle is. Place the latch in the top of the chiseled slot and drill through the stock to match the latch hole. Glue the top spring to the top of the latch, pointing backward so it rests in the slot carved earlier. Glue it in place in the slot. Fasten the latch in place using the bolt pin. You may need to pull the trigger before the latch will fit.

Test the mechanism by pulling the bow string over the latch. The end of the trigger inside the stock should hold the latch and bow string in place. Pull the trigger to release.