If the plastic shaft on your dart is broken, print and replace. Customize your name or logo into the shaft. The thread is not printed, as all you need to do is thread the printed shaft into the barrel and the thread will be cut into the plastic.I printed this using 0.1 layer height with a 20% infill. I did not use supports.Print lengthwise, do not stand. Laying down the print increases the strength and reduces the likelihood of breakage.