The Speardiver Shaft Drilling Jig guides a 3/32" drill bit, which is the standard diameter for a flopper pin, to make perfectly centered holes in shafts ranging from 5/16" (8mm) in diameter and down. The 3/32" hole can then be used as a pilot hole if a larger diameter hole is needed. The jig is 3" long X 1" wide X 1" tall.
- Quickly and easily change the length of a shaft and reposition the flopper
- Add a pin for loading another band
- Increase band stretch by putting a pin closer to the trigger mechanism
- Add a rest pin for ease of loading
- Add a pin to keep one band at minimal stretch when powering down, rather than leaving it to flop around
- Add a pin to rig a Heinrich line release
- Make stringers from old bent shafts
How to use the jig
Slide the shaft in the jig, choose one of the 5 holes and position it over where you want the hole to be. Tighten the two Allen screws, the shaft is then held securely and the jig automatically centers and guides the drill bit. With a drill press hand pressure is enough to hold the jig and shaft. If a hand drill is used the jig can be secured in a vice. After drilling the hole turn the jig upside down, there are 9/32" holes on the bottom of the jig corresponding to the 3/32" holes on the top, use a 9/32" drill bit in a hand drill to deburr the bottom of the new hole and allow removal of the shaft from the jig. Blow out all debris so as not to jam the jig, loosen the Allen screws and slide the shaft out of the jig.
The jig is available Spearfishing Store Speardiver Spear Shaft Drilling Jig
What a pleasure it is to use the Speardiver jig after 10 years of making these holes with an electric hand drill, sometimes without a vice to hold the shaft. The drill bit would dance on the round shaft surface even when I'd use a file or a punch to mark the metal to start it off. The resulting holes were rarely centered, and would rarely run straight through the shaft on any plane. The process would take up to 20 minutes and was exhausting. I'd have to stop at least a couple of times to sharpen the drill bit and a few more times just to rest. Sometimes because of putting sideways pressure on the hand drill the bit would break right when the hole was almost finished. If the drill bit broke off close enough to the shaft, the shaft would be scrap as there was no way to get the drill bit piece out, and repositioning the flopper was no longer an option. Holes that were not straight interfered with the proper deployment of the flopper. I recently bought a drill press from Harbor freight for $70. With this drill press and the jig it takes me less than one minute to make a perfect hole in a stainless steel shaft with a cobalt drill bit.
In Cuba for lack of tools and materials I've seen them use one of these hand drills. Now that was pure torture and would take hours for one hole 
