How To Repair The Fiber Optic Thread on Your Bow Sight

I recently upgraded the sight on my compound bow to a 4-pin Sword Apex Hunter. I had purchased the bow used off the forums and it came with an entry level Cobra 3-pin sight. It took me about a year to realize the sight wasn’t up to snuff, and decided to upgrade. If you’re still toying with the idea, go upgrade your crappy sight. It’s the nerve center of your bow, you can’t shoot when you can’t aim!

The sight, while being absolutely diesel in it’s construction, came with a pin that was a little too bright. After contacting Brandon over at Sword (great guy), they told me that the fiber optic thread was not clipped close enough to the pin hole. They recommended that I clip the end of the thread and use a lighter to very carefully flare the end so it would not pull back through the hole.

I, unfortunately, held it too close and “killed” the pin. Which means I burned the fiber optic which causes the end of the fiber optic to emit as much light. I therefore took it apart and pulled more line through and fixed the pin. In the process, I accidentally broke two threads while trying to pull more slack from the wrapped threads. After fixing one correctly, I figured I’d document and explain how to do it while I fixed the other one.

Below, you can see how the top pin (in green) emits almost zero light, since the thread was broken. The only light it is pulling from is the 2 inches of thread left after the break, rather than 12” of thread in the wrap.

1. Assemble the tools needed for the job. I used:

  •  carpenter’s nail
  • hex head (allen) wrench set
  • pliers
  • needle nose pliers, hemostats, equivalent
  • nail cutter or line nipper
  • bodkin, or thin needle
  • heat source (lighter or blue-flame utility torch)

2. Remove any extra’s on your bow, such as a detachable quiver, stabilizer, etc. Anything that can get in the way of you positioning your bow and working on it.

3. Now, and depending on the sight, remove the sight window, which protects the pin and houses the bubble. Yours may be removed differently, so inspect your sight and determine how to do it. Here, there are just two 9/64” hex-head screws that lock the round sight window into the frame.

Here, you can get a better picture of where the break in the line is. This was caused by trying to pull the thread through without unwrapping the tubing and freeing the fiber optic. The tension snapped the line as it runs through a hole in the base of the pin.

4. The protective clear plastic tubing that sheathes the threads is held in place by two set screws, a 1/8 and 1/16th” hex head. Remove those.

Word of warning: Remove small set screws like this on a padded surface, or at least on a table. If you drop it, you’re going to spend a long time searching for it as these screws tend to run when they hit the ground. Sure enough, while trying to photograph removing the set screws for this post, I dropped one. I spent 10 minutes trying to find it in the carpet. I did learn a good trick for finding it, use a high output flash light! Hold it low and look for the shine of the screw.

Can’t see it from here..
Getting closer..
Good luck trying to find that!
You can definitely see the shine and shadow now.







5. Anyways, let’s continue on. Carefully remove the tubing from the origin, not the from where the threads exit to run to the pins.

6. Remove the old or broken thread. Using needle pliers or tweezers, pull the thread from the pin head hole. If a piece of thread gets stuck inside the hole, use a needle or a bodkin if you’re a fly tyer!

7. In the case of this Sword sight, tiny black rubber bands are found on each pin to keep the thread fixed on the pin. Remove this prior to running the line.

8. Using pliers, tweezers, or hemostats, very gently pull more fiber optic thread from the wrapped gang of threads. Make sure it’s the right one!

9. Pull enough line through to enter through the pin hole a few millimeters. Replace the rubber band and gently roll it up the pin toward the base. Don’t worry if the line rolls as you push it, you can turn the band to realign the thread.

If you have extra slack in the line, pull more thread out the front of the pin hole to remove the slack. You want the thread running as flat as possible up the back of the pin, if there’s too much slack, the thread can bow out and sometimes be visible while looking through the sight in use.

10. Now, for the fun and dangerous part. Keep your finger on the back of the pin and clip the thread as close as you can to the pin while leaving a hint of thread visible.

11. Take a standard carpenters nail in a pair of pliers and heat the nail head with a lighter or utility torch.

12. Take the heated nail and hold the head close to the nipped thread. The heat from the nail should be sufficient to flare the thread enough to hold it in place without burning it.

13. Check the fiber optic by looking down the sight. If satisfied, rewrap the the protective sheathing, and reassemble the sight.

Done! Not so bad right? Hopefully it wasn’t as hard for you as it was for me and you don’t make the same mistakes I did.

Good luck and tight groups!

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  • I recently started getting peoples old sight when they would upgrade & repairing them to resale or in some cases, give em to a kid entering the archery world which in this day & time is a tradition that is ever falling to video games. I could not figure out how to melt the ends of the fibre optics back & I thought surely somebody else has had this problem. If I`m the only person this article has helped, I send you the Thank You`s of a 1000.

    • You’re very welcome. It’s a far easier trick to just use a nail then risk burning the end with an open flame. And good on ya for passing them down to newbie archers!

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