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Broken hex wrench piece drill jig
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Broken hex wrench piece drill jig
I just opened a repair shop and the first repair was to remove a broken 1/8″ hex wrench ball end from the truss rod nut of a Turner RB4 Renaissance Bass. I read of all sorts of theories on how to extract/remove. None of them had recorded actual attempts of the theories. There’s probably others on here but I haven’t found them.
The ball end was loose and mangled at the rear of the nut sleeve. I tried fairly benign methods first. Heating, magnet, shrinking, mini pry bars etc., all to no avail. I finally decided on drill/extractor. The main worry was not to damage inside of hex walls of nut as I didn’t want to render it unusable. So the idea was to somehow create a more precise way of holding drill bits so they wouldn’t wander around and drill a hole centered on the broken ball end. I consulted with my genius machinist friend and he suggested that I use a drill point countersink bit. Then the other end of the idea hit. Idea being to use the nut as a bushing on one end and to fab a bushing for the other end of the bit. I made a drill bit jig out of sheet metal (see pic). I then needed to find drill bits for the operation.
I had requirements and wasn’t sure if I could find a drill point countersink that would work. I needed the shaft to be 1/8″ as the nut hex opening was slightly larger to allow for a wrench and this would allow just enough clearance to use as a bushing for that end of the drill bit. I found the perfect size on McMaster Carr. The bits used needed to be at least 6″ long to clear the head stock and allow for drill chuck clearance. I filed the material extractor flutes on the drill point bit dull in case they hit the sides of the nut. Next, I tapped the broken ball end firmly to the back of the nut to fix it in position for drilling. Next, I aligned the sheetmetal jig with the bit in place by spinning the bit as I moved the jig up and down and side to side so that the bit spun freely without the flutes digging into the sides of the nut. I used a couple of clamps to hold the jig in position. Next, I hooked up an old Makita 9 volt variable speed drill to the bit. I opted for this because of it’s small chuck and variable speed (it fits into sound holes quite well too). Then I marked the bit on the nut side of the jig to use as a depth guide (I measured the width of another ball end for reference). I put a drop of oil on the end of the bit and inserted it until it touched the end of the broken ball end. Then the moment of truth! I pulled the trigger and used minimal pressure for less then a couple of seconds and stopped to check whether I was hitting the center of the ball end and drilling the center point. It was over! There was a neat hole perfectly centered on the object. A couple of quick blasts of electrical cleaner (most use naptha as the main ingredient) cleared the shavings. I then used a 9/64″ drill bit, once again marking it for depth, as I didn’t want to drill into the back of the nut. Less than two seconds on the trigger did the trick. Then cleaned shavings out of the nut again. Next, I made an extractor out of 1/8″ high speed steel. I sharpened the end to a point and circumscribed grooves across the point. I tapped the extractor into the hole of the ball end. It held quite firmly but alas…….could not pull the ball end out after much manipulation. The ball end was mangled as such that it would not align with the hex nut sides and the extractor kept slipping. After a moment of thought I decided to Jerry Rosa it and went for it! I put a 1/8″ high speed steel black oxide bit in the drill and aligned the jig once again, being sure that it rotated freely, marked the bit and applied a drop of oil. I pulled the trigger again for two seconds and it was over. The ball end was turned into shavings with no damage to the sides of the hex nut. I disassembled the jig and tried a hex wrench at full depth. Worked great! I think this can be used in differing configurations. I hope this helps all you repair people!
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2 Replies
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This is really cool. That drill jig is a fantastic idea.
Center drills, or spotting drills, man when my machinist friend told me about those is was a real game changer. No more bridge pin holes on custom bridges where the bottom of the hole was in a different spot that the top of the hole.
Thanks for sharing.
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Slick move. What a clever setup, well done!
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