Broke the ball end off my 1/8th Truss key in My National

[alisterhrae]

While straightening the neck on my National M2. The ‘ball end’ of my hex key snapped off and is stuck in the truss rod? I have tried everything to get it out but it’s in tight? Do any of you fine folks have any experience with a similar problem?

[snakehips]

Hi there !

Is it wedged in there but moving, or is it stuck fast ?

Do you have any super strong Neodymium magnets that might pull it out ???

An Allen Key shouldn't break - so either it was a v cheap one (poor quality steel) and/or what the hell were you doing to your guitar to break the Allen key ????

[alisterhrae]

Thanks Snakehips, I’ve tried the magnets, tried fine metal pointed tools like Dentists use, just can’t move it. It was a Stew Mac 1/8th tool. The ball end just snapped off! Ball ends are clearly not a good idea? I’m just wondering if I can drill it? How do I post a picture?

[leeophonic]

I would think drill and tap it, probably using a dremel size drill with the extension flexi shaft, tape well around the headstock just in case you slip.

Extreme fix would be to weld some sort of rod on the end but would anticipate the drilling to be sufficient with some sort of bolt or screw in place try to use a tool similar to a slide hammer although smaller.

You would also be advised to email NRP & Stew mac and let them know of the tool fail and see if there are alternative solutions.

Good luck.

Lee

[neilm]

Ive had this happen to me...not on a guitar thank god.....i used a good quality super glue and acivator...just use a small drop on a suitable tool and press it carefully to the ball end then spray with activator......i bit of gentle `wiggling` and it popped out. IMO Ball end allen keys are only any good for actually fitting a bolt into place...as soon as there is any force switch to a normal allen key.

[Stevie]

It shouldn't have broken because the short crank handle deliberately minimises the torque you can sensibly achieve with finger and thumb. It's why the ball end is never at the short end. When tightening cap head bolts at structural split-lines inside "mouseholes" on aircraft galleys, we frequently used ratchet ring spanners over ball end Allen keys and these devices were never intended to be abused like that, yet I don't recall ever seeing one break off, so I would definitely query Stewmac over this.

It probably broke because they are hardened (well at least case hardened) to help keep from rounding off the corners in use, and that starts to introduce brittleness. It's a trade off between resistance to wear and torsional strength. Being hardened means that attempts to drill will theoretically be fruitless, and will likely result with the drill bit scooting off into the wood because you would at the very least need a long series drill bit because otherwise the rotating chuck will mar the guitar, and long series drills are very much harder to control. Even a centre dot starting point will be difficult to achieve. Ask anyone who has broken off 6-32 taps in blind holes in aluminium blocks- it's a nightmare! (Although fair enough- a tap is likely to be harder still than a ball end allen key.)

Try tapping with a centre dot eccentrically in the opposite rotation to that when it broke. You need to direct the point at an angle and towards the outside edge of the ball end and use a "toffee hammer" (no more than four ounce). This is very difficult to do and carries the obvious risk of slipping off the edge of the broken ball end. I would make this my very last choice.

I am reluctant to make suggestions like this because I've endured some horror stories in the past at work, and anyway- we can't see how far down the broken off end is to make ideas objective.

There are ways to attempt bonding a mandrel onto the broken off ball end with a suitable adhesive such as Araldite (NOT "Kwikset" or "Rapid") and waiting patiently for a full 24 hours before attempting to turn it the opposite way to what you were attempting when the breakage occurred. There's a better than even chance that the adhesive will fail anyway. That path is fraught with perils which is why I have twice deleted a detailed description of a possible method ...

Grind off with a Dremel or snap off the short end of the broken Allen key (protect your eyes- cover it in rag and whack it in a vice) As a by-now straight piece of hexagon rod, this will fit into a drill chuck securely and will vibrate nicely against the broken ball end. Drill a hole through a piece of metal bar to slip over the hexagon bar tool and use it with your other hand to guide the work. Use lots of surrounding protection. All you should be doing there is trying to vibrate it free from where it is presently jammed. As suggested, a neodymium magnet should then be able to extract it.

Good luck, but rather you than me Gungha Din.

e&oe ...

[pete1951]

Jul 13, 2021 0:02:22 GMT Stevie said:

Good luck, but rather you than me Gungha Din.

e&oe ...

Very hard to add anything to stevie’s answer . It would be good to know just how deep the hex key hole is. If it is significantly deeper than the length of the ball end , it might be possible to push the ballend deeper and adjust the truss rod with a standard key. It’s probably that NRP have had this happen before and have a solution.
Pete

[snakehips]

Oooh !

Just had a thought.
Follows on from the discussion about broken tailpieces.

It might be possible IF the is a clear line of sight, and you can get access to someone who has one :

Laser-weld the allen key hand back onto the ball (ideally laser weld as much as you can see), then attempt to pull the allen key in the popposite direction to where you were going when it broke.

I think laser welding IF you can get good aim, would work well. It would give a stronger bond potentially, than glues etc.
I'd expect little collateral damage, if you can protect the wood around the rod - laser-welding causes very little heat close to where you are welding.

Just a thought !

[Bo Grohl]

What about injecting a freezing liquid (e.g. nitrogen) or dropping dry ice onto it to see if that contracts the ball by a fraction?
TT

[Stevie]

I thought of that too TT but held back because you can't really control what the jet of (probably solvent based) fluid is going to do to the surrounding timber and more importantly the finish. It's a decent idea though.

e&oe ...

[pete1951]

Or, a very hot hex key pressed against the broken end. If more heat gets into the outer sleeve it may drop out.

Most truss rods these days are 2 way, and the adjustment nut is often trapped inside a tube, I am not sure of NRP design there are several types of 2 way rod. A drawing of it might help , anyone know what type they use?
Pete


The red rod is a StewMac one and has an 1/8 hex key ( much smaller than the 4mm of the other 2 Far Eastern ones)
the hole on this example is about 3/8” deep, the ball end would be just over 1/8”, there may be 3/16 of ‘meat’ for a standard hex key to turn the rod IF the ball end will push in .
Your rod may not allow this to happen, and pushing the broken ball end even deeper is the very last thing to do!
Pete.

ps: if you go down this road, use a new hex key and possibly grind the end square so there are no rounded corners, the end of the hex key could even have a small hole drilled in it , to let the key get as deep as possible around the broken ball end ( the key will probably be as hard as most drill bits so this may not be an option unless you have some engineering skill/tools)