Truss rod nut--what's normal?

[dinosaurneil]

Hello,

New (paranoid) guy here wondering what the nut should look like from the outside. I bought a 2005 MIA P bass and the setup seems fine, but I was taking a look at the truss rod nut out of curiosity. There appears to be a bit of jagged metal on the inside edges of the nut.

I didn't get a wrench in the purchase so I've ordered one since I figured just making sure the nut turns with the appropriate amount of tension is one test. Is it possible this appearance is somewhat normal? Thanks!

[NCD]

NOT a Luthier myself but I have more experience with allen screws than any normal human should. That said...

If there is jagged metal in the hex hole of a truss rod it's an indication that someone tried to adjust it with an allen wrench that was a little too small and slipped a few times as they used it. I'm a tech who used to work on automated assembly lines that were almost entirely put together with allen heads, which allowed us techs to do most anything with just a set of allens in our pocket.

If you never, ever use too small of a wrench again then the allen hole may be okay in the future but if you ever get ANY sign of slippage then stop immediately and take it to a real pro to get that puppy replaced while there is still some grip left in it. The pro may need that remaining grip in order to work on it. Once it strips out completely you may have a real mess on your hands if removing a truss rod with a stripped head is anything like removing our allen screws once they stripped.

Could we get an experienced Luthier to chime in here?

[dinosaurneil]

Thanks for the response! I've ordered the Fender red handled "T" wrench and don't plan on doing any adjusting other than if it really needs it. Other than a single mark (as if the too small wrench had gouged the side of the nut) the surfaces seem to be in good shape.

If I wanted to just go get the nut replaced, any idea how much that would cost?

[NCD]

I honestly don't know... best to direct that one to a Luthier. My experience is with all kinds of allen headed hardware and hard experience has taught me that the instant you have slippage with the right size tool in there then that's the time to replace the screw/bolt whatever. This is because once it's all slip and no grip you usually end up with a nightmare on your hands when you try to get the old one out of wherever it's at.

Now this may or may not hold true for a truss rod. For all I know a Luthier may easily be able to swap it out even if it's completely stripped... but would you want to strip it completely and take that chance?

In my world it took several carbide bits and an easy out to remove a screw... even more carbide bits to drill one all the way out or 4 dremel disks to cut the head off. Do you really want any of these tools near your bass?

Not me buddy!

Oh, just a useless fact for an FYI. Never try to drill out a hardened, high grade bolt or screw with titanium bits. The grade of steel in the bolt will make a mockery of the titanium bits, dull them and then once they get dull people press too hard. This causes the titanium bit to snap while at high speed in the drill, making the broken tip into a missile. At my old work the one time we took safety goggle with a deadly seriousness was when drilling out a bolt and we never allowed anyone within 25 feet of the person drilling.

It took 3 people getting "shot" with broken bit tips to get us to enact those rules. Low grade bolts are easy to deal with but the high grade hardware can be a real hazard to try to cut out.

[Pilgrim]

I'm not a luthier, but from the photo it doesn't look to me like there's any damage. The sides of the hex recess look clean and straight from what I can see. If the wrench fits fully into the recess, nice and tight with no slop or movement, I'd say you're good. Just make sure you can get it as deep into the recess as it's supposed to go.

If it hangs up with minimal travel into the recess, or you can twist it gently and feel it moving around inside the recess, stop there and re-think what you're doing. In that case, you at least need to try some other sizes of hex key.

[georgestrings]

Originally Posted by Pilgrim

I'm not a luthier, but from the photo it doesn't look to me like there's any damage. The sides of the hex recess look clean and straight from what I can see. If the wrench fits fully into the recess, nice and tight with no slop or movement, I'd say you're good. Just make sure you can get it as deep into the recess as it's supposed to go.

If it hangs up with minimal travel into the recess, or you can twist it gently and feel it moving around inside the recess, stop there and re-think what you're doing. In that case, you at least need to try some other sizes of hex key.

+1 to this, and will add that it should be a 3/16" allen key - the type with the bondus ball on the end...


- georgestrings

[T-Bird]

Hi.

Judging by the pic, it seems that the TR nut in Your bass is in an exeptionally good shape, so no worries there.

Engineering folks who deal only with machinery, don't usually come across punched allen slots, they're either cast, forged or machined. The teachings in Poly. are also usually long forgotten .

TR allen nuts are punched for several reasons, mainly because it's the cheapest mfg method and the material allows it. It's a good thing that the TR nut material is deliberately chosen to be rather soft, softer than the TR anyway, so in the unavoidable eventual event of the threads deforming, the deforming takes place on the easily replaceable nut threads, not on the TR threads.
If it was designed in the other way round, or the hardnesses were equal, stripped threads would mean TR replacement in 95% of the cases. And we don't want that, now do we?

Another positive side of a soft TR nut is that a damaged one can be easily removed by re-punching the slot with an appropriate tool.



The "chips" or "pieces of jagged metal" OP sees in there are the punched in shavings that the tool removes when it forms the allen slot. Absolutely nothing to be worried about.

Regards
Sam

[NCD]

Sounds like excellent news for the OP! In that case, the correct tool shouldn't slip in the head of the bolt at all.

Just as a general practice, as soon as a screw or bolt start stripping out in the head OR threads in any way, replace it. This is for anything, not just musical instruments. The reason I say that is that people often try to use that last bit of grip to get whatever tightening done that they want at that moment but they are't realizing that this is the very mistake that can often make replacing the damaged hardware a royal pain in the (censored).

I'm glad that the OP seems to have one less thing to worry about!

[dinosaurneil]

Originally Posted by T-Bird

Hi.

Judging by the pic, it seems that the TR nut in Your bass is in an exeptionally good shape, so no worries there.

Engineering folks who deal only with machinery, don't usually come across punched allen slots, they're either cast, forged or machined. The teachings in Poly. are also usually long forgotten .

TR allen nuts are punched for several reasons, mainly because it's the cheapest mfg method and the material allows it. It's a good thing that the TR nut material is deliberately chosen to be rather soft, softer than the TR anyway, so in the unavoidable eventual event of the threads deforming, the deforming takes place on the easily replaceable nut threads, not on the TR threads.
If it was designed in the other way round, or the hardnesses were equal, stripped threads would mean TR replacement in 95% of the cases. And we don't want that, now do we?

Another positive side of a soft TR nut is that a damaged one can be easily removed by re-punching the slot with an appropriate tool.

The "chips" or "pieces of jagged metal" OP sees in there are the punched in shavings that the tool removes when it forms the allen slot. Absolutely nothing to be worried about.

Regards
Sam

That's a relief! I figured I just didn't know enough to understand what I was looking at. Great explanation. Thanks!