Sire U5 Truss Rod Nut

[OldNARDGuy]

Picked up a very briefly and lightly used U5. It's near mint, and I like everything about it.
BUT... the seller didn't have a truss rod hex key. No problem, I've got a tool box, right? Sire tells me me it should be 4mm, but my 4mm Stanley hex key is very loose, maybe having a 1/2 inch 'wobble' at the long end when inserted, which is way too loose for my comfort, so I'm not about to try to turn the nut. The nut appears to be in good shape, I don't think it's been rounded out ( see lousy pic attached ). If I can find a 4.5mm locally I might try it.
Anybody else have this issue?
Maybe I should just take it in to a luthier?

 

[Matt Liebenau]

4mm could be the right size and is a pretty typical hex key size on imported basses. Not all 4mm hex keys are equal however. A 4mm from a different branded set or even another set from the same brand could be a better fit. If it’s possible to try a couple of 4mm hex keys that might be the thing to do.

 

[timmus]

I’ve found that Bondhus Allen wrenches seem to fit these fine. They can be had on Amazon and a metric set is about $15

 

[MuseChaser]

The truss rod nut on my Peavey Grind5 was abused by a previous owner. It's ostensibly a 4mm, but it's been rounded off a bit. I've found that I can still adjust it by wrapping the end of my best fitting 4mm hex with a layer or two of aluminum foil, taking all of the tension of the strings, and applying pressure on the neck in the direction I want it to bend while carefully turning the nut.

 

[badgrandad]

There actually have been several people who have had problems with the truss rod nut being loose fitting, myself included. So much so that there is a thread about people taking a 4.5 or bigger hex and grinding a taper to it so it wedged tight ( which is what I did). Some have recommended epoxying a star drive bit into the end and using a socket type truss rod tool to adjust.
I ended up having to buy a new neck.