Twist in the neck - how to spot?

Littlejonny · June 2023

This Fazley guitar I bought recently - I levelled and crowned the frets and they do feel good now. I also put a little shim in the neck to get the angle to the bridge better. I tried lowering the nut slots with some cheap files but I’ve f*cked it up and although the depth is good the slots are too wide and there’s some ‘pinging’ when I bend the g and b strings. So the next thing to learn is how to remove the nut entirely and install a new one. This is all fine because I bought the guitar as a cheap experimenter and I’m learning…

there is a problem in slightly worried about though: the relief on the treble side of the neck seems less than on the bass side. Probably half the distance between string and 8th fret with the 1st and 22nd frets pressed down.

Is this a sign of a twisted neck or more likely something else, or even something I’ve done?

Many thanks

Funkfingers · June 2023

Neck relief depends to some extent on what string gauges you use. On a budget instrument, it is possible that the sub-optimal woods and truss rod might fail to do their job.

A vibrato bridge can contribute to action/relief set-up problems.

BillDL · June 2023

This seems like an opportune time to ask @ICBM about something he mentioned quite a while ago. Apparently when tightening the truss rod the neck can be pushed into a slight twist. From memory of ICBM's post I think this was because of the friction of the truss rod nut against the washer on Gibson style truss rods, but I honestly cannot remember exactly what it was he described.

Did you straighten out the neck using the truss rod so that it was flat before you levelled the frets, or did you just remove the strings (and neck if a bolt-on) and level it? It is good practice to make sure the neck is straight using a notched straightedge before levelling the frets. If you remove the strings the neck can go into a back-bow because the truss rod has been tightened to counteract the string tension. If you level the frets like that you will be taking off too much metal from the frets in the centre of the neck and not as much from the ends, and when you then string it up and it goes into natural relief you may have too much relief that you cannot address by tightening the truss rod.

What did you use to level the frets? If you used a long flat sanding beam beam with abrasive paper that allowed you to do long strokes while moving across the width of the fretboard with each pass, there can sometimes be a tendency to take more material off the frets at one or both sides or more in the middle. It takes a good bit of practice. If you used a radiused sanding block it is quite easy to lean harder on one side or hold it more across to one side.

How does the guitar actually play if you ignore the pinging at the nut? Having slightly less relief on the treble side can actually be beneficial, and very skilled luthiers are able to do clever fret work where they deliberately create a difference in relief across the board.

The pinging in the nut slot when you bend the string is likely to be from a miniscule ridge at the bottom of the slot that catches the string and then releases it through the bend. You can normally get rid of it by folding over some fine wet & dry paper twice so you have a slightly round-edged crease and passing it gently back and forward through the slot.

stickyfiddle · June 2023

Just fyi on the nut - pinging means the slots are too narrow, not too wide.

It’s actually very rare for slots to be too wide unless the string is literally able to move laterally in the slot.

What you want is a nice semicircle shape at the bottom of the slot, a little bit wider than the relevant string. Then tension will naturally keep the string in the bottom of the slot

DavidR · June 2023

Best way to view a twist in the neck is to put the instrument on a stand and then sight down the neck from above. This contracts the view of the neck and exaggerates to the eye any twisting. (Pretty good way to actually 'see' action too.)

ICBM · June 2023

More relief on the bass side than the treble is normal and good - within reason - as it allows a lower action on the treble side and less rattling on the bass side at the same time.

As BillDL said, it's often caused by the truss rod - a conventional rod has a nut which is tightened against a plate, and there is considerable friction between the two. As the nut is tightened clockwise, the friction locks in an anticlockwise twisting force on the neck, which if the adjuster is at the headstock end will produce more relief on the bass side.

As stickyfiddle said, the nut slots *should* actually be wider than the string, and if shaped correctly - with a rounded bottom, not flat (or worse, triangular which will cause binding) - the string will self-centre and move freely, even if the slot is a lot wider than the string.

BillDL · June 2023

@DavidR mentioned sighting down the neck. With a skilled eye you can generally detect twists and sometimes other irregularities, but I've always found that the shape of the nut (generally taller on the bass side) and the bridge (again usually higher on the bass side) deceives my eye into thinking there may be a twist, and I have to try and deliberately ignore the nut and bridge/saddles while sighting a neck.

WezV · June 2023

I've lost the ability to sight down a guitar neck with my dominant eye, thanks to a damaged retina making everything look squiffy. I can still just about do it with my left eye, but it doesn't come as naturally.

Anyway, the main point is that not all twists are fatal - see what can be done in set-up and fretwork. If it is significant, you can try a heat treatment to straighten, but wood will still do what it wants.

Littlejonny · June 2023

Thank you all so much for the replies.

I did straighten the neck using a notched straight edge before levelling with a radiused sanding block.

but it could be that I put more pressure on the bass side, although I wasn’t aware of doing this.

I can’t sight a twist in the neck - but it is a cheap guitar so maybe the wood has been twisted a little when I did the truss rod.

the not slots are definitely wide. There is also definitely ridges in the as described.

BillDL · June 2023

I have a pretty good quality but budget priced "SG" style guitar with a fairly slim neck that used to creak slightly when I tightened the truss rod and I could see it twisting the neck ever so slightly by watching the headstock from that end while I had tension on the truss rod nut. It always returned to flat again when I released the tension on the rod, but the creak was a bit disconcerting. I removed the nut and smeared some lip salve on the back of the nut and thread. It lessened the creak but the neck still twists the tiniest amount while I have tension on the nut.

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Twist in the neck - how to spot?

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