Action - How low can I go?

[Doug Collins]

I keep reading that good action measures about 3/32" under the 12th fret. I can't seem to get my guitar to play without buzzing at less than 4/32". 

My neck angle seems correct with a straight edge just touching the top of the bridge. Neck relief is as much as possible and there are no high frets that I can find with my rocker tool.

 

Is there any other factor that I am ignoring? 

 

When I tighten the truss rod to reduce the relief, thus lower the action as well, a buzz occurs somewhere above the 5th fret (toward the body).  I am afraid to lower the saddle any more for fear of buzzing. If I do, and buzzing occurs, I'm guessing loosening the truss rod might correct it, but won't that just raise the action again?

 

Thanks,

 

Doug Collins

[Mark McLean]

Hi Doug

Getting perfect low action without buzzing - the holy grail of the acoustic guitar!  How is the action at the nut?  If you find that the action feels a lot better with a capo on the first or second fret then you want to pay some attention to the nut.  Here is a good overview by Frank on that important factor.

http://www.frets.com/FRETSPages/Musician/GenSetup/NutAction/nutacti...

 

Another important factor is string tension - which is affected by string gague, type, scale length and tuning.  Have you tried different string types?

 

You say that the neck angle is good with a straightedge resting on the bridge?  Is that when the guitar is under string tension, or before you strung it up?  If it was before, it often changes as the strings pull the bridge up and rotate it a bit forward. 

Good luck with it

Mark

[Doug Collins]

Hi Mark,

 

Thanks for your reply.  I think the action is pretty good at the nut.  I did use Frank's advice on this.  I so far have only tried one gauge of string (12-53). Perhaps I could try a heavy gauge, but I can't help to think I still need to work on the set up.

 

The neck angle was measured without tension.  Under tension the ruler does not quite clear the bridge.  What is the correct way to measure this?

 

Thanks,

 

Doug

[Doug Collins]

I realize my subject title is the "million dollar" question. Perhaps I need to ask it differently.

 

My next course of action would be to lower the saddle height at the risk of introducing a buzz.  I may then be able to lose the buzz by
adjusting the truss rod, but I suspect that just puts me back to where
I started with high action. 

My new question is: Does lowering the action by tightening the truss rod yield the same result as lowering the saddle?

 

Right now if I tighten the truss rod, thus lowering the action, I get a buzz.  Can I most certainly expect the same if I lower the saddle by the same degree?

 

Thanks,

 

Doug

[Mark McLean]

Heavier strings will raise the action further and make playability worse - they need to be tighter for the same pitch.  I was thinking of going to lighter, or softer (silk and steel) strings if you want more playability. 

 

The truss rod is for adjusting neck relief, not action (although it has a slight indirect effect.  The action is detirmined by the saddle (and nut).  So I would go down with the saddle, then readjust for correct relief.  I don't think you will be back to square one.  Whatever height you take off the bottom of the saddle - the action at the 12th will reduce by half that amount.  Don't be afraid to play around with saddle height.  You can always shim it back up again (or drop a new one in there). 

 

Regarding neck angle - many people set it so that the straightedge is a bit high of the bridge initially, so that it is level under string tension.  It depends on how stiff your top is and how heavily braced.  If it is heavy it won't move much anyway, but a lightly braced top can be a very different shape after you string it up. 

m

[Doug Collins]

Thanks Mark, you are very helpful.

 

I will have a go at the saddle.  The only reason why I am hesitant to do so is because it is a wider than normal saddle, and if I go too far I will have to order a new one and have to pay shipping charges.

 

I didn't think shimming it would be considered "good practice", but if you feel it is acceptable, I have to ask what material would you use?

 

Thanks,

 

Doug

[Jeff Highland]

You are going about it the wrong way.

The order you do things matters and some of these things may make the problem seem worse, but work through to the end.

First tighten the truss rod to give a low relief. I aim for about 6-8 thousands of an inch

(holding the string to the first and 14th frets and measuring clearance at the middle)

This will undoughtedly make the buzz worse, that is to be expected.

Now check the nut slots depth by holding each string down between the 2nd and third frets and checking the clearance over the first. It should be about the thickness of a sheet of paper.

Finally, adjust the saddle height, It is probably going to be too low now on yours, so shim it for now till it is perfect and then make a new saddle to that height..

Of course all this assumes that your frets are in good shape.

[Doug Collins]

Hi Jeff,

Your procedure makes sense to me. I wish I had read it before I further reduced the saddle height. But I'm still a little unclear about the truss rod relief.  Is 6-8 thousands what I want for a final setup? In Frank's article on truss rod adjustment, http://www.frets.com/FRETSPages/Luthier/Technique/Setup/BuzzDiagnos...
he talks about low relief at 10 thousands.

Should I expect to have to add a bit of relief once I have an acceptable saddle height?

 

Thanks for your help,

 

Doug Collins

[Jeff Highland]

There are differing opinions on the desirable amount of relief

To me 10 thou is the maximum unless I am compensating for uneven worn frets (where the owner does not want to pay for a fret dress).

I set the relief  and then move on to the next step and use the saddle height to set action.

Going back and changing the relief leaves you chasing your tail

 

[Doug Collins]

Jeff,

I have taken your advice and tightened the truss so that I am at your maximum of 10 thousandth.  Without doing anything further to the saddle, my string height at the 12th fret is now an ideal 3/32th.  However, I have a buzz from the 4th to 6th fret on the low strings.

What is your recommended next step, assuming the frets are level, and I believe they are. Do I add relief or raise the saddle height and accept higher action?

Thanks,

Doug

[Jeff Highland]

Have You checked the nut height?

Problems in the 4-6 area does indicate to me a fret level problem.

Have a look closely at the string to next fret clearance as you fret in that area.

Adding relief is not the answer here.

You may need to look at a fret dress or just add a l/16 shim under the saddle to give more clearance, You may just be aiming for too low an actiion for your playing style.

 

 

[Pierre-Antoine Roiron]

You may just be aiming for too low an actiion for your playing style.

Jeff is pointing out a good one : you have to consider this possibility too.

[Pierre-Antoine Roiron]

I have a different approach of the set-up process. Depending on the guitar, your playing , tuning, string gauge, sound looked after, etc... you can have very different set-ups. I don't measure relief or string height to decide if it's good or not, or only by eyeball. Set-up is good if it suits your needs.

Sometimes, a set-up can be hard to perform. I use this rule : if it's buzzing on the first frets, I tend to loosen the trussrod. If it buzzing everywhere, I try to raise the saddle. If it's buzzing only on the higher frets (above 5th or 7th), I try to raise the saddle and tighten the trussrod. Sometimes, you need to make a lot of tries. I consider that performing a good set-up is finding the good balance between saddle height and relief.