There is a lot of conflicting info on this topic.
I found this on the net some time ago now, and for me it's very useful:
QUOTE
If after lowering the strings, the notes buzz only above the 12th fret, then there's too much bow in the neck. You'll need to tighten the truss rod.
If after you lower the strings, the notes only buzz in the 1st 5 frets then your neck is too straight. You'll need to loosen the truss rod.
If after you lower the strings, the notes buzz all up and down the neck, the neck's fine. Your strings are just too low.
UNQUOTE
Using this, I aim at getting the neck as straight as I can (with the strings retuned to pitch after each adjustment to the truss rod) and then set string height to about 3/32" at the 12th, consistent with no buzz up and down the neck but, if there happens to be any buzz at the first few frets then I add relief till it goes away.
My J Bass neck is set up with paper thickness relief at the 5th while depressing the E at the 1st and 12th frets...measured in play position. I can hardly see a gap...I can only hear a pinking noise when tapping the string over the 5th.
Some necks wont adjust perfectly straight (ie when the strings have been retuned to pitch)...as is the case with my Sting Ray...so I adjust it as straight as it will go and leave it at that...making sure, of course that there's no buzzing on the first 4 or 5 frets. Relief is about .008"
(Without string tension I can get straightness...even a back bow).
The way I see it IMO is that there is no pre-determined dial-in truss adjustment which is going to be ideal for all players. The amount of relief, to avoid buzzing at the first few frets, will vary for each player, depending on how he/she plays. I've heard of guys using up to .025".
There's also conflicting information concerning where neck relief should be measured!
A luthier advised me that the most effect the truss rod has on the neck is at the 5th or 6th fret and that it has no effect on the neck past the point where the neck meets the body. I'm not a luthier so I can't state whether that's wright or wrong.
What I do is to depress the 1st fret with the left hand. With the right, I depress the 12th with my thumb and have the middle finger pointing in the direction of the headstock and use that finger to check the relief at the 5th (or 6th, depending where the greater distance is between the bottom of the string and the top of the fret). After adjusting necks for a time, you get to know, by feel, what the approx. measurement is. As I said above, paper thickness is about right for me...if I can get the neck that straight. The actual distance can be measured with a feeler gauge and, to make things easier, a capo on the first fret.
I check relief in the play position....seated with Bass on lap. If measurements are made with the Bass laying flat on a bench then gravity is going to come into the equation as well..when you pick it up to play they will be different.
RIDER TO THE ABOVE. This is only my way of going about it. I'm not saying it the right way.
