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Question to get a Picture good string action

Posted: Wed Apr 19, 2017 9:54 pm
by chan2000
I'm thinking nut to saddle to fretboard is a triangle so to use trigonometry to figure out picture of good string action of 2mm to 2.5mm
From john, bridge and saddle height is about 0.5 inch. String length or nut to saddle is either 25.4 in or 24.9 in
Because that's scale length

Neck tilts at 14th fret but a neck bows when stringed.

And at 12th fret is the half of scale length

And i dont know the nut depth. And i have to measure height of fretboard and fret

Am i including all the elements to get picture of good string action?
Does this look correct?

Re: Question to get a Picture good string action

Posted: Thu Apr 20, 2017 6:42 am
by tippie53
at the nut you want the bottom of the nut slot to be about .007 in off the top of the 1st fret. When you fret the 3rd fret the string should just be off the 1st fret.
your best way to figure this out is to just take a sacrificial nut , and keep taking measurements till you start buzzing but first I do this

capo the 1st fret then I can check all my adjust my reliefe
to check relief I want to fret at the 13th and my string height off the 6th fret should be about .004 in between the fret and string.

that way you know your neck relief is good
next I want to check action height. you can do this by checking the height at the 13th fret since your fretted on the 1st
in inches
2/32 off the high E
and 3/32 off the low E
this is a good starting point.
we are assuming you have leveled and dressed your frets first.

now take the capo off and you can adjust the cut slots
again this is a sacrificial nut and you can take the nut slot to the point where it will start to buzz. Now you know for sure where you cannot go.
you can now shim that nut or make another one.
It isn't that hard but it is good to take it to the point of buzzing so you learn what it looks like and the measurements so you get the best set up you can,

Re: Question to get a Picture good string action

Posted: Fri Jun 16, 2017 11:49 am
by chan2000
I measured my $100 mitchell guitar and drew a picture of the measurements

Re: Question to get a Picture good string action

Posted: Fri Jun 16, 2017 8:39 pm
by Diane Kauffmds
Good string action is everything John said. I would add that the best action is that which the owner/player is most comfortable.

Martin's standard action on new guitars is 3/32" on bass E, and 2/32" on treble e. That's their formula for "one size fits all". It's a good comfortable action for a guitar built for someone else. However, some of us like our action higher or lower. For instance, I prefer my action to be as low as possible. So, my best action is 1/2 to 2/3 of Martin. I adjust my bass e to 3/64 to 2/32", and treble e at 3/64". The strings are just high enough that there is no buzz. My fretboard and frets have to be meticulously leveled to achieve this.

Re: Question to get a Picture good string action

Posted: Sat Jun 17, 2017 6:30 am
by chan2000
I see neck bowing when you string the guitar is a problem to the action of a guitar.
bowing makes action a little higher.

if neck is straight line then a parallel line to point where string sit on at the nut, and the height where that parallel line's point at the saddle and where string sits on the saddle is twice the measurement of the action since the action is at the half of the scale length.

because neck bows, I guess the neck is little tilted to downward.
is neck tilted about 1.5 degree downward?
John's video mention using 28" sanding disk for the body to get 1.5 degree downward

Re: Question to get a Picture good string action

Posted: Sat Jun 17, 2017 7:33 am
by Danl8
Chan2000,
The neck joint obviously serves a couple of purposes, not the least of which is to raise the strings off the table (soundboard) for playability without raising the action or fiddling with fingerboard geometry. As the instrument ages, this also helps to prevent bowing which would lower the saddle height too much. The sides can be flat but tapered to the plane of the fingerboard above the sound-hole. Neck relief is all about matching the curvature of the fingerboard to the amplitude of the vibrating string to minimize fret strikes/buzzing. This can be done with the truss/fret tension or by shaping the fingerboard in trussless instruments. On really old instruments this was accomplished by tapering the gauge of the tied-on gut frets and tapering the FB.

Using John Hall's formulae make good sense; I do and my results have been most satisfactory. Remember Diane's comment about fine tuning to your individual needs; the best set up is the one for your personal preferences.

Re: Question to get a Picture good string action

Posted: Sat Jun 17, 2017 9:37 am
by chan2000
Besides neck bowing, I guess not all guitar necks are bowing the same way..
some bows little more than the other, and that little amount makes difference in action.
ideally neck and FB is a straight line, but it isn't

Re: Question to get a Picture good string action

Posted: Sat Jun 17, 2017 10:01 am
by Danl8
chan2000 wrote:...ideally neck and FB is a straight line, but it isn't
yes, it should start out that way. My kit guitar was initially straight, but bent more under tension than I expected resulting in too much relief. That neck is closer to balsa wood than proper cedar. The truss rod has been able to bring it back enough to be playable.