bridge spring spacing vs neck taper/width

[Brian Evans]

When I set up the guitars I built, I set the bridge spacing so that the outside strings were a fairly constant distance from the edge of the neck - about 1/8" - following the taper of the neck. I just noticed that on at least one of my "bought" guitars the strings taper less far out than they could - they start around 1/8" at the nut and at the 12th fret are close to 3/16" to 1/4" in from the edge of the neck. The two guitars I am looking at (haven't done an exhaustive study of the herd) both have 1.75" nuts and very close to the same string spacing at the nut, but the bridge string spacing is almost 1/4" different - plus the guitar with the narrower string spacing at the bridge actually has a wider neck at the 12th fret. I just noticed this, and it all seems very odd to me. What is your practice with string spacing compared to the edge of the neck?

Brian

[Chuck Tweedy]

I shoot for 3/16" from the edge at the 12th fret. This is required to give the fingers clearance to get around the high e string as the string action rises off the board.
On the bass side, you need to keep the low E string from being pushed off the board.

If you have C&N, it gives very specific dimensions which work quite well.

[Alain Lambert]

What Chuck said. Also the string spacing at the bridge varies typically from 2 1/8 to 2 1/4 depending if the guitar is for strumming or fingerstyle. Fingerstyle being generally 2 3/16-2 1/4

[Murray MacLeod]

A formula which works well is that the string spacing at the bridge should equal the fretboard width at the 12th fret. This determines the taper automatically.

IMO If the string spacing equals the fretboard width at the 11th fret it is even better.

[Chuck Tweedy]

I urge caution in using the string spacing at bridge = board with at 12th rule-of-thumb!!!
It is not always true - In particular when making a custom instrument with non-standard nut-width and scale length.
If the strings run closer to parallel than on a standard layout, the board will be to narrow - this can lead to a very expensive mistake - DAMHIK ... Oye!!

Just measure-twice-cut-once

[Todd Stock]

Martin seems to have worked this out over the last 180 or so years - they provide scale length, nut width, 12th fret width, and pin spacing for all of their guitars, which is a pretty broad range...pick a winner and duplicate, and your margins should be adequate because Martin is generally more generous in added width at 12th than some other makes.

Common arrangements:

Generic: 1-3/4 nut, 2-1/4 12th, 2-5/16" pins
Bluegrass fav: 1-11/16" nut, 2-1/8" 12th & pins
Short scale 12 fretter w/14 fret body (ala Norman Blake): 1-13/16" nut, 2-5/16" 12th, 2-3/8" nut
12 Fret: 1-7/8" nut, 2-5/16" 12th and pins

Al of these combos maintain decent clearance at the edges of the board, so a place to start. Otherwise, draw things out full size for the guitar under development and compare to a full size drawing of the measured arrangement for a guitar you find acceptable.

For common scale lengths, you can always riff off the vanilla 1.75" nut/2.25" 12th/2.31" pins that seems to work for many Martins...tweak the 12th fret width by 1/2 the change at nut or pins and fudge to maintain the margins at the 18th, 19th, or 20th with pin spread increases, then draw it out. I set E2 in at nut by .125 and E4 by .100 for most players, and I like the 3/16" number for the 12th, but if you have a guitar that is very comfy for you or your customer, duplicate the layout.

Once again - if in doubt, draw it out ACCURATELY and compare to a layout that works for you.

[Brian Evans]

So the consensus is that maintaining a fairly equal string to edge of neck spacing is less correct that arranging things so the strings taper in towards the bridge more than the neck does. I can see why, the strings are easier to bend and pull off the edge in the middle of their length. Oddly, as a player I think I prefer the other way, with the strings an equal distance. Since it's an archtop, easy to change and I've been planning to make a heavy bridge for that instrument anyway, when I do I can try a slightly narrower string spacing at the bridge. Equally I can make new bridge inserts for the other instrument, and widen it out a bit, since the string taper on it really seems excessively narrow at the bridge. It is a spider cone resonator guitar.

[Murray MacLeod]

Martin seems to have worked this out over the last 180 or so years - they provide scale length, nut width, 12th fret width, and pin spacing for all of their guitars, which is a pretty broad range...pick a winner and duplicate, and your margins should be adequate because Martin is generally more generous in added width at 12th than some other makes.

Worth pointing out that Martin only started providing the 12th fret width dimension within the last 18 months or so ... I like to think that the constant hammering away on the AGF for the previous five or six years about the importance of this measurement by both Larry Pattis and myself was instrumental in persuading them to disclose the info.

As Todd says, Martin do provide a more generous taper, which unfortunately is all too often negated by their appalling fret end beveling, which removes far too much real estate from the top of the frets.

[Clay Schaeffer]

If you use the neck width at the twelvth fret to determine the pin width at the bridge the outside strings will maintain the same distance from the edge of the fretboard as they have at the nut. It is simple geometry.

[Murray MacLeod]

If you use the neck width at the twelvth fret to determine the pin width at the bridge the outside strings will maintain the same distance from the edge of the fretboard as they have at the nut. It is simple geometry.

You might want to revise your geometrical calculations, Clay.

[Dave Weir]

I picture all the strings and the edge of the board converging at one point. So the E's get a little farther from the edge as you go up, but not very much. I think they are moving away from the edge at the same rate they are moving away from each other.
25" scale, 1.75" at the zero fret. String spread is are 1.5" and 2 1/16" at the bridge.

[Eric Knapp]

This thread made me go back and measure my reference guitar. I had assumed the distance from the outer strings to the edge of the fingerboard was the same everywhere, but it is not. I was just about to cut a fingerboard and the fret slots and now I am back to the drawing board, so to speak. This is a good time to discover this rather than just after I cut everything.

Thanks!

-Eric

[Clay Schaeffer]

D'oh!
You're right Murray, but the practical difference is rather small.

[Todd Stock]

Worth pointing out that Martin only started providing the 12th fret width dimension within the last 18 months or so ...

As Todd says, Martin do provide a more generous taper, which unfortunately is all too often negated by their appalling fret end beveling, which removes far too much real estate from the top of the frets.

IIRC, Martin provided the nut, 12th, and bridge info in their very complete specs through the first major revision of their web site back around 2009-10 (?) or at least I was able to find it without issue. Then some idiot web designer got rid of all the important, useful info in the first revision. The second major revision of the site, which is fairly recent (as mentioned, within the last two years), makes you dig for the info, but it is there. The legacy site design was a little messy, but did a great job of archiving older models, specs, articles, etc. - the newer site designs have been awful. Try searching the site for 'Norman Blake' and see what comes back...

Agree on Martin fret work - there's no good reason for the skin-flint fret height and rolled fret ends...Martin has bumped the height up recently to Taylor spec (still too low), but they still have the PLEK machines set up to produce a mediocre job on new guitars. Often the best solution for players is to bite off on a refret to get workable height/width/shape, durable fret material (EVO or stainless), and fret ends that are not ramped. Always fun to have a guy walk in with a 'stage-ready' GPC that still gets a $350 refret, $400 pickup system to replace the overly complex, prone-to-failure Fishman, and $135 worth of saddle & bridge work before it's road-worthy.

[Doug Shaker]

Todd,

I would be interested to hear what your specs for a road-worthy fretboard.

[Todd Stock]

Pretty much covered it...the constant radius 16" goes to a lightly compounded 16" to 20" (think old Martin refretted several times), stainless set in hot hide glue and .045" with revised crown shape, 35 degree end bevel and no 'ramp' at ends. Clients that were burning through the factory frets in a year or so of 6-8 shows a week get a 'forever' board. Nut and saddle revised (new radius and material on saddle; excess trimmed on nut), bridge ramped and slotted, pins swapped for more durable, consistent plastic, bone, or ebony.

Just not sure why - in this age of PLEK and assembly line robotics - we're not offering a 'vintage' board that mimics the subtle compounding of vintage Martins, the durability of stainless or EVO, and some choice in height/width/crown on the frets. Just working a board without the use of a fixed radius block naturally provides some compounding, and it's hard to believe that CNC cannot reproduce the effect.

If Mario wanders in, ask him - he went to stainless years ago and I've never had a Proulx in the shop that was not super comfortable to play.

[Murray MacLeod]

Todd, could you clarify what you mean by "ramped" fret ends ?

I associate "ramping" with sanding in a fallaway on the fretboard extension, but that doesn't seem to be what you are referring to ?

[Barry Daniels]

Yeah, I was wondering about that too. I decided that he must mean overly rounded fret ends like you see on some Fender necks.

[Todd Stock]

What Barry said - a large-radius curve applied at ends of fret along length versus clean, crisp angle with properly eased sharp edges. Both Gibson and Fender used to do this, and I see it on some refrets that come in for correction.