Making a nut for a guitar is not the simplest thing to do. However, string widths vary with the preferences of the player. One can purchase a one-size-fits-all plastic nut and hope it works. Hope is not a strategy.
The first thing that one needs to do is to decide on the width of the nut. The finished width of the fretboard at the nut will be the same dimension (43 mm is common).
The width between the center of the 'E' string and the center of the 'e' string must also be fixed. Woody uses 36 mm for this dimension. The rest of the strings are evenly spaced between the first and sixth string centers.
To lay out these string centers, put the bone blank in a small vise with good light. With a sharp pencil mark all of the string centers on top of the bone blank.
Then put the nut blank in the clean slot at the end of the fretboard. Draw an arc on the face of the nut 0.060"- 0.070" above the fretboard. This arc should be parallel to the radius of the fretboard. Use a 0.060" spacer and a light gauge pencil (0.5 mm works well). This arc will determine the bottom of the string slots.
Lastly, the top of the nut is rounded and smoothed. The final depth of the string slot should be half the diameter of the string. This will keep the string from creating a buzz as the open string rattles back and forth between the walls of a deep groove.
Something like this:
Of course, by the time one gets to setting up the guitar, the neck angle should have long-ago been set. There are several remedies if the neck angle is incorrect after the fretboard is in place... none of them are easy but if you would like an explanation of how to re-set the neck angle on a guitar, Woody is glad to help. Email: Woody@Woodystrings.com
Check out Woody's July 2019 Luthier's Journal for details.
The gauge is only about 3" long and tapers from one end to the other. The scratch lines across the gauge mark the thickness of the brass at 0.060", 0.070", 0.080", 0.095" and 0.100" thickness (right to left). The heavy part on the left end is the 'handle'.
Woody uses this gauge to measure the distance between the string and the 12th fret (0.095") and the distance between the fretboard and the string at the 1st fret (0.060"). All else aside, and light gauge strings on the guitar, these target dimension produce a nice, low action on an acoustic guitar.
Pictured below is a gauge that I made (about 40 years ago) from a scrap piece of brass . It has served me well.
3/4 Dreadnaught Dimensions
With a dovetail joining the neck to the body, the proper neck angle is set during construction and assembly of the guitar. Without the fretboard on the arm of the guitar, a straightedge should be 3-4 mm above the soundboard at the point where the saddle will be located. On a 14-fret dreadnought with a 25.4" scale, the saddle will be approximately 300 mm from the 14th fret. 3-4 mm straightedge clearance above the soundboard at the saddle will create the proper* neck angle between the arm and the body.
*The proper neck angle will depend on the soundboard radius; the desired bridge thickness (8.5 mm); and the height of the saddle above the bridge. In Woody's case this would be a 30 ft. soundboard radius; approximately 8.5 - 9.5mm bridge thickness; and 4 mm of saddle height above the bridge surface.
The Finishing Process for spraying, cutting and polishing with nitro cellulose lacquer is broken down into nine steps explained in Woody's July 2019 Luthier's Journal.
String Vibration Briefly Explained
Journal Sept 2018
String Compensation Briefly Explained
Journal Sept 2018
Laminate Necks, Home-Shop Method
Journal Sept 2018
Woody has a lot of explaining yet to do...
one bite at a time.
See you next month.
wJs Headstock Inlay
This has become Woody's standard peghead inlay. An introduction to the process involved in this inlay has been presented in Woody Strings December 2018 Luthier's Journal. A couple of clicks on the navigation bar above will get you there (same as it got you here).
The eventual final set up of the guitar will depend on the player's preferences and style of play. The height of action, the string width at the nut, the string width at the saddle, radius of the fretboard, gauge of strings, etc. impact the set up. Any guitar that one buys from a music store should be set up to suit the style of the player.
Likewise, any dimensions mentioned here would be impacted by the player's preferences. Woody sets up a new guitar to an average that has worked for several decades of building and repairing guitars. Keep in mind that every part of the action is in continuous flux, mainly due to the weather, but also due to the player's preferences (which also change over time).
Flame Maple Back and Cutaway
Woody, as one might expect, would prefer to have the beauty of wood speak for itself. Lately, I have acquired some interesting maple stock that can enhance any guitar design. Three examples are shown in the photos below.
The fret saws pictured above are various thickness (kerf) and all cut on the pull stroke, Japanese style. They are very controllable.
Note: For years Woody cut all of the string slots with one 0.025" back saw. By rocking the angle of the blade from left to right, one can widen the string slot as necessary.
The nut files pictured here are handy in that they cut a different width on each side of the file. They add even more control when one wants to cut the final depth of the string slot without going too deep. Woody tries to keep the bottom of the string slot at 0.060" above the fretboard. A fretboard radius line drawn on the nut blank helps in this regard.
Woody's cutaway process is explained in the Luthier's Journal for March 2019.
0.060" at the 1st fret
(string to fretboard)
3/4 Dreadnaught Dimensions
Set ups (not sit ups)
August saw a lot of string-up/ set-up activity. There are eight guitars being built in the shop right now. Five of these are finished and were set up in August.
0.095" at the 12th
(string to top of fret)
A line across the top of the frets should not be straight but should form an arc to accommodate the path of the string. A two-way truss rod is the most convenient way to bend the neck so that the fret line forms this arc. A perfectly straigt neck will buzz at the first few frets if there is not proper relief.
A way to check the relief is to place a straight edge on top of the frets and slide it toward the nut (as Woody is doing in the photo). At the fourth or third fret one should feel a little bump as the forward corner of the straightedge bumps the fret. Same at the second fret. Same at the first fret.
One should not have to see the straight edge bump up the frets. The bumps can be felt in a steel straight edge and heard if one is listening.
Making the Nut by Hand from a Bone Blank
Woody checking the neck relief.
wJs String Clearance Gauge
Simply stated, Neck Relief is necessary because the strings on a guitar vibrate in an arc. The oscillations are wider in the center of the string (12th fret) than at the ends (nut and saddle). This should be obvious to anyone who has jumped rope.
Finally, all that I want to say right now about this 3/4 dreadnaught is that it is fun to make and it has been very popular. I plan to make a few more.
A discussion of string vibration, string compensation and laminate necks will have to wait until next month.