Height of saddle above bridge

[Dale Penrose]

What is the max height of the saddle above the bridge. I'm looking at .325 inches. Is my neck angle too great?

[Michael Lewis]

The ideal string height above the surface of the top (soundboard) at the bridge is about 1/2" (13mm). The amount of saddle showing above the top of the bridge is not so relevant except for stressing the saddle so much that it breaks, and yours is rather tall in that respect.

[Arnt Rian]

I agree with Michael. Assuming you are talking about a "normal" steel string guitar bridge, I like the saddle to protrude about 3-4 mm over the a 8-9 mm bridge. A string height over the soundboard at the bridge location of about 12 mm or so works well. I will sometimes adjust the size of the bridge for a specific weight, and in order to keep the string height over sound board at the optimal height, the height of saddle showing above the bridge will be adjusted accordingly, but no more than about 5 mm for my bridges. Much higher than that, and the stress on the bridge becomes too high for my liking. With traditional "through saddles", such as on the vintage Martin, Gibson etc., the risk that the front of the bridge will split off increases with a taller saddle.

[Joe Lanza]

.325" is pretty high, but if it's a brand new guitar, you might want to wait a few weeks and see if the geometry changes. Especially if you are in a place with high summer humidity.

[Todd Stock]

In a nutshell, probably - assuming your bridge thickness is between close to where it should be and your string height over the top is not insanely high with the current neck set.

How thick is the bridge at the thickest point (usually between the A and D)? What is the current action at 12th and 1st frets...preferably to the .001" or 0.1mm? What is the D string height over the top just in front of the bridge?

If you are shooting for a string height of .500" over the top at the saddle, your bridge should be a minimum of .320" and a max of about .360" between the A and D (for a radiused top bridge like a Martin), giving a saddle height above bridge of .140"-.180". Anything over that may be problematic, depending on the design of the bridge.

Whether your existing bridge support a saddle higher than .180" above the bridge depends on the bridge design. As Arnt mentioned, through saddles are more prone to blow out due to their reduced support, which is why most luthiers glue them in place. However, even drop-in saddles can blow out if there is poor stock selection...think of a bridge with grain that looks like a smile or a frown, and you have an almost guaranteed blowout for a traditional Martin belly or Martin/Gibson rectangular bridge. A saddle slot that is too shallow with a very high saddle is likewise going to be problematic.

My rules of thumb are:

- Target string height above top of .500" (000/SJ or larger), .525" (00 and 0), and .550" (smaller than 0)

- Max saddle height above bridge after stringing of .200" (which will usually decrease in the first six months by .020"-.030" for my instruments)

- Slot depth of at least desired saddle height above bridge, but usually about 1/4" on drop-in saddles (thru saddles made to traditional patterns are another story...they get glued in with hide, and I never exceed .180" height, and shoot for a max of .150")

- Slot setback from treble side of bridge of .160" minimum (.180" is better, but looks wonky on traditional thru saddles...if not a slave to tradition, go .200 back if it's your bridge design) and very straight grain that is no worse than parallel to the slot on the treble said of the bridge.

I usually end up with .180" saddle height with a .350" thick bridge at string-up and a drop to .500" within six months (usually after a week or so on larger bodies and a little longer on small bodies...longest to settle in was a Size 5 that took 6 months to drop to .540 final height), and a slot depth of 1/4" on a drop in. I just had my second commission back in after 8 years and string height over top was .490" with a .340" thick bridge.

Some other things to consider:

- Thickness of under-saddle pickup (some will run close to 1/16", but the DTAR and LR Baggs flexible versions are about .030-.035, so add that to desired slot depth

- Your bridge may simply be too thin for the desired string height above the top. For your current neck set, try seeing where your fret line passes over the saddle location...should be 1/32"-1/16" above the top of the bridge (higher for larger body; lower for a small body). If you have a .250" thick bridge on the guitar at present, and your saddle height is as stated, swapping out the bridge for one of correct thickness (e.g., .350") would give you a .225" saddle height....still higher than desired, but likely to drop to .195" -.200" after a month or three as the guitar stretches and settles in. Still more stress on the bridge and saddle than desired, but you can probably live with it.

- If the bridge is anywhere close to the .320"-.360" thickness mark, time to reset the neck. Refit such that with the fretboard well leveled, you have that 1/16" or so of clearance over the bridge (sans saddle). This is just a rule of thumb...some instruments will distort quite a bit under tension and other (think Guild Westerly 12 strings) won't move at all.

- New builders tend to set things up a bit on the high side to address issues with fret geometry, relief, etc. - in other words, look at your fret work and setup carefully. I had a new builder in showing off his pride and joy, and like you, the saddle was pretty high. Once we did some remedial fret cleanup, dropped the 1st fret action down to something reasonable, adjusted relief from nil to .006", and adjusted the action at the 12th to .100"/.075" (he's a flat picker with pretty aggressive attack), saddle height came down to about .180", which was just about perfect for a newly strung instrument.

[Rodger Knox]

If the saddle is leaned back the height above the bridge is less problematic.
The "optimum" angle is half the break angle, so that the saddle bisects the break angle. That eliminates any force on the sides of the saddle slot. Since the break angle varies from string to string, determining the "optimum" angle is more trouble than it's worth, and I typically use 6°. I've read that 6° is about right to automatically take care of intonation adjustments due to changes in action height (ie higher action needs more compensation).

[Alan Carruth]

I've been using a nine degree back angle, which Rick Turner says is the 'best' for intonation. Whatever: the important thing is to tip the saddle back at least some.

[Rodger Knox]

I guess I better check my bridge slotting jig. I was pretty sure I got the 6° from one of Alan's posts.

[Todd Stock]

I've used up to 11 degrees on tilted saddles, and shift in intonation point is correctable on the saddle itself even at higher angles assuming an feasible vertical adjustment range of .150" or less. String height above the fretboard is invariant, so just the scale length change of around .030" to contend with, and that is doable on a modern thicker saddle.

Not a cure...assuming a 30 degree average break angle, a 6-7 degree tilt will reduce out-of-axis forces quite a bit, but there's still out-of axis load on the saddle (and bridge) left, dependent on break angle, so planning for good support and avoiding excessive saddle height remains a concern.

[Murray MacLeod]

My rules of thumb are:

Target string height above top of .500" (000/SJ or larger), .525" (00 and 0), and .550" (smaller than 0)

Hi Todd, I find it interesting that you advocate a higher string height as the body size decreases.

My preconception was that as the soundboard size decreases, and as the bracing gets lighter, it takes correspondingly less torque to drive the top, so that the reverse would actually be the case, ie the target string height would drop as the guitar gets smaller.

I am fully prepared to be educated on this point, however, and would really appreciate it if you could perhaps expand some on the reasons why I am mistaken.

[Todd Stock]

Smaller bodies deflect less under the same loads, despite the lighter bracing and thinner top used by some builders. Given that the practical limits on string height above top are structural in nature (deflection, versus strength limited), the higher we can push the string height, the more energy we can push into the system. We already know that sensible volume and projection are tied to body volume and top area (e.g., a short scale dread will almost always be louder and have greater projection than an 0), so up to the point where the system cannot accept more energy without detrimental effect, increasing string height will buy back some of the volume and projection lost with reduction in body volume and top area as size shrinks. Why not .6 or .7? Because I don't believe that the extra brace depth or top thickness increase to alleviate long-term distortion trades evenly with the additional increment in energy available to the system. Bottom line: I want to maximize string height without requiring increases in bracing depth or top thickness that reduce responsiveness

And besides...anything much beyond .550-.6 begins to look pretty wonky.

[Alan Carruth]

Murray McLeod wrote:
"My preconception was that as the soundboard size decreases, and as the bracing gets lighter, it takes correspondingly less torque to drive the top, so that the reverse would actually be the case, ie the target string height would drop as the guitar gets smaller."

You have to remember that it's not the torque that is the primary driver. I have data, including listening tests, that shows that people can hear a difference in the sound when the string are higher off the top, but measurements show that there's no more power being produced. What changes is the mix of partials. Since the tension change signal that torques the bridge is frequency doubled compared with the string fundamental, what you get with a taller saddle is more of the second partial, and maybe a bit more of some higher even-order partials as well. There's also another motion of the string up around the 7th or 8th partial, that can drive the top more easily with a higher saddle, but it's not putting in a lot of power. After all, there's only so much power in a plucked string, and if it comes out one way it can't come out in another.

Todd's right in saying that the soundboard gets stiffer as the span is made smaller, assuming the same structural sizes and so on. You can either lighten up on the structure a little and get more responsiveness, or make the bridge taller and get a somewhat different sound.

[Todd Stock]

That is a great insight, Alan, WRT the relative volume of the partials versus fundamental with string height above top...when I build small guitar, I'm not looking for a huge bottom end and a big boom-chuck, so the chime that I'm after in a high-strung Size 5 would benefit from the higher string height whether sensibly more powerful or not. Pretty much agrees with what I have seen with Size 0 and smaller stuff, and especially Size 5's.

I use lighter bracing as body size goes from Grand Aud or dread down to 00...but once I'm at 1/4" x 1/2" and about .105, I start getting more concerned with brace print-through and maintaining enough gluing area to keep the brace on and handle reasonable shocks, so while cross section and the degree of scallop/taper are useful to control stiffness, using softer tops (Engelmann and softer Lutz and Euro are set aside for the little guys in my shop) is as important once down around 0 and smaller.

One thing to consider is that deflection of a beam under load is a function of the cube of the length, so minor reduction in brace length or body length/width has a bigger effect on top deformations than we might assume...a brace that allows a 1/16" deflection over 18" of length would allow just half of that with just a 20% reduction in length, so we can trade reductions in deflections due to the smaller body against reductions in top thickness and brace stiffness due to cross-section until the point where we need to start thinking about brace print-through and long term permanent deformation under constant load.

[Alan Carruth]

Todd Stock wrote:
"One thing to consider is that deflection of a beam under load is a function of the cube of the length, so minor reduction in brace length or body length/width has a bigger effect on top deformations than we might assume."

Right; and it's deflection of the top that ultimately matters. Bernard Richardson pointed out in a paper in the Catgut 'Journal' that it's the Area/mass ratio of the soundboard that determines how much power the guitar can put out. As you make the outline larger you have to beef up the top thickness and bracing to control the deflection, and the mass goes up faster than the area. That's one reason why it's easier to make a loud small guitar than a loud big one (although 'loudness' and 'power' are not really the same thing...).