Nuts and Saddles
Nuts and saddles are key components to any instrument. Making sure they're in good condition and get replaced when necessary will help keep the guitar playing at its best.
The Nuts and Bolts of....Nuts
The nut of the guitar establishes the string distance from the edges of the fingerboard as well as the spacing from one string to the other. Perhaps even more critical is the distance of the strings above the frets. Many factories will leave the slots a little on the high side so when it gets shipped to a different climate and the neck moves it will still be playable. However, the higher the strings are above the frets the more difficult it is to play especially in the first position. On the flip side, if the slots wear and become too low the strings start to buzz on the first fret when played open. Even a few thousandths of an inch can turn "good" in to "great" and of course "good" can go "bad".
The slots of the nut should be cut properly to allow the string to ring from the very front edge next to the fingerboard. If a slot is cut poorly or has worn over time the instrument might have some intonation problems. If the slots are worn or poorly cut, the excessive friction can cause the string to bind up in the slot. Listen for any metallic "pinging" sounds as you tune. This could indicate the string is binding up in the slot or perhaps on a string tree. Another helpful tuning tip is to always tune the string UP to the note and not down to the note. If there's any excess friction and you tune down to the note it might bind slightly and as soon as you pick or bend the string it will slip in the slot and be out of tune again. Many times over the years someone brought me their guitar because they want new "better" tuning machines only to find out the slots are worn and can benefit from a slight filing. This is not a DIY project in my opinion because one too many passes with the file and the slot will be too deep causing the string to buzz on the frets.
There are many factors that go into that thin light colored material on your acoustic guitar bridge. The curvature along the top where the strings press will create the "feel" across the neck matching the curvature of the fingerboard. Also the bass side (Low E) is slightly higher than the treble side (High e) and this establishes the "action" of the guitar. The action is a term for how the strings are set in relationship to the frets.
The next detail to be aware of is how well the saddle fits the slot. There is a width the slot and a length to the slot. With modern instruments and the advent of CNC machining these details can be pretty well standardized during manufacturing. However depending on the price point of the instrument even modern CNC production can leave lot to be desired. The saddle should fit the slot in such a way that it doesn't lean under the pressure of the strings. When you change the strings take a minute to check how well the saddle fits the slot.
- With a finger on the top of the saddle try to wiggle it side to side. The direction I'm referring to is towards the neck and away from the neck. If it does in fact wiggle turn the guitar upside down and see if the saddle falls out. Before you actually do it also be on the look out for anything else that falls out of the slot! Perhaps it has a shim underneath the saddle and you wouldn't want to lose that.
- If it does fall out consider having a new one made somewhere down the road. It likely isn't an emergency but could be a way to avoid some damage in the wood over time. It's also a nice upgrade in terms of playability and tone. If you're guitar doesn't have a pickup and you would eventually like to have one get both done at the same time for the best result.
- If the saddle doesn't fall out of the slot take a close look at the wood around the saddle. Are there any hairline cracks near the ends? Don't confuse the pores of the wood with cracks. More than likely everything will be fine but it's worth a glance at the very least.
Another small detail that can make a difference in how everything works together is "coupling". When you pluck or strum your guitar the strings are set into motion and that vibrating mechanical energy is transmitted through the saddle, to the bridge and to the top. The top vibrates and this moves the air inside the guitar body which exits the sound hole and is picked up by our ears as sound. Now...the bottom edge of the saddle should fit perfectly to the bottom of the saddle slot to efficiently transmit this energy. It's always something I check when installing a pickup element in the saddle slot. Every time an instrument comes to me for a saddle replacement I always make it a point to flatten the bottom of the slot and fit the new saddle perfectly to the slot. This way each string is ensured it's energy isn't lost by small gaps between the saddle and the wood.
The might be the wrong time to bring this up but the physical location of the saddle in relation to the neck is critical. I bring this up last because I assume the vast majority of the instruments will be right but not all instruments will have this right. If the saddle is slightly too far forward (towards the neck) or too far back (away from the neck) the guitar will not play in tune. It is not the hardest repair in the world but at the same time the process is no easy task. Essentially wood is fit the same way a new saddle would be but then it's glued in place. I've simplified this for to save time but it's a job for a luthier to be sure.