Purpose of Neck Shims?

[JacoNOT]

If these questions are considered "hijacking", somebody say so and I'll start my own seperate thread. Hey, KingRazor: I figure this thread kinda already ran it's course (fisticuffs and everything ), and the OP (you) is now "shimmed to perfection" so I hope you don't mind...

Break angle is the angle of the string from the saddle to the tailpiece...also the angle of the string from the nut to tuning peg.

Not enough break angle at the nut sometimes causes the string to rattle in the nut...exacerbated by lack of witness point. Break angle is easy to change at the nut.

Not enough break angle at the saddle can lead to occasional buzzing at the bridge. Witness point is also important here. One piece bridges make it impossible to change the break angle at the bridge. The exception is a bridge that allows top mount or string-through options. AHA!

It was once thought that increasing break angle would increase string tension. It does not.

It is sometimes suggested that changing the break angle significantly changes tone....it is purely subjective.

Thanks 202dy. Primum non nocere. I'm hip.

Based on your excellent treatise, my follow-up question just has to be: What does "WITNESS POINT" mean? Is it the specific highpoint atop nut or saddle where the string actually bends / changes direction?

Q2: How do you alter break angle at the nut? File a steeper angle in the bottom of the string slot - to make sure the string breaks exactly at the front face of the nut?

Q3: My bridge allows for string-thru-body as well as top mount. The bass is new and I'm a new bassist. The stock strings are strung through the body, and I'm having a devil of a time figuring out where the buzz is occurring. It very well could be at the bridge. Can you (or anybody here) tell me what to look for to get a handle on this?

Thanks, and I beg your pardon, KR.

 

[JLS]

Can somebody give a solid definition for "BREAK ANGLE"?

I'm going back-and-forth between adjusting neck relief, then saddle heights - trying to come up with a lower, buzzless action on my LTD 5-string. I'm sure it doesn't need shimming, but I feel like I'm missing something...and maybe the key is to understand BREAK ANGLE and exactly what a correct break angle is.

What you're missing: a fret level/recrown, done at pitch, with the strings on.

 

[96tbird]

Witness point: a clear and defined change of angle over a stop point. Press the string on both sides of said point with thumbs to create a Sharp bend in the core of the string.

Q2: file the nut at a steeper angle than the break angle. I mark the fret side of the slot with a point of a sharpie in the bottom of the slot. This will make sure I don't remove material from the contact point. A few quick passes in the slot with a needle file and done. Lube the slot by rubbing a pencil lead in there for smooth tuning.

Q3: first make sure all saddles are level with the deck; but different heights reflecting the arc of the fret board. Make sure saddles aren't buzzing on one another.

 

[JacoNOT]

What you're missing: a fret level/recrown, done at pitch, with the strings on.

I read you loud and clear. That's how I've figured it, up to now. I started a thread HERE asking for recommendations for good preofessional setup in my locale. No responses. Dead as a doornail so far...(crickets chirping)

 

[JacoNOT]

Witness point: a clear and defined change of angle over a stop point.

Q2: file the nut at a steeper angle than the break angle.

Q3: first make sure all saddles are level with the deck; but different heights reflecting the arc of the fret board. Make sure saddles aren't buzzing on one another.

96T ==
Thanks for the clarifications. Looks like I came pretty close on "witness point" based solely on the context in this thread. I chopped up your comments for the quotes, but I understand and appreciate every word. Good tips.

I'll take an extra hard look at the saddles. I attempted to level each one relative to the deck, but they're very close to one another. It's entirely possible that two (or more) might be canted just enough to touch-and-buzz (I had a girlfriend like that once )

Another question: My strings are run thru-body at present. The thru holes are located about 1/2" forward (toward headstock) of the surface-mount holes in the rear plate of the bridge. So the thru-body BREAK ANGLE is very steep - much steeper than it would be with strings run through the typical surface-mount holes. So the question is (finally): There's no way that my current thru-body mount could be a case of not enough break angle, right?

 

[SLaPiNFuNK]

You have to force the break angle over the saddles.

I see many pictures of basses on here where there is no witness point over the saddles.

Now, depending on the strings you are using they may our may not be flexible enough for through body stringing. Although you would know that right away because they would simply break.

 

[mongo2]

Another question: My strings are run thru-body at present. The thru holes are located about 1/2" forward (toward headstock) of the surface-mount holes in the rear plate of the bridge. So the thru-body BREAK ANGLE is very steep - much steeper than it would be with strings run through the typical surface-mount holes. So the question is (finally): There's no way that my current thru-body mount could be a case of not enough break angle, right?

IME, yes. Your break angle from the saddle to the string anchor is pretty much at it's maximum for a given saddle height using the thru-body string anchors.

You may have to push down each string a couple of inches in front of the saddles (neck side) to create a good witness point at the saddle. I usually push down each string several times. You'll probably have to retune after you do that.