Neck shim - How to estimate the correct angle?

[Alex_C]

I'm building a partscaster and I'm having an issue with neck angle. I get pinging at the upper register.
I shimmed the front of the neck with a Stew-Mac .25 degree shim. It made it better but not perfect. I've been down this road and usually keep trying different things until it feels right. I'm wondering if there is a better method vs trial and error. I have some idea's but I'd rather get some feedback from experienced users.

 

[Musekatcher]

I can give you the geometry to calculate an angle, and estimate the increase in action at the 12/20 fret for a shim between the two body screws, but IME you have to trial and error. Neck shape before and after stringing changes from wood to wood enough, that if you want the lowest action without fret contact, you are dealing in thousands of an inch at the fret - the shim thickness will be a fraction of that, too small to work with normal toolry. I just pulled a Squier neck off to shim and surprise, it had a tiny shim piece between the body screws!

 

[SRHmusic]

I second a trial and error approach. I bought a few from Stew Mac and tried them (0.25, 0.5 and 1.0mm). The geometry is not really simple, depends on knowing bridge height relative to the neck, etc. and a small error can result in a shim change... But if someone has a fairly robust method for these measurements I'm all ears.

 

[Allan Allan]

Cut up a Business card. You don't need the stumac $10 woodscrap

 

[Jimclarke100]

All the books say draw it out at full scale side on...

 

[schmee]

From bridge to nut the string is a straight line. Shimming only helps to give you more/less bridge height adjustment. That's it.

If you are fretting out somewhere check:
String height too low
Truss rod relief
Your frets with a fret rocker.

 

[SRHmusic]

From bridge to nut the string is a straight line. Shimming only helps to give you more/less bridge height adjustment. That's it.

If you are fretting out somewhere check:
String height too low
Truss rod relief
Your frets with a fret rocker.

That's good to point out. Neck angle adjustments are only needed if you don't like the bridge (or saddle) height or run out of range. Any other issues are probably setup/leveling/etc. issues unless the neck is warped or something.

(Also, I like the StewMac shims or similar because they keep full contact between the neck and bottom of the pocket.)

 

[Alex_C]

From bridge to nut the string is a straight line. Shimming only helps to give you more/less bridge height adjustment. That's it.

If you are fretting out somewhere check:
String height too low
Truss rod relief
Your frets with a fret rocker.

Thanks, but it is neck angle. A flat shim in the pocket will do as you mentioned. An angled shim will either raise the high frets or lower the high frets, relative to the string.
That is what these are for: (link removed)

 

[tah1962]

Cut up a Business card. You don't need the stumac $10 woodscrap

+1...This past weekend I worked on a ‘10 American Standard Strat for my son’s friend. The neck needed shimmed and I cut a business card in half and it worked perfect. I also made a very slight adjustment to the truss rod. The action is great now with absolutely no fret buzz.

 

[Alex_C]

I should mention that I've built over a dozen partscasters and worked on dozens of guitars. I'm not a noob, but I was hoping to decrease the time spent getting a perfect setup.

 

[Alex_C]

Cut up a Business card. You don't need the stumac $10 woodscrap

I've done that in the past. I've also used brass shims, I had a bunch of different thicknesses. I may go back to paper to get the micro adjustment I need.

 

[Alex_C]

(Also, I like the StewMac shims or similar because they keep full contact between the neck and bottom of the pocket.)

I'm using the StewMac shims, this guitar needs the thicker end pointed away from the bridge. Unfortunately, the .25 is a bit more than I need. I may end up using paper.

 

[BryMelvin]

I can give you the geometry to calculate an angle, and estimate the increase in action at the 12/20 fret for a shim between the two body screws, but IME you have to trial and error. Neck shape before and after stringing changes from wood to wood enough, that if you want the lowest action without fret contact, you are dealing in thousands of an inch at the fret - the shim thickness will be a fraction of that, too small to work with normal toolry. I just pulled a Squier neck off to shim and surprise, it had a tiny shim piece between the body screws!

Use the same technique you would setting up neck or saddle on an acoustic. use a straight edge down the neck and shim till you get the approximate height at the saddle area of the body. Of course you'll be shimming instead of cutting a saddle or fileing a dovetail.

 

[schmee]

Thanks, but it is neck angle. A flat shim in the pocket will do as you mentioned. An angled shim will either raise the high frets or lower the high frets, relative to the string.
That is what these are for: (link removed)

Right? I think of the body as just an extension of the neck. You could beuild a guitar that had no body, just a neck extending to the bridge location.! Now if you could move the bridge closer to the end of the fretboard somehow....

 

[schmee]

The body-less guitar! Bad logic?

 

[Musekatcher]

Use the same technique you would setting up neck or saddle on an acoustic. use a straight edge down the neck and shim till you get the approximate height at the saddle area of the body. Of course you'll be shimming instead of cutting a saddle or fileing a dovetail.

Yes, that's a better technique, I'll clamp a level over the frets, and block and clamp at the saddle to fit, and measure for a shim. As far as the math, if you ignore the relief (which is faulty), the math is relatively simple. Straight edge across the frets to the saddles, determine the over/under hieght you want corrected. Multiply that by fret location/scale length. So for a narrow shim under the 20th fret on a 25.5" scale, shim = x*17.468/25.5, or x*.685. If you measured .020 too low at the saddle (high action), you'd need a shim = .020*.685 = .014 to lower it by .020 at the saddle, and correspondingly lower to the frets.

But then, this brings up the real issue, which is the relief. If you pitch the neck with a shim, you aren't pitching a flat fretboard, you are pitching a curved fretboard. Imagine if you increase the shim till the strings touch the last fret, you still have space at the 12th fret. This is usually the problem, where the action at the higher frets, say fret 15 and above, the fretboard is closer to the strings than at the 12th, and the break angle isn't enough over each fret, to avoid hitting the next higher fret. So, for a given relief in a neck, there is an optimum saddle hieght, that keeps the string/neck break angle at all frets sufficient, so it won't buzz. Sometimes, this results in higher action that folks like.

If you take all the relief out of the neck, you will still get some relief after its tuned to pitch. if you add backbow to compensate so that you have a flat fretboard after its tuned, you end up with very low action (too low) in the lowest frets, and high action (too high) on the upper frets.

Now imagine moving the neck pocket down by routing it out, but without changing the neck angle. And imagine adding flat shims to raise the neck without changing the angle. Location of the pocket plane, AND the neck angle are equal factors. Most folks miss the pocket location, which can be slightly wrong on off brands, or can be nullified by a replacement neck that hasn't been shaved to the right thickness for the pocket plane, etc.

The right relief is a big deal, and a great feature in the fretted instrument world. But the other factors are just as important, some easier to adjust, some harder to adjust or not adjustable, such as on an acoustic. Proper relief, at the right angle, at the right joint plane, and the right saddle height is invaluable. Just some things to think about, if you find yourself chasing action, relief, and buzzing in a circle.

 

[Fender-guy]

As mentioned before, a neck shim is really only needed if the saddles are maxed out up or down.

Look at the pics above, if your saddles are right where they should be and you’re added a shim to the front of the neck pocket, you’re actually raising the trouble frets.

I’d set the neck relief at almost zero relief, set your action at the saddles and then the nut. If you have high action with the saddles as low as possible then you need a shim.

If you have the strings laying on the frets with the saddles all the way up then you need a full even neck shim since the neck pocket would be too deep.

I’ve never in my life needed a neck shim if I can get perfect action without buzzing and maxed out saddles. You probably have something else going on like high/low frets, bowed neck, etc

 

[jrblue]

IME you have to trial and error.
So true. You may calculate what you think would and should work, but compression of the shim itself, among other variables, makes even careful figuring a diceroll. I always have a bunch of shims at hand, and never want to settle for somethjing that is not exactly right just because it's what I have on hand. Getting that neck angle dialed in is a pain in the rear, until you nail it, and then you're happy indeed because suddenly everything feels freaking great! Makes a big difference, IMO.

 

[Alex_C]

Right? I think of the body as just an extension of the neck. You could beuild a guitar that had no body, just a neck extending to the bridge location.! Now if you could move the bridge closer to the end of the fretboard somehow....

The graphic is odd with the angled neck because it raises the bridge. If the bridge is lowered, where would the string touch first? The first fret or the last fret?
I drew a green line to explain my situation better, Yes, it is exaggerated, but you can see that the higher frets would touch first.

 

[Fender-guy]

It’s going to be hard to get any kind of advise without some more info. So you say you get pinging at the upper register, so the first 8 or so frets or the last 13 to 22 or so? Stupid question but people do get yet terms confused, upper frets being closer to the pickups not the nut.

Also what is you neck relief set at and what is your saddle height and action right now?

Another thing is, you put a shim in the front section of the neck pocket. Looking at the pic, that would point the headstock upwards.