How To Shim A Neck

[7string]

Yup, it's those airpockets which, over time, can introduce moisture into the neck, swell it and create a "rising tongue".

Making a ladder of shims which tapers is an alternative for those who don't have the facilities to cut wod (like me!).

[Jus Lukin]

-

Edited February 16, 2022 by Jus Lukin

[Guest BassKS]

[quote name='BigRedX' post='503121' date='Jun 1 2009, 05:57 PM']Last time this question came up I did a couple of diagrams showing how various neck adjustments affected the action:





IMO this topic should really be added to the Wiki rather than stickying it.[/quote]


OK.... So I got this warmoth Jazz from the States while I was out there... It was put together ok but I just cant seem to bend the strings in the high frets. The strings hit the fretboard and die out. No bluesy solo.... The action is indeed low but increasing it may solve the bending string prob but not neccessarily make it easy for me to play the rest of the bass (Slapping etc). The neck has zero relief.
Do I relieve it first, or will the shim take care of everything (as per diagrams indicating that the relief is zero should you choose to put the shim)...

Help,

[BOD2]

[quote name='BassKS' post='974861' date='Oct 2 2010, 11:56 AM']OK.... So I got this warmoth Jazz from the States while I was out there... It was put together ok but I just cant seem to bend the strings in the high frets. The strings hit the fretboard and die out. No bluesy solo.... The action is indeed low but increasing it may solve the bending string prob but not neccessarily make it easy for me to play the rest of the bass (Slapping etc). The neck has zero relief.
Do I relieve it first, or will the shim take care of everything (as per diagrams indicating that the relief is zero should you choose to put the shim)...

Help,[/quote]


Neck relief has most effect on frets around the centre part of the neck. It's not so likely to stop fretting out on the higher frets as there isn't much neck left in that area. If you are having problems in the high frets then you'll probably have to raise the action. Try adjusting (raising) the action before attempting to do anything with neck shims.

[Nostromo]

[quote name='BOD2' post='496312' date='May 23 2009, 08:51 PM']A shim place at the back of the neck pocket (as described above) will change the neck to body angle by effectively pushing the headstock backwards. This has the effect of lowering the action.

A shim placed at the front of the neck pocket (furthest away from the body) will effectively push the headstock forward and should slightly raise the action.


Thanks for reading this - I hope someone finds this useful. [/quote]

Great thread . . . thanks . . .

But I could do with a bit more advice ? . . . can anyone advise the thickness of Shim needed to achieve a specific amount of height change in the action ?

This question relates to when you are shimming to change the relative angle of the neck to the body . . . (ie not shimming to achieve change to the parrallel height of the neck in relation to the body . . if you get my drift ?)

ie . . for example if you wanted to raise the strings by say 1mm at the bridge compaired to their existing position, how thick would the shim need to be to achieve thie required change in neck angle ? . . . would you be talking about a shim made of a piece of newspaper ? . . or ordinary A4 office paper . . or thin cardboard . . or thicker cardboard ? . . .

I guess this could be worked out by trigonometry . . . . . but that wouldnt take into account how much the shim material might compress when the neck plate was done up ? . . . so I think only someone with a bit of experiance is going to have a feel for my question ? ?

Im about to put a Badass bridge on one of my fender instruments and will need to raise the string height between 1 and 2mm to acheive the fit. . . . I understand fully, and am confident with the process of Shimming . . . but I dont have the slightest clue how thick the shim material will need to be to achieve the relief of 1 to 2mm that I'm aiming for ?

And am hoping not to have to take the neck/body to bits umpteen times to get it right by trial and error !

any advice much appreciated ?

Thanks again for an excellent pinned thread.

Edited October 3, 2010 by Nostromo

[BOD2]

[quote name='Nostromo' post='975812' date='Oct 3 2010, 11:07 AM']ie . . for example if you wanted to raise the strings by say 1mm at the bridge compaired to their existing position, how thick would the shim need to be to achieve thie required change in neck angle ? . . . would you be talking about a shim made of a piece of newspaper ? . . or ordinary A4 office paper . . or thin cardboard . . or thicker cardboard ? . . .[/quote]

Remember that once the shim in is place you will still be able to adjust the action using the screws on the bridge pieces. The shim just gets the neck back into an area where the normal action adjustment will work.

Newspaper and standard A4 paper would be too thin to have any significant effect. You're probably looking at something the thickness of a stiff business card or some people use a piece of sandpaper, which would be around the same thickness.

Other than that I'm afraid it's just a bit of trial and error.

[Nostromo]

[quote name='andyjingram' post='919134' date='Aug 8 2010, 10:47 PM']Great little tutorial! I already knew the details, but as mentioned before, it has given me a bit more confidence to get on with it.

Does anyone know whether there is a simple mathematical way to work out the sort of shim thickness required to reduce/increase action by a given amount, or even roughly work it out? I have already tried a full neck pocket shim to effectively 'shallow' the neck pocket, but there is obviously more of a neck angle issue here. As I've already had the neck off a couple of times, I'd like to try to work out how much I need to add (after removing the flat shim) rather than just increasing by trial and error. I gather that it is really just a question of using either one or two thicknesses or card in most situations?

Cheers, Andy[/quote]


Hi Andy,

Im gona sit down and scientifically work out this shim thickness malarkey using some basic trigonometry soon as I get a bit of time to measure the neck pocket up and think it through ?

My calculation will be worked out using Fender Precision neck pocket dimensions and scale length etc . . . I'll post up the results as soon as I've had time to do it . . . .

Unless someone beats me to it that is ! ! !

Like I said earlier though, there's still the issue of compression of the shim you use when the neck screws are bolted back up . . for example, a card shim may appear to be "0.X" of a mm thick when you introduce it into the neck pocket . . but . . if it gets compressed when everything is tightened back up . . . then the actual amount of adjustment it produces will be a little different to that predicted by trigonometry ? . . I think ?

Cheers for now,

Edited October 3, 2010 by Nostromo

[Nostromo]

OK . . . any thoughts much appreciated . . . . . . .

Just measured up my PBass up . . . . the neck pocket is approximately 95mm long . . . . and the scale length, nut to bridge saddles, is approx 865mm long.

So by calculation we can deduce the following:-

Assuming the shim is a wedge triangle tappered from 1mm to Zero within the neck pocket, then, (by the maths of similar triangles) assuming also that we maintain the relative action height of the strings relative to the fretboard, then, that wedge shim, of 1mm thickness, will raise (or lower - depending which way round you introduce it) the strings 9.1mm from the saddles at the bridge.

This means that for every 1mm increase/decrease of clearance over the saddles that you wish to achieve at the bridge by the introduction of a shim, then, your shim wedge triangle taper needs to be approx 0.11mm thick at its fat end - privded that your neck pocket is about 95mm long to achieve that relative string height change of 1mm.

If your neck pocket is different to my PBass then the ratios change obviosly.

Funny thing about all this is though . . . . I still dont really have a clue what type/thickness of card shim material would be 0.1 or 0.2 or 0.3mm thick.

For my project, I need to raise my strings about 2 to 3mm over the bridge . . which means I need a shim wedge somewhere between about 0.22 and 0.33mm thick ? . . .

I woudn't have the slightest idea how thick a business card is and I've got no way of measuring one ! . . so I still dont exactly know what to use for my shim ! . . . ha . .

All that work and not really much further forward ! ! ! . .

[Knork]

I just did this according to BOD2's instruction on my Hodad bass and it simply worked perfectly. Great!

Edited January 30, 2011 by Krohurte

[alyctes]

Model-makers' styrene sheet? Available in various thicknesses; BITD I remember it in thicknesses from 5 thou up to 60 thou (about 1.5mm). 5-thou is thin enough to bend almost like paper.

And you could build up a laminate from pieces of 5 thou, if you wanted a wedge; use liquid styrene cement (from a bottle not a tube - apply with a brush) to fix the shimming pieces together.

(I have NOT tried this! In particular, liquid styrene cement might damage body finishes, if spilt. So, YMMV.)



[quote name='Nostromo' post='976339' date='Oct 3 2010, 07:46 PM']OK . . . any thoughts much appreciated . . . . . . .

Just measured up my PBass up . . . . the neck pocket is approximately 95mm long . . . . and the scale length, nut to bridge saddles, is approx 865mm long.

So by calculation we can deduce the following:-

Assuming the shim is a wedge triangle tappered from 1mm to Zero within the neck pocket, then, (by the maths of similar triangles) assuming also that we maintain the relative action height of the strings relative to the fretboard, then, that wedge shim, of 1mm thickness, will raise (or lower - depending which way round you introduce it) the strings 9.1mm from the saddles at the bridge.

This means that for every 1mm increase/decrease of clearance over the saddles that you wish to achieve at the bridge by the introduction of a shim, then, your shim wedge triangle taper needs to be approx 0.11mm thick at its fat end - privded that your neck pocket is about 95mm long to achieve that relative string height change of 1mm.

If your neck pocket is different to my PBass then the ratios change obviosly.

Funny thing about all this is though . . . . I still dont really have a clue what type/thickness of card shim material would be 0.1 or 0.2 or 0.3mm thick.

For my project, I need to raise my strings about 2 to 3mm over the bridge . . which means I need a shim wedge somewhere between about 0.22 and 0.33mm thick ? . . .

I woudn't have the slightest idea how thick a business card is and I've got no way of measuring one ! . . so I still dont exactly know what to use for my shim ! . . . ha . .

All that work and not really much further forward ! ! ! . .

[/quote]

Edited May 26, 2011 by alyctes

[mentalextra]

I just tried shimming the neck on my bitza jazz and it went well. The action is great but I now find that the 13th fret is buzzing which I assume to be raised. I have tweaked the truss rod and adjusted the action but still buzzing. Going to try and find a decent straight edge to lay across the frets and have a little look see.

[BriBass]

Hey Penguin, that photo tutorial was fantastic!. I spotted the thread and thought, ok, I'll have a gander...and it is great, but, it reminded me that when I got my '89 MIJ P Bass, I put a small piece of paper in that same place with my name and address on, in case it got stolen !...hmmm....it usually plays ok, but after not gigging for six years now (families hey) I have noticed that its buzzing a bit, probably have to have a set-up before next regular use. Once again, great thread. Thanks.

[BriBass]

Oops, sorry BOD2, I;m new ! I;ll get the hang of this someday ! (hopefully someday soon).And, I dont exactly know what a "sticky"is..? But the thread is definatley worth another. erm....thanks,

[Big_Stu]

Yeah, excellent "how to" all round. If anyone's planning on doing this, wood veneer is getting harder to find now, depending on where you are, with the demise of decent timber merchants. I've got a piece of oak veneer going spare which I can cut into strips. It has the advantage over card in that you can easily sand it into a wedge shape if you want to make a tapered shim.
PM me if you want a strip or two.

Though in the fairness of open markets, it should be pointed out there's a guy on Ebay who achieves a similar effect by angle-grinding his nuts down to the depth of the fingerboard

[popoctave]

Good write up, last time I did one I used a formica sample, worked well.

Edited November 4, 2012 by popoctave

[discreet]

Apologies for the zombie thread resurrection - but I needed to shim a J-neck and kept putting it off, thinking it was a huge job... did it just now following these instructions and using an old Bass Doc business card (thanks, Howard)!

What a huge difference! It takes five minutes and you don't even have to remove the strings. Excellent.

[karlfer]

Another zombie thread resurrection.
My red P sort of curves up at the dusty end. There is a little relief in the neck but don't ask for measurements, my eyes will tell you to bog off
If I shim it, I just can't get to grips with HOW this will make the fret board flat. Mr Red's fabulous diags don't have any with a fretboard that fractionally curves upwards at the high notes end.
It is not the only Fender I have seen this on, so any advice gratefully appreciated,
ta,
Karl.

Edited March 31, 2014 by karlfer

[Evil Undead]

[quote name='karlfer' timestamp='1396122326' post='2410232']
Another zombie thread resurrection.
My Nate Mendel sort of curves up at the dusty end. There is a little relief in the neck but don't ask for measurements, my eyes will tell you to bog off
If I shim it, I just can't get to grips with HOW this will make the fret board flat. Mr Red's fabulous diags don't have any with a fretboard that fractionally curves upwards at the high notes end.
It is not the only Fender I have seen this on, so any advice gratefully appreciated,
ta,
Karl.
[/quote]

Hey Karl!

My understanding is that it's pretty common on fender basses to have the frets a little higher from around 19 onwards or thereabouts, but I've never been sure whether it's the frets themselves or a curve in the board. I always wondered if there was a reason for this - maybe better access? Anyway...

Unfortunately a shim won't fix this. The only way to really get rid of it is to either de-fret, completely level the board and then refret and level the frets, which would be time consuming and pricey, or just have the frets levelled so that the height of those top ones is reduced - much cheaper but not viewed as a proper job by some crazy folk.

I know which I'd prefer though, if it really bothered me

[HowieBass]

Are you experiencing fret buzz at the dusty end but nowhere else on the neck? If so then I think you have too much relief. As for shimming, it obviously doesn't change the curvature of the neck (the relief) but it will change how that curve is 'presented' to the body (and strings). To my way of thinking, if you put a shim at the front of the neck pocket (a thin piece of card) then the headstock/nut will be slightly raised; put a shim at the back of the neck pocket and this lowers the headstock/nut with respect to the rest of the instrument - in both cases this will modify the action and you might need to adjust the relief and bridge saddles. A full neck pocket shim raises the whole neck and is a solution when the bridge saddles have bottomed out and the action is still too high for your needs.

[Evil Undead]

I may have misunderstood. I thought you were talking about the kinda uneven board ski slope thing up at the dusty end that so many fenders have - if it is that, then no amount of relief or lack of will fix it.

But yeah, it's worth giving the truss rod a try first just in case it is a relief issue.

[karlfer]

Thanks folks, limited access to computer, mother here on Royal visit .
No unwanted fret buzz. I set mine up like Sheehan. Pluck the string, let it vibrate and after a second or so, a tiny bit of buzz comes in.
String height brought to note "choking" points, then raised a tiny bit.
Neck relief, minimal, no more than 1/64th.
I think I'm being a bit of a tart here to be honest. The best Precision I have ever had, is the one I got from you Mel. As you know the action is lower than a snake's belly.
Yet even with that one, the fretboard is slightly inclined to the sky at the dusty end.
Bugger it, when me Ma goes I'm just gonna shim it. It's not that it's bad, far from it, I just like a very low action.
Bassists eh

Edited March 31, 2014 by karlfer

[HowieBass]

If the action is where you want it and there's no unwanted fret buzz then why worry about the slight curvature that you're seeing? You don't need to fix (shim) something that isn't broken...

[karlfer]

Because the curve up at the dusty end is preventing me getting the action lower between 5th/14th frets.

[HowieBass]

You did say "No unwanted fret buzz"... you mean you DO get fret buzz at the dusty end if you lower the action to where you want it. Well if the relief is already minimal as you say then I can see why you're talking about a shim LOL

[karlfer]

Sorry Mr. Bass, I'm not great at explaining myself.
OK, wanted fretbuzz, is when I pluck an open string, let it vibrate and eventually it will give off a little buzz on the open string.
There is no fretbuzz at the dusty end, but if I lower the action any more, the notes choke.
The action is a little bit higher than I like between about the 7th and 14th frets.
I'm going to shim it tomorrow night, after my mother has gone back home, and see what the result is..
Cheers,
Karl.