Neck shim material?

[philw]

All,

My new Surf Jag (http://basschat.co.uk/topic/287400-nbd-jagtele-mashup/) needs its neck shimmed up a little - a millimetre or so. In the past I've used pieces of card for this kind of thing, but what's the preferred material among the proper luthiers out there?

Ta
Phil

[HowieBass]

I think wood veneer gets used as it won't compress the same way cardboard could. I've used thin plastic sheet (cut to size with ordinary kitchen scissors and with holes drilled for the neck screws when I needed to shim the full neck pocket).

[Manton Customs]

I like veneer if a shim is necessary as it's still a wood to wood contact and it will not compress too much. Just a little at the rear of the pocket should give you the necessary neck angle.

obviously I'm not talking about on my builds, or something would be seriously wrong if I was resorting to neck shimming!

Edit: Howie beat me to it!

Edited June 27, 2016 by Manton Customs

[PlungerModerno]

Anything that works, works.

Card will compress - unless you compress it before inserting it as a shim. I'd imagine wood, metal, paper, cloth, plastic etc. could all work...
Cloth would probably need some resin to make it stiff enough for thicknessing & shaping (I'm a believer in tapering the shim to fit the angle of the pocket as much as is reasonably possible).

EDIT: Nothing wrong with a shim! You should be able to get a bolt on necked bass with low frets, a slim neck (front to back), and low string height and have the grub screws not stick out a bunch and tear the hand when muting. The same bass should be able to run higher action, [u]and[/u] either a thicker neck or taller frets (e.g. going from a fretless neck to a fretted neck with jumbo frets) - the only way to do this without using different length screws or having them scraping hands is to use a shim (use long grub screws but use a shim with the first setup (w/ thinner neck) to have a positive neck angle that will keep the grub screws close to or below the surface of the saddles). This is based on BBOT or other similar styles of saddles. IMO of course!

Edited June 27, 2016 by PlungerModerno

[philw]

Thanks all.

Phil

[Manton Customs]

[quote name='PlungerModerno' timestamp='1467054257' post='3080872']
EDIT: Nothing wrong with a shim! You should be able to get a bolt on necked bass with low frets, a slim neck (front to back), and low string height and have the grub screws not stick out a bunch and tear the hand when muting. The same bass should be able to run higher action, [u]and[/u] either a thicker neck or taller frets (e.g. going from a fretless neck to a fretted neck with jumbo frets) - the only way to do this without using different length screws or having them scraping hands is to use a shim (use long grub screws but use a shim with the first setup (w/ thinner neck) to have a positive neck angle that will keep the grub screws close to or below the surface of the saddles). This is based on BBOT or other similar styles of saddles. IMO of course!
[/quote]

There's nothing wrong with a shim if it's necessary to get an instrument playable (or on a parts bass), but if one is required on a new bass built from scratch then there has been an obvious miscalculation and the neck angle/relation between neck and bridge has not been set correctly. Neck shims are an after thought to fix poorly executed planning, a fix, or as in this case the assembling various parts.

The scenario you're describing is not a particularly common one (switching back and forth between necks). However if the neck angle was correct in the first place and the necks are chosen sensibly, then there would be no issue switching between them without a shim, as all you would be talking about is the height of the frets.

The correct neck angle/shimmed neck should result in a straight edge laying a long all frets and resting on the bridge at it's lowest position.

Edited June 27, 2016 by Manton Customs

[PlungerModerno]

[quote name='Manton Customs' timestamp='1467061542' post='3080954']
...The correct neck angle/shimmed neck should result in a straight edge laying a long all frets and resting on the bridge at it's lowest position.
[/quote]

You're spot on - for maximum adjustability (what you want in 99% of cases - where the hardware & the body neck etc. are a good match). For maxiumum playability, especially on a Bitsa - you may need to throw away some of the adjustability to keep the spiky grub screws down a little, using a thicker shim than strictly nescessary to make the bridge usable. more of an aside than anything.

[quote name='Manton Customs' timestamp='1467061542' post='3080954']
There's nothing wrong with a shim if it's necessary to get an instrument playable (or on a parts bass), but if one is required on a new bass built from scratch then there has been an obvious miscalculation and the neck angle/relation between neck and bridge has not been set correctly. Neck shims are an after thought to fix poorly executed planning, a fix, or as in this case the assembling various parts.

The scenario you're describing is not a particularly common one (switching back and forth between necks). However if the neck angle was correct in the first place and the necks are chosen sensibly, then there would be no issue switching between them without a shim, as all you would be talking about is the height of the frets.
...
[/quote]
+1

[luckydog]

[quote name='philw' timestamp='1467052817' post='3080847']
All,

My new Surf Jag ([url="http://basschat.co.uk/topic/287400-nbd-jagtele-mashup/"]http://basschat.co.u...jagtele-mashup/[/url]) needs its neck shimmed up a little - a millimetre or so. In the past I've used pieces of card for this kind of thing, but what's the preferred material among the proper luthiers out there?

Ta
Phil
[/quote]

I'm not a luthier, but I once made a shim for that sort of thickness from a thin single piece of solid mahogany, planed and sanded. Or I suppose one could laminate hardwood veneer sheets by gluing with PVA and pressing them together ?

LD

[Twincam]

There could be an argument a small piece of card will actual make a better contact as it will compress into all the little tooling marks and natural grain. Once compressed it would be very hard too.
I'm not debating this btw I'm just looking at it from a different angle lol.

However a small section is unlikely to make no difference at all no matter what its made of (rubber may be a bad choice) as long as the shim is of reasonable thickness and it doesn't need to be so thick its lifting a significant portion of the neck up from the body.

[largo]

Bit of card with your name on it. Bass gets nicked, easy to identify. Simplez 😀

[darkandrew]

I know it's already been discussed, in a previous thread,that a partial shim across the last screws can lead to the neck bowing due to the part of the neck that's above the void in front of the shim being pulled into it and creating a ski jump at the end of the neck. I've been thinking about this - is this actually likely as it's not just the neck that would have to bow but also the truss rod that's going through it?

I ask this because I've just taken ownership of an Ernie Ball Sterling bass whose E string saddle is as low as it can go but needs to go a bit lower, and so I was thinking about putting a shim in the neck pocket and was wondering whether to use the Ernie Ball partial shim or make my own full pocket shim out of maple veneer.

Edited August 26, 2016 by darkandrew

[HowieBass]

@darkandrew - if everything else about the current setup works for you then I'd be inclined to go for a full neck pocket shim.

[darkandrew]

[quote name='HowieBass' timestamp='1472232086' post='3119716']
@darkandrew - if everything else about the current setup works for you then I'd be inclined to go for a full neck pocket shim.


[/quote]

With the truss rod set so that the neck is flat, the straight line across the frets just skims across the top of the pickup and meets the bridge halfway up the saddle when put at its lowest position. To align this with the top of the saddle using a straight, full pocket shim would take a shim of about 2mm thickness, whereas as tapered or partial shim would only need about 0.5mm to acheive enough leverage to reach the top of saddle. So it's quite tempting to shim just one end but, like I said I've been put off by the scare stories of ski-jump necks.

Edited August 26, 2016 by darkandrew

[HowieBass]

I had a similar problem with my Cort Curbow 5 (bought secondhand via eBay) where both the G and the low B were causing problems because I couldn't get them low enough. The saddles are of a cast design, which could have been filed for a deeper groove, but for me it was easier to raise the whole neck with a shim.

[darkandrew]

[quote name='HowieBass' timestamp='1472235909' post='3119754']
I had a similar problem with my Cort Curbow 5 (bought secondhand via eBay) where both the G and the low B were causing problems because I couldn't get them low enough. The saddles are of a cast design, which could have been filed for a deeper groove, but for me it was easier to raise the whole neck with a shim.
[/quote]

Did you use a full pocket shim or just shim one end?

[HowieBass]

Full pocket; I used some thin plastic sheet that I had handy, thin enough to cut to shape with scissors. I drilled holes to accommodate the neck screws. I reckon the plastic is hard enough not to compress much but has sufficient flexibility to provide good contact between the neck and the pocket.

EDIT: I actually cut three identical pieces and ended up using two thicknesses in the pocket.

Edited August 26, 2016 by HowieBass

[Manton Customs]

I prefer a shim (when one is absolutely necessary) to be at one end to gain maximum effectiveness from minimum material. It's also completely invisible whereas a full pocket shim may be seen. To clarify, I don't mean really small but from the heel end to the first mounting screws and shaped to fit the corners of the pocket.

There are no real concerns about a shim causing a ski jump, these typically develop a little lower down the neck. The heel itself is too shorter distance, too supported and also too thick (typically around 1") for bowing to be a real concern.

[HowieBass]

@Manton Customs - if the neck angle is correct without any shims wouldn't a partial shim at either the front or back of the neck pocket introduce a tilt in the neck?

[Manton Customs]

[quote name='HowieBass' timestamp='1472285978' post='3120011']
@Manton Customs - if the neck angle is correct without any shims wouldn't a partial shim at either the front or back of the neck pocket introduce a tilt in the neck?
[/quote]

I'm not sure I understand the question....if the neck angle was correct why would you add a shim?

If any of the saddles are bottoming out before the strings rest on the frets (or are very close to doing so), then the neck angle is not correct for the bass in its current state. Over time the neck pocket itself can shift due to the constant pull of the strings and changes within the wood. So the purpose of the shim is to give the bass back the required angle. The thickness of the typical shim required is pretty inconsequential as far as the playing/feel of the bass goes.

[HowieBass]

[quote name='Manton Customs' timestamp='1472300442' post='3120154']
I'm not sure I understand the question....if the neck angle was correct why would you add a shim?

If any of the saddles are bottoming out before the strings rest on the frets (or are very close to doing so), then the neck angle is not correct for the bass in its current state. Over time the neck pocket itself can shift due to the constant pull of the strings and changes within the wood. So the purpose of the shim is to give the bass back the required angle. The thickness of the typical shim required is pretty inconsequential as far as the playing/feel of the bass goes.
[/quote]

Wouldn't you need a full neck pocket shim if the neck angle is correct but the saddles are bottoming out? This won't happen with a hand-built bass but if quality control isn't all it could be in a factory it could happen with a production line instrument (I know you've already stated this). The instrument I had to put the full pocket shim in has a Luthite body which has a rather unusual profile (Luthite is a moulded composite material, see https://en.wikipedia.org/wiki/Luthite for info) - the bridge is set at an unusual angle in a pre-formed receptacle. It would be difficult to machine the body to lower the bridge. The neck is wood with an Ebonol fingerboard and no doubt the ideal solution would be to get a replacement neck that has a thicker heel. My solution, which cost me nothing, was to add the thin plastic shim.

[Norris]

The whole point of the neck angle is to get the frets on the bridge end of the neck to the correct height based on the straight line between nut and bridge I.e. your strings. Regardless of the factory neck angle, what Manton is saying is that you now need slightly more neck angle to get the geometry correct for your bass in its present state. A slight shim at the heel end will allow you to get the action you're after without the saddles bottoming out

[HowieBass]

@Norris - I'll try this with my Curbow 5 but it seemed to me that all the neck heel, in contact with all of the full pocket shim, in contact with all of the neck pocket would be the better engineering solution. I know that when people add high mass bridges with a chunky baseplate to an instrument, they often run out of travel with the saddles and the usual solution is rout the body to drop the whole bridge down by a millimetre or so... are you saying that another option is add a shim to the back of the neck pocket to tilt the whole neck backwards? From an engineering/geometry perspective there doesn't seem much difference between dropping the bridge into a shallow rout or raising the whole neck with a full shim

[Manton Customs]

[quote name='HowieBass' timestamp='1472302657' post='3120180']


Wouldn't you need a full neck pocket shim if the neck angle is correct but the saddles are bottoming out? This won't happen with a hand-built bass but if quality control isn't all it could be in a factory it could happen with a production line instrument (I know you've already stated this). The instrument I had to put the full pocket shim in has a Luthite body which has a rather unusual profile (Luthite is a moulded composite material, see https://en.wikipedia.org/wiki/Luthite for info) - the bridge is set at an unusual angle in a pre-formed receptacle. It would be difficult to machine the body to lower the bridge. The neck is wood with an Ebonol fingerboard and no doubt the ideal solution would be to get a replacement neck that has a thicker heel. My solution, which cost me nothing, was to add the thin plastic shim.
[/quote]

Well I wouldn't call the neck angle correct if the saddles are bottoming out personally . Anyway, no you wouldn't necessarily need to shim the whole pocket, but there's nothing wrong with that approach (whole shim). There are quite a few different fixes for the issue and the simplest and my preferred quick fix would be to shim the heel end. This would tilt the neck back an imperceptible amount.

I'm familiar with the curbow and they are built to a decent standard, however I've seen a lot of problems with the Luthite bodies, such as the pocket warping (even though it's not wood!). Which sounds like what's happened to you.

Just so I'm clear- I was in no way criticising you for using a full pocket shim, just saying I prefer the alternative .

[Norris]

Yes, recessing the bridge is another, albeit more intrusive method of achieving the same result. A heel shim is the quickest fix. A full shim (thickness depends whether you angle it) involves a bit more work but will be visible. I doubt whether you would hear the difference between a partial shim and a "full contact" one tbh

[EBS_freak]

I can't believe this conversation is happening...

Use pretty much anything as a shim, credit card, vaneer, whatever... it makes zero difference to tone or anything like that - that's all a myth. If the screws are tight enough, the job is done.

And a shim is a common practice utilised by many luthiers, including those that are considered "world class",I would certainly argue that it is not a failing in it's manufacture.