Shimming the Jaguar neck pocket.

With the neck on the Jaguar and the electrics complete – all I need is a new set of strings. I adjust the Staytrem bridge so it’s almost flat to the pickguard, careful however to leave a little space so the bridge can just rock slightly, side to side. This is essential for the correct operation of the tremolo. The lock on the tremolo plate is set, so that the spring on the plate is countered. This effectively locks the plate in place while the strings are brought up to tension. When tuning the strings, you actually adjust each string’s tension individually – the sum tension at full tuning being the force that the tremolo spring is designed to work and balance against. If the lock isn’t engaged when the strings are tightened, then the effect of an increase in tension on just one string is transmitted across all six. This has the unfortunate effect of constantly retuning the guitar all the time you adjust it – making cross reference methods of achieving correct intonation and tuning, extremely difficult. It’s one of the most frustrating things about tremolos. To do the job properly, you need to be able to temporarily lock off the tremolo in the correct, balanced position.

The lock idea was originally brought in by Fender, on the Jaguar and the Jazzmaster models, and was an improvement over the floating tremolo design of the Stratocaster. It was specifically designed to stop the guitar going out of tune if a player should happen to break a string. Without the lock – the reduction of string tension as a result of the breakage would tend to knock the rest of the strings out of tune, as the tremolo spring pulled slightly more than the combined force of the remaining strings. The lock acts a simple shelf latch, against the pull of the tremolo spring. It’s adjusted to the balance point so that when it’s engaged, and a string is broken, then the tremolo plate is physically held in place, and stopped from releasing tension on the other strings. For that reason, it’s also really useful to engage the switch, with the plate in the correct balance position, when restringing.

I’m stringing up using a set of Custom Light .10’s. A regular light set, but with a heavy .52 bottom end for a bit of extra spank. The Jaguar has a lower neck shear force due to the shorter scale, and therefore the string tension is noticeably a little slinkier than on a guitar of standard scale length. Heavier strings exert a greater string tension – so the extra overhead gained from the shorter scale means you can get the benefits of the heavier strings without, necessarily, having to work extra hard with your fingers. The Staytrem bridge saddles are already set to follow the 7.5″ radius of the fingerboard – so apart from the bridge height adjustment, there’s no individual string height adjustment to be done. This is a first time stringing – so I’m not expecting a fully adjusted action – but, disappointingly, it has to be said – with the full set of strings fitted, stretched and tensioned, and the bridge down to the deck – the action isn’t exactly what you’d call ideal.

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In fact, the action is super high. The pickups also appear to sit quite high compared to the fingerboard – so much so that, for a while, I reckon it must be the neck or the neck pocket cutout that isn’t dimensioned properly. A quick check with the ruler however, shows the problem must instead lie either with the bridge, or the nut. The nut is still stock and not yet fully slotted, but the few millmetres difference here won’t be reflected anywhere near as much at the higher frets. It seems that the Staytrem bridge must be significantly higher than the stock specification – resulting in the raised action. Or something else is screwy…

Certainly – one of the advantages with the improved Staytrem design was a more reliable seat for the strings as they pass over the saddles. In the original design, strings could easily jump or slip from the saddles during play, or when operating the tremolo. The improved design, based on the later Mustang bridge, appears to use bigger saddles with deeper, more defined slots cut for each string. Taller saddles also, presumably, increase the string break angle – resulting in tonal and stability benefits. It looks like the bridge here, is a touch too high for the geometry of the guitar.

A bit of research however provides another possible solution. In the original specification and component load out – there’s actually a shim inserted in the neck pocket. You can even find original parts for resale on eBay. I can’t find out the actual working dimensions – but that’s not a problem. I have a look at the Stew mac website, to find pre-shaped shims available for Fender neck pockets. Now they’re expensive for what they are – but shaping a thin piece of maple accurately to provide a consistent wedge shape is tricky. It can be done starting with a piece of maple veneer – but it’s time consuming and difficult to do accurately, by hand. Since it’s vital to keep good wood-to-wood contact between the neck and body, a properly shaped wedge is important. Not only to fit the whole of the pocket accurately, but also to provide a consistent angle change across the neck. I also don’t know the maths to work out what kind of adjustment I need to make. I’m going to need a bit of a try-it-and-see approach. StewMac’s pre-formed shims are ideal.

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The shims come in three degrees of tilt. 0.25, 0.5 and 1 degree. StewMac advice says 0.5 is the most useful, “but there are times you’ll need others”. They can be stacked to offer in-between degrees of tilt. Conveniently, they offer a set of three for a slight discount. Since these will have to come from the US, I order one set of three, and then two spare 0.5 degree shims, just in case I ever need to consider shimming another project.

Once they arrive, it’s just a matter of slipping the neck out of the pocket, (again), and inserting a shim to test fit. I go with Stew Mac’s suggestion, and try one of the 0.5 degrees wedges. There’s a bit of a trim needed, and the pre-drilled holes don’t quite match my screw holes. It’s easy work with a scalpel for the retrim, and I use a paper hole punch to punch out extentions to the screw holes so that the screws don’t split the thin sheet of maple.

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Then it’s a simple job to re-attach the neck and neck plate, and to bring the guitar back up to tune. I don’t need a ruler to notice a marked difference.

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The whole geometry and relation of neck to body seems to have changed, and the action is much closer to what I’d expect, to begin a decent setup. But the bridge is still decked. I try again, but this time use a 1.0 degree shim. It’s the same procedure, the same trim to fit and the same hole punch trick on the holes – except this time the wedge is too thick for the hole punch. I have to saw at it carefully with a rat-tail file to extend the pre-drilled holes to suit. As the neck goes back on, things look much more promising. Once the screws are tight, I bring the strings up to tension and then do the old trick of backing each neck screw off about a quarter of a turn. The familiar clunk and creak means the strings have literally pulled the neck into position – with the best wood-to-wood contact possible. Tightening the screws up again, means that contact is held and maintained, transmitting the maximum vibration along the whole length of the guitar.

The result is pretty much what I’m looking for. The guitar still feels resonant when played acoustically. It looks like there’s been no real effect on the wood-to-wood contact, and that the shim must therefore be properly shaped and consistenmt over the width of the neck pocket. The strings now appear to run parallel with the neck – virtually touching every fret – with a slight bow due to string tension lifting the strings away from the fingerboard towards the nut. Naturally – there’s still a whole load of set up and adjustment, on the bridge, yet to do. The strings now also touch the pickups – so I first sink them into the body a little more, using the pickup adjustment screws. (I’ll make final adjustments once the guitar is set up properly). Then I adjust the bridge height by turning both of the hex screws located – one each – at the treble and bass ends, until the strings sit within a comfortable range, with which to make final set-up adjustments. Yet – even without those fine adjustments, the guitar feels good to play already. Promising stuff. Say what you like, sometimes you just have to resort to a shim.

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