Tech Talk: How to build better parts guitars

Routing template variations and neck fit can be the achilles heel of a Jaguar or Jazzmaster-inspired build but fear not, help is at hand.

Building a guitar from parts is a fantastic way of learning how to maintain and repair stringed instruments. Depending on what style of instrument you’re making, you’re likely to encounter a host of common issues that we techs deal with on a daily basis.

You’ll touch on things like bridge placement for proper intonation, how to align the string path, soldering in pickups and, if you’ve chosen non-standard hardware, maybe routing. Even brand new necks may require some extra fretwork to play cleanly all the way up the neck. And after that’s done, you’ll need to finish the nut slots on that pre-cut nut you bought that was 100 per cent supposed to fit… but doesn’t.

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An older build. MJT Body, Warmoth neck, a trio of D’Urbano Firebird pickups, Mastery hardware

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While doing a partscaster or ’master of your own is as exciting as it is educational, it can also be frustrating. In the same way that you’ll learn the techniques of guitar repair, you’ll also come to understand the deflating feeling of running into a brick wall of a problem – the kind of unanticipated issue that stops you dead in your tracks.

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A recent MJT build. Mastery bridge, Antiquity pickups, Descendant Vibrato. Beautiful guitar!

In these moments it pays to take a walk away from the bench and have a good, long think. In this month’s column, let’s talk about a few of the issues I’ve run into on some recent parts builds.

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Building up a parts guitar? There are a few things worth considering as you go along. For one, the shape of the rout, which didn’t play nicely with the Descendant we installed

Cavity routs

It’s difficult from a visual, online-only examination to determine exactly what body template is being used by various parts manufacturers, and on guitars like Strats and Teles the differences between modern USA, vintage and import shapes are negligible.

Perhaps you’ll notice that the bridge needs to be moved backwards slightly or that the tip of the pickguard on the treble side cutaway doesn’t exactly fit. But when it comes to Jazzmasters and Jaguar style guitars – which I basically only work on these days – the template used can have a huge impact on how difficult the job will be as the build progresses.

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Using a Dremel to quickly sand away excess finish in the vibrato cavity of my sparkle Jaguar

The main issue that I’ve had to deal with is the shape and size of the vibrato cavity. The internals of most non-US-made vibratos are smaller than their American reissue counterparts and so, on most Japanese guitars, the shape of the body cavity meant to accept them isn’t as big. And those bodies happen to be a very common pattern for parts makers.

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Enlarging the rout of the MJT body to accept the Descendant vibrato destined for it.

So when you go to install an AVRI or vintage Fender unit, it either won’t fit, or it’ll bolt on just fine but when you go to string it up, you’ll find that the vibrato gets stuck as it rubs up against the walls of the rout. This is no good at all.

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Gently removing material from the neck pocket of a Jaguar body

When this happens, as with each of the partsmasters I’ve built recently, it pays to have a Dremel on hand. Using a simple sanding attachment, I quickly adjusted the size and shape of the rout, first removing as much finish as necessary and then sanding off a millimetre or two around the perimeter of the cavity. The good thing is, if it doesn’t look especially beautiful after you’re done, once the vibrato is installed you’ll never even see it.

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The MJT body with the proper guard (US shape)

If you’re using a Mastery or Descendant vibrato, those two are designed for a universal fit, but even with the Descendant, on my gorgeous Lilac-finished body I still had to remove material for it to work smoothly throughout its range. The rout on my sparkle Jaguar body was the right size and shape, but sparkle buildup around the top was problematic. Same procedure here.

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The MJT body with the wrong guard (Japanese shape)

Neck fit

Another potential problem that comes up when ordering parts from multiple vendors is one of neck fitment. Sometimes the neck pocket will be slightly undersized or oversized for the neck intended for it. Happily it’s usually a simple matter of sanding away just a sliver of material. Actually, when we’re dealing in extremely small differences, sanding off the leftover finish in the neck pocket almost always does the trick.

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Another example of a poor fit. MJT body, Japanese ’guard. We ended up acquiring a new US-spect ’guard instead

Even so, it often pays to order from the same manufacturer, or at the very least, get accurate measurements in an attempt to avoid this issue. Otherwise, some gentle sandpapering should help.

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A Thurston Moore ’guard on the same body to illustrate a far better fit

Template trouble

A third issue to watch out for is when you mix those body templates I mentioned earlier. Not only do the routs differ, but so do the overall shapes of USA and non-USA bodies. With Jazzmasters and Jaguars, the difference may not be discernible until you install the pickguard.

Take a look at the example here. First, we have the provided pickguard on the Lilac body, both in the basic American Reissue shape. Notice how the treble side of the guard follows the shape of the body, how the lines flow together from neck to toggle to output jack.

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A Decoboom ’guard on the same body, also to illustrate a better fit

In the next picture, I’ve placed an Allparts pickguard, stated to be for a ’62 Reissue, yet it has the telltale hallmarks of the MIJ/CIJ shape. Follow the same path from before: neck to toggle, where the fit veers off suddenly, then down to the output jack where the more bulbous lead circuit control area takes up more space, interrupting the lines of the body.

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Lilac on the bench, largely completed and ready for strings

I call attention to this because it’s one of the easiest ways to spot a parts build from across the sales floor. Even some well known builders seem to forget the importance of this aesthetic touch, and that really puts me off when I’m shopping for a new guitar.

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My test fit of the Sparkle Jag revealed a fit problem with the way the lower control plate sits on the body

This rule also applies to Jaguars, but there’s another catch with those guitars: the chrome control plates almost never line up without some extra work. The Jazzmaster’s shorter, younger sibling has three extra control plates that you’ll have to consider once you’ve lined up the main plastic pickguard using the neck and bridge inserts. Let’s look at my very cool Coke Bottle Sparkle Jaguar body that I finished up just this week.

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Using a belt sander I removed material from one side, then re-shaped to fit the guard

Upon my initial test-fit, I found that the lead volume and tone plate looked totally wrong, with the jack area jutting out into the negative space of the sparkle finish. Now, to be fair, even vintage Fender production varied quite a bit and, if you ask me, some examples of totally original custom-colour instruments show some rather sloppy installation.

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Much better!

But ‘vintage-correct sloppiness’ was not going to cut it for me, a picky and precise individual. If I’d left it like that, it’s all I’d ever see. So, what’s a guy to do? Well, this picky boy used some careful alignment tricks to figure out how to get that plate in line.

First, I slid the control plate partially under the pickguard and moved it around until I was reasonably happy with the fit. Next, I marked where the guard overlapped on the metal plate with masking tape for reference, then fired up my belt sander, which I used to gently remove material from that side of the plate.

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My new Sparkle Jag and my ’63/’65 Jaguar loaded with Novak XII pickups

I went back and forth a few times, working slowly to ensure I was on the right track. And with a little effort, I soon had a control plate that lined up with the lines of the body in a way that made me extremely pleased. From there, I finished the build and fell in love with my sparkly new friend. I hope you have a similar level of success with your builds!

Follow Mike on Instagram @puisheen.

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