Tonerider bridge pick up, scale length and cavity routing

Hi all

I'm certain that this has been posted (many times) before and sorry for my lack of searching abilities.

I'm doing a mock-up build and have installed the Tonerider bridge pickup. However, when seated in the cavity, it causes the bridge to be approximately 2-3 mm further back.

I'm ok with re-drilling the bridge screws but my scale length is going to be significantly affected - ie even if the saddles were fully forward, I'm still not sure that I'd make the required length.

Is it standard to be routing out the cavity for these Toneriders? If so, recommendations for techniques/tools for doing so?

Thanks in advance

Hi Johnny, what's the kit you're building? TL? are there pre-drilled holes for the bridge? Generally you can be a couple mm longer and be OK.

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Thanks for the reply.

DTL-1 and yes the holes were pre-drilled.

I measured from nut to 12th fret and got the 32.4cm. Measuring 12th fret to the saddles was just under 33cm (so I need at least 5mm of play in the saddles, which I just don't think I have).

I've packed everything away for the day but I'll take a couple of photos and post tomorrow.

Thanks again for your help.

I have the same kit and started on it a few days ago.
Yes, I trimmed some of the pick up route out with my Dremel.
I fitted the neck so it was inline with the neck pocket after I rounded the corners of the back of the neck so it fitted back further. Mine measured 323.5mm to the 12 fret.
I’m fitting a wilkinson bridge to my kit. If you are using the stock bridge you should have a stack of adjustment.
Another thing with mine is I had to move the bridge over to the control side about 4mm so the strings will line up with the neck with out moving the neck over leaving a gap in the neck pocket. One more thing with mine was it needed a 3mm shim in the neck pocket so I could get some adjustment for the saddles.
Bit of work to get it right as you can see.. ;)

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Is it standard to be routing out the cavity for these Toneriders? If so, recommendations for techniques/tools for doing so?

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It's not the Toneriders, it the factory routing and drilling that's out. Unfortunately this has been a common issue with the many of the TL kits for a long time, and it's frustrating that it's still on-going. If you do need to adjust the pickup cavity, it can be done with a rotary tool (eg: Dremel) and a sanding drum if you don't have a router.
If you need to relocate the bridge holes and don't have an adequate drill press, there are drill guides you can buy or a number of DIY options on YT & elsewhere.
Not sure if your body is also predrilled for a string-through bridge. If so there's help available here for that as well.

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I measured from nut to 12th fret and got the 32.4cm. Measuring 12th fret to the saddles was just under 33cm (so I need at least 5mm of play in the saddles, which I just don't think I have).

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When setting out your bridge location, you want to measure the entire scale length from nut to saddles, not 1/2 from the 12th fret.

Secondly, the saddle you want to measure to is the E1 (treble) saddle, and you want to position that saddle so there is 1-2mm of thread from the intonation screw visible through the opening in the saddle where the string passes through. (this is for block saddles as shown with your kit).
Now measure the full 648mm from the fretboard-side of the nut to the "break point" of the saddle (where the string will leave the saddle and be free of contact). This determines the required position of the bridge for all the strings to intonate properly.
The treble E saddle will always be the furthest forward (closest to neck) and the bass E saddle will typically be the furthest away from the neck (nut), though there are exceptions with the G string, but that's another subject.

Sometimes the saddles really need to be set as far forward as they can to get the intonation correct with these kits. As long as the barrel is still firmly on the adjustment screw, then the screw can be flush with the front of the saddle barrel, or even with it slightly inside the barrel if necessary. If necessary, you can fit longer adjustment screws (on the kits they are a standard metric size, but I can't remember if they are M2 or M2.5 threads).

Note that the scale length is 25.5", which is 647.7mm. That 0.3mm (compared to 648mm) may not sound like a lot, but it could be important.

The intonated length will be a bit longer than the scale length. For each string the intonated length will be longer than the scale length by an amount dictated by two factors:

1) The 'end effect' of the string having to transition from being fixed to being fully vibrating at either end. This makes the string effectively slightly shorter, and so produces a slightly higher tone than expected. For the full string length, you simply change the tension to tune to pitch, but when fretting at the 12th fret to set the intonation, you still have the full 'end effect' working. This 'end effect' length at either end end of the string can be taken as equal to the string diameter, so the effective vibrating string length is two string diameters shorter than the measured string length.

For a 648mm scale, and a 1mm diameter string, the effective vibrating string length is 646mm. So when you fret at the 12th fret to set the intonation, the actual string length is 324mm but the effective vibrating string length is 322mm. But to be an octave above the open string note, the effective vibrating string length needs to be half that of the effective open string length and so be 323mm. So the saddle then needs to be moved back by 1mm to make the effective string length 323mm.

The general result is that you end up moving the saddle back by a string diameter for this factor in the intonation requirement. So about 0.25mm for a top E string and 1.2mm for a bottom E for this part of the extra intonation length required.

2) The other and generally greater part of the extra intonation length is down to the increased tension in the string caused by pressing it down to the fret, both increasing the tension and slightly (temporarily) stretching the string. The greater the string height/action over the 12th fret, the greater the increase in string tension and the higher the frequency the note will sound at. So the saddle needs to be set back further to make the string longer and lower its frequency for the increased string tension. And you generally have the treble strings set at a lower height than the bass strings, which is another reason the bass saddles normally end up further back than the treble saddles.

Different string materials also have different values of Young's modulus, so wound strings will behave slightly differently to solid strings. And the tension difference changes for different string gauges as well even though the string length change may be identical.

So whilst you can calculate the approximate extra length you'd need to move the saddle for this effect, there are lots of other factors to take into account, like how hard you press down with your fingers when fretting and the length of string beyond the nut and bridge. So it's far better to simply use a tuner and set the saddle positions empirically rather than try and calculate a position (which is always going to differ from player to player as everyone will fret a string with more or less force).

The only time you may want to calculate saddle position is if you are building your own acoustic guitar and want to know where to put the bridge, and adjust any soundboard bracing accordingly.

So those two factors, end effect and change in string tension by fretting, are the reason why the saddle positions end up further away from the nut than the notional scale length and the bass strings more than the treble strings.

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Originally Posted by McCreed

It's not the Toneriders, it the factory routing and drilling that's out. Unfortunately this has been a common issue with the many of the TL kits for a long time, and it's frustrating that it's still on-going. If you do need to adjust the pickup cavity, it can be done with a rotary tool (eg: Dremel) and a sanding drum if you don't have a router.
If you need to relocate the bridge holes and don't have an adequate drill press, there are drill guides you can buy or a number of DIY options on YT & elsewhere.
Not sure if your body is also predrilled for a string-through bridge. If so there's help available here for that as well.



When setting out your bridge location, you want to measure the entire scale length from nut to saddles, not 1/2 from the 12th fret.

Secondly, the saddle you want to measure to is the E1 (treble) saddle, and you want to position that saddle so there is 1-2mm of thread from the intonation screw visible through the opening in the saddle where the string passes through. (this is for block saddles as shown with your kit).
Now measure the full 648mm from the fretboard-side of the nut to the "break point" of the saddle (where the string will leave the saddle and be free of contact). This determines the required position of the bridge for all the strings to intonate properly.
The treble E saddle will always be the furthest forward (closest to neck) and the bass E saddle will typically be the furthest away from the neck (nut), though there are exceptions with the G string, but that's another subject.

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Yowsers - thanks for the detailed explanation. Feeling silly now for having only bought a 600mm straight rule. Hopefully my tape measure will still do the trick. Really appreciative.

Thank you, Simon for the very detailed explanation - the information is coming thick and fast and I'm doing my best to absorb it all. You can dive as deep into this stuff as you want, eh?

Really grateful for everyone's input and thoughts so far.

Kind regards

Attachment 42253

Measurement of top E from inside of nut.

This is using the re-drilled holes for the bridge but if I use those it's clear that some routing of the cavity is required in order to fit the pickup.

Am I on the right track by sticking with the pre-drilled holes and dealing with the pick up problem by some minor (ie about a mm or two) routing?

Thanks in anticipation

That looks good to me as you have enough thread left on the intonation screw to get the saddle within the margin. FWIW, the treble E strings on my guitars can intonate between 647-651mm. Some are bang-on 648. There aren't always hard and fast numbers with these things. As Simon detailed above, there are lots of variables.

Now, one thing I will say re: using a tape measure vs a steel rule is that the metal cleat on the starting end of a tape measure can have some play in it and vary the measurement depending on whether you're pulling or pushing the tape.

If you do not have a long enough steel rule yet (or can't get one) you can "calibrate" the tape measure by checking it against your 600mm rule. By determining the variable between the pull/push measurements, you can account for it in your scale length measurement. I know that all sounds a bit dodgy, and ultimately a 100cm rule is a better option, but sometimes we have to improvise.

I have a Stanley tape measure that is spot-on in both directions, so sometimes it's not an issue, but I still use a steel rule for critical set-out measurements.

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Am I on the right track by sticking with the pre-drilled holes and dealing with the pick up problem by some minor (ie about a mm or two) routing?

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That should be fine, but check that there is enough length in the bridge plate that it will cover the extended routing. You can position the bridge using the pre-drilled holes and scribe a line with a fine pencil at the neck end of the bridge. The line will show you how much wiggle room you've got from the edge of the pickup cavity.

I re-measured, starting at 100mm and still got the same measurement. Whew.

So, here's my dilemma (apologies for the pedantry but this feels like a "cross roads" moment that I'm going to royally stuff up!).

Attachment 42255Attachment 42256

The left picture is with the bridge in position (using the pre-drilled holes) which gives me my scale length. The second picture shows what I think I will need to route out.

I'm just triple checking but I think I just need to use the existing pre-drilled holes for the bridge and just route out the mm or so (I think this is the way I am heading and means that the front of the bridge lines up much better with the scratch plate). I'm going to use a sanding drum and take it very slowly.

The other option (ie making sure that the pickup is happy first and then fit the bridge relative to that) worries me because I'll have to set the bridge another 1-2mm back and I don't think I'll have enough play in the saddles (ie need longer threads) and have to fill and re-drill the bridge screw holes.

I'm pretty sure that I've answered my own question now but a "You got this, Johnny. I agree with the first option" would be appreciated :rolleyes:

Please forgive me - I hope to be a little more adventurous/less needy as I go along.

Option 1: Sanding drum away!

I had to do a similar sand on my TLA-1 kit.

I will just add one more thing to check before committing to either option. (sorry, meant to mention this before)

Check that the mounting holes for the bridge are indeed perpendicular to the fretboard/neck. There have been kits that were drilled slightly askew and this can cause more headaches.

If they are all good, I would go Option 1. At least you know there's plenty of bridge plate to cover that extended cavity now.

As for Option 2, longer screws are easily sourced and have been used to get others' bridge position problems fixed.


I'll offer a little tip for using the sanding drum, you can take it or leave it...

To keep a cleaner, straighter line along the top of the cavity, clamp a piece scrap timber (with a clean edge) along the pencil line and use it as a "bumper" (almost like a template) to keep the drum from jumping or digging too deep.
You still need to be careful because it's not like having a bearing on a router bit, but it helps!

Do one straight section then reposition the "guide" for next one. The little rounded corners can be touched up freehand or getting creative with the guide.
At the end of the day it's going to be covered up, so if it looks like a dogs breakfast, only you'll know! I just think we all at least try to be as neat as we can :o.

I wouldn't worry about intonation...distortion fixes *everything*!

The end hook on a retractable tape measure is loose so that it should read correctly when
a) hooked over the end of a piece of wood and pulled tight
b) pushed up against an object when measuring from that object e.g. a wall

What you don’t want to do is just place it so the end hook is somewhere between the two positions.

Like McCreed, I use a rigid metal rule for neck measurements. I have both 600mm and 1m rules as both come in handy. The 600mm one is good for placing on the neck to see where the line of the neck hits the bridge. A 1m rule is too long for this (unless the nut has been removed.

Another thumbs up for using a Dremel drum sander and a bit of wood as a guide/stop bar.

You may then need to enlarge the cable exit hole downwards a bit within the cavity, as you can sometimes end up with the pickup lead interfering with the pickup baseplate. Just enough so that the cable can bend downwards and run under the baseplate. If it doesn't, fine, If it does, don't try and put up with it, just make the bottom of the hole larger to a depth of 3-4mm.

After you get the intonation right. Double check the string alignment by putting in the 2 E string tuning heads and running a couple of strings to the bridge. As I said, mine was out around 4mm. While you are doing that check to see if you have plenty of saddle adjustment too. My saddles were sitting on the bridge and the strings were still to high of the fretboard.

Thank you everyone - your advice and willingness to help is humbling.

Very grateful.

Agree about the tape measure end.

Agree about making sure that the screw holes for the bridge are perpendicular. I'm going to make sure that the bridge doesn't move because of the screws going in at funny angles.

And, hell yeah, distortion fixes everything. Clean tone is for suckers who want to sound musical. Rock on!

Wow, this thread is now laden with good info on scale lengths and bridge placement etc.

Just on the Tonerider vs kit bridge pickup: I had to rout extra to make the Tonerider trt1 fit.

On sanding drum techniques, I like to make strokes/passes to get a relative smooth finishing. No pushing, letting the drum do the work.

Good luck and have fun!

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The end hook on a retractable tape measure is loose so that it should read correctly when
a) hooked over the end of a piece of wood and pulled tight
b) pushed up against an object when measuring from that object e.g. a wall

What you don’t want to do is just place so the end hook is somewhere between the two positions.

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Thanks Simon. You articulated that better than I did.
I should have said that pushed vs pulled tape measurement can vary (eg: overly loose cleat, worn cleat rivets etc).
It's good to check the tape against a steel rule to determine if it's accurate in both directions, and check it periodically.

Side Note:
When I did carpentry as a teenage apprentice (back around the Dark Ages) the boss would get grumpy if you let the tape snap back against the casing! That's exactly how those little rivets get loose and holes in the metal tape get distorted!