Tonerider bridge pick up, scale length and cavity routing

[Johnny Bravo]

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

[dozymuppet]

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.

Sent from my Pixel 4 using Tapatalk

[Johnny Bravo]

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.

[Rodc]

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..

[McCreed]

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

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.

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).

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.

[Simon Barden]

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.

[Johnny Bravo]

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.

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.

[Johnny Bravo]

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

[Johnny Bravo]

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

[McCreed]

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.

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?

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.