12th fret to Bridge/Saddles is longer than 12th Fret to Nut - WTF?

[wokkaboy]

good advice Waz. I suppose first thing we need to establish is what kit Laurie us building and where he has taken his measurements from. I guess it could be different scales between a F, G type and Ibanez scale. My guess being fretless is it's a new jazzy 5 string so whatever a F type bass scale it is.

[wazkelly]

Spot on Woks. Most Bass scales are typically 34" for Long Scale or 30" for short such as on Hoffner & SG shapes but if in doubt the double nut to 12th fret crown measurement works every time.

[laurieb]

Hi Laurie, welcome to the forum, is this a 5 string jazz bass fretless kit ?
You need to measure to the centre of the 12th fret wire, not the dot marker, if you have measured to the marker then please post distances to centre of 12th fret wire.
Usually there needs to be compensation for string widths so distances 12th fret to saddle will be more than nut to 12th fret.

I checked my original measurements against my fender fretless and came up with the correct distance !!
bridge now installed and looks good.
just brain fade and a bit of panic.
thanks for making me think <better if avoided I get into less trouble!!>

thanks laurieb.

[Drashkum]

Sorry for asking a very basic question. I am a first time builder looking for more clarity.

What position should be the saddle in Tom bridge when taking measurement from Nut or from 12th fret.

Should it be as close to the bridge pickup like this?



Or toward the tail piece like this?



Or in middle so that if the intonation goes flat or sharp there can be some compensation on both ways?



I thought middle is fine. But all the videos I see says it should be at top near the bridge pickup. If it is that way, then if the fretted note is flat then how can that be compensated? Or is it usually sharp even at the top point so that all it requires is moving the saddle towards the tailpiece always?

May i know What is the science behind the position


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[Trevor Davies]

The guitar scale length is measured from the fretboard side of the nut to the saddle for the high E string. For the TOM (or any!) bridge the saddles are in a step wise arrangement (see the picture below). The TOM bridge is not parallel to the PUPs to account for the lack of travel (or adjustment) of the saddles.

The actual position of the saddles will depend upon the type of strings used, thickness of the strings used, the height (or action) of the strings from the neck. All these factors will determine the final string length for intonation.

The Science behind it is that when a string is pressed onto a fret (say 12 th), its tension must increase, which increases the frequency of the vibrating string. To compensate for this the string need to be made slightly longer than the scale length. The thicker the string, the greater the change in tension, so the longer the intonation length.

I hope this helps!

[Drashkum]

The guitar scale length is measured from the fretboard side of the nut to the saddle for the high E string. For the TOM (or any!) bridge the saddles are in a step wise arrangement (see the picture below). The TOM bridge is not parallel to the PUPs to account for the lack of travel (or adjustment) of the saddles.

The actual position of the saddles will depend upon the type of strings used, thickness of the strings used, the height (or action) of the strings from the neck. All these factors will determine the final string length for intonation.

The Science behind it is that when a string is pressed onto a fret (say 12 th), its tension must increase, which increases the frequency of the vibrating string. To compensate for this the string need to be made slightly longer than the scale length. The thicker the string, the greater the change in tension, so the longer the intonation length.

I hope this helps!

So is it safe to say that I can glue the neck of the guitar with saddle in midway or 75% towards the bridge pickup?.

I am asking this because I am yet to glue the neck.
When I measure the length from inner side of the nut to crown of 12th fret it comes to 313.5mm

After positioning the neck in neck pocket in such a way that the bottom of the heel is flush with top of humbucker cavity, measurement from 12th fret to the saddle comes to 313.5mm only if the saddle is at top most ( closest to bridge pickup). This would not allow any compensation if fretted note is flat after glueing the neck.

Or in other case I have to move the neck down towards the bridge in such a way that the neck protrudes into the humbucker cavity for couple of millimeters. So that i can reposition the saddle a little bit down to get the 313.5mm on the ruler.

And if I do that i may have to shave / sand the lower wood of neck pickup cavity to fit the humbucker with rings

So i want to know what is the way to get around this


Thank you @Trevor Davies

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[fender3x]

So is it safe to say that I can glue the neck of the guitar with saddle in midway or 75% towards the bridge pickup?...

No. 75% might be OK, but seems too far toward the neck to me. Mid-point is definitely too far back with a TOM. If you have the high E at 313.5 from the middle of the 12th fret (or 627 from the nut...both measurements should be the same, and people seem to do it both ways) it's in the right place. The scale-length is taken from the high E. Once you have the high E in the right place the challenge is to have enough room to intonate the LOW E.

When I measure the length from inner side of the nut to crown of 12th fret it comes to 313.5mm

After positioning the neck in neck pocket in such a way that the bottom of the heel is flush with top of humbucker cavity, measurement from 12th fret to the saddle comes to 313.5mm only if the saddle is at top most ( closest to bridge pickup). This would not allow any compensation if fretted note is flat after glueing the neck.

You are unlikely to need to move it forward if this is the measurement. If you wanted a little forward adjustment, you don't need more than a half turn or 1 turn of the screw. What is more important is that you are able to intonate the other strings. In particular, you need to have enough adjustment way from the nut to compensate for the low E string. This is enough of a problem with TOM's that sometimes luthiers will put the bridge a bit of an angle (low E post slightly farther from the neck) to help compensate for where the low E saddle should be.

Or in other case I have to move the neck down towards the bridge in such a way that the neck protrudes into the humbucker cavity for couple of millimeters. So that i can reposition the saddle a little bit down to get the 313.5mm on the ruler.

You can, but you should not need to. The scale length is determined by the high E string, so it's the other strings that need compensation. If you did need to move the neck a bit toward the bridge, I would suggest checking in your dryfit to make sure the humbucker still has room and the ring still covers the cavity. It probably will for the 1/2mm or less that you might want. You can also expand the humbucker cavity a little to toward the bridge if you need to...but I don't think you'll need to with the measurements you've reported.

And if I do that i may have to shave / sand the lower wood of neck pickup cavity to fit the humbucker with rings

I wouldn't. In fact, I didn't ;-) I had a similar issue with a jazz/ES hybrid bass. You can just push the ring a little toward the bridge if you need to. The pickup ring will be flush with the fingerboard, so no problem there. You'd have to move the ring pretty far for it not to be able to cover the "ears" on the pickup cavity. Also you don't want to mess up the binding ;-)

BTW and FWIW, I just checked the measurement on my Strat, which does have some room to move in both directions. The high E intonated exactly at the nominal scale length.