Floating bridge in a setup

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ChrisDesign
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Floating bridge in a setup

Post by ChrisDesign » Thu Jun 11, 2020 10:02 pm

How to I ensure my Jazzmaster’s bridge stays straight up in every setup to zero its position for intonation?
"I own a '66 Jaguar. That's the guitar I polish, and baby - I refuse to let anyone touch it when I jump into the crowd." - Kurt Cobain

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timtam
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Re: Floating bridge in a setup

Post by timtam » Thu Jun 11, 2020 10:31 pm

Sufficient string-saddle friction is key to the strings 'gripping' the rocking bridge and moving it the full distance forward/back with trem use, so that it comes back to the upright middle position where it started (where the intonation has been correctly set). String-saddle friction is dependent on string material/coating, saddle material, string-saddle contact area (ie groove shape), and string downforce (string tension and string break angle). So changing any of those in the right direction will increase string-saddle friction. You definitely don't want lubricated saddles on a rocking bridge. The most feasible changes are increased string break angle (higher action or increased neck angle/shim), and increased string tension (ie higher gauge). A buzztop changes just the back string break angle, so it does increase friction, but the imbalance in front/back string break angles may tend to bias the bridge forward of its neutral middle position over time.

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Re: Floating bridge in a setup

Post by ChrisDesign » Fri Jun 12, 2020 2:44 am

timtam wrote:
Thu Jun 11, 2020 10:31 pm
You definitely don't want lubricated saddles on a rocking bridge.
Oops. Off to clean the saddles.
"I own a '66 Jaguar. That's the guitar I polish, and baby - I refuse to let anyone touch it when I jump into the crowd." - Kurt Cobain

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Re: Floating bridge in a setup

Post by jorri » Fri Jun 12, 2020 8:40 am

I've found increased break angle caused it to happen to me. I'm sure it could be either increased or decreased because increasing is more force but decreasing is less moment. Anyway, that would just fiddling with a shim.

I tend to push mine toward the trem, although it can buzz but lifting the trem upwards tends to reseat it.

And yes, you want unlubricated saddles, even worn saddles notched by the string windings. The bridge movement does the work, not the strings moving over the bridge and the strings need to be anchored to it.

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Re: Floating bridge in a setup

Post by timtam » Fri Jun 12, 2020 7:13 pm

ChrisDesign wrote:
Fri Jun 12, 2020 2:44 am
timtam wrote:
Thu Jun 11, 2020 10:31 pm
You definitely don't want lubricated saddles on a rocking bridge.
Oops. Off to clean the saddles.
You do however want a 'free' nut slot, with no string binding. String trees are another potential binding point (the modern styles are smoother than the vintage style in this regard). You want the string moving as freely as possible over all surfaces except the saddles of a rocking bridge.

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Re: Floating bridge in a setup

Post by ChrisDesign » Fri Jun 12, 2020 9:34 pm

Yep, I lubricant my string tree and nut
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Re: Floating bridge in a setup

Post by bodhi » Fri Jun 12, 2020 11:15 pm

I found when I was playing a JMJM for a few months that at least with that guitar (not modded in any way as far as I know, decent set up) it came up a bit sharp after more aggressive trem use. I think I picked it up in a video or something, but I started very slightly to bend down when it was done, and that seemed to ease it back into pitch. Never got around to checking the nut and other things with that guitar, so not sure if it might be possible to fix with setup, but playing technique solved the issue in practice after a while
Jazzmaster project (got a body, placeholder neck, some pickups and ideas)
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Blake Mills-inspired Strat project w/ Gold Foil and slide pickup

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Re: Floating bridge in a setup

Post by timtam » Sun Jun 14, 2020 5:41 am

Just noticed that Fender's setup instruction document for guitars other than teles/strats (which have their own specific instructions), including the jag/jazzmaster, has the recommendation to lubricate all string contact points, including the string-saddle interface.
https://support.fender.com/hc/en-us/art ... -properly-

That is clearly counter to Leo's notion of how the bridge/trem should operate. The original trem patent does talk about some parts needing to be low friction - the conical ends of the bridge supports in the bottom of the thimbles, and the knife-edge/pivot. But he clearly talks about the need for friction between the strings and saddles in order to facilitate bridge rocking ...
"The friction of the strings 13 upon the barrels 63 then causes the barrels 63 to move with the strings instead of sliding relative thereto, so that the barrels and support channel 61 rock with the assemblies 62 about the pivot or fulcrum points at the lower ends of screws 66. Such rocking occurs due to operation of the tremolo device 6 to tension or relax the strings 13, as previously stated."
https://patents.google.com/patent/US2972923A/en

On the other hand, fixed bridges - something that Leo presumably did not anticipate on these guitars - do require low string-saddle friction so that the strings can slide easily over the saddles. So those may benefit from saddle lubrication.

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Re: Floating bridge in a setup

Post by ChrisDesign » Wed Jun 17, 2020 10:46 am

I have lubricated the tailpiece’s knife edge with White Lithium, but never thought to lubricate the bottom of the saddle posts. Something else to do in my next setup.
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Re: Floating bridge in a setup

Post by timtam » Wed Jun 17, 2020 6:42 pm

ChrisDesign wrote:
Wed Jun 17, 2020 10:46 am
I have lubricated the tailpiece’s knife edge with White Lithium, but never thought to lubricate the bottom of the saddle posts. Something else to do in my next setup.
I don't think Leo meant to imply that the conical, pointed tips on the bottom of the bridge height grub screws (or slanted bottom of the thimbles) need lubricating. More so that they were designed that way to be intrinsically very low friction, point bearings. Lubrication won't affect that. Similarly if the trem plate is well made and has the single, clean, symmetrical bearing edges (Fig 4a below) it's probably not likely to be aided by lubrication. They're not sliding surfaces. The forces holding them together are too strong. If they are not articulating properly they need some metal work.
Image
https://patents.google.com/patent/US2972923A/en

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Re: Floating bridge in a setup

Post by ChrisDesign » Thu Jun 18, 2020 1:35 am

Fascinating. The string angle is much higher than that on the Jazzmaster’s original tailpiece location. The angle, instead, matches that of the modern repositioned tailpiece found on the Standard/ Player models.
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Re: Floating bridge in a setup

Post by adamrobertt » Fri Jun 19, 2020 2:48 am

ChrisDesign wrote:
Thu Jun 18, 2020 1:35 am
Fascinating. The string angle is much higher than that on the Jazzmaster’s original tailpiece location. The angle, instead, matches that of the modern repositioned tailpiece found on the Standard/ Player models.
Because the neck is meant to be shimmed and the bridge is meant to be high.

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Re: Floating bridge in a setup

Post by ChrisDesign » Fri Jun 19, 2020 5:52 am

So why don’t Fender shim all Jazzmasters?
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Re: Floating bridge in a setup

Post by adamrobertt » Fri Jun 19, 2020 6:25 am

ChrisDesign wrote:
Fri Jun 19, 2020 5:52 am
So why don’t Fender shim all Jazzmasters?
When Leo designed the Jazzmaster, he was looking at archtops with their long tailpieces and high bridges. He never intended for the bridge to be all the way down to the pickguard - a proper setup (and for the bridge to work) requires a break angle at the bridge that can really only be achieved with the bridge cranked up a bit - and to achieve this and still have a playable action, the neck needs some back angle (around 1 degree in my experience). Fender knew this, and every vintage offset that I've seen has a shim in the neck pocket.

But for some reason this got lost in translation, and many people didn't understand the design. When Fender began reissuing them, they may have even forgotten the best way to set them up - I'm not sure if the first batch of reissue offsets had shims. They may have, but I haven' t owned one.

People tend to think that the only way to lower the action is to lower the bridge, which is what causes so many issues with the vibrato system and bridge that eventually led to people thinking it was a bad design. It isn't a bad design at all - it just is really severely misunderstood. Even today, the offset design being probably the most popular that it ever has been - people still don't understand the system. They think the only way to make a JM playable is to slap a Mastery on it. While they work, it's actually really easy to get a solid, stable setup with even the stock bridge if you know what you're doing.

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Re: Floating bridge in a setup

Post by timtam » Fri Jun 19, 2020 7:52 am

Jazzmasters and jags were originally designed for, and sold with, heavier strings. A 12-52 set has about 50% more tension than a 10-42 set for the same scale and tuning: 67.6 kgf (663N) vs 46.5 kgf (456N) according to D'Addario specs. That translates to a big difference in bridge downforce, and made the force on each vintage saddle/height screws fine for stability. But narrow shims were of course often added at the factory to account for variation in neck/pocket machining, to get the bridge to an 'acceptable' height (we don't know if Fender had a particular number in mind for this).

Zollner quotes 6-7 degs as the vintage JM string break angles he measured (Table 7.1). We don't know if they left the factory that way.
https://www.gitec-forum-eng.de/2019/08/ ... s-on-line/

I have been thinking lately that we need an easy way for players to measure string break angles, so more precise setup information can be offered. eg inexpensive finger goniometer (used to measure finger joints) or inclinometer - see below. Gibson have a tool for measuring neck angles to see if they are within range. I don't know if Fender do. But neck angles can be calculated from some simple measurements and trig ....
https://www.tundraman.com/Guitars/NeckAngle/index.php

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