1. The target date for the upgrade is August 11, 2020. We expect a few hours of downtime during that process. We will post on Twitter and Facebook to keep everyone updated on the progress.
    Dismiss Notice

Turd Polishing - Zinc Block Bridge Repair and Arm Mod

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Multi Angle Vise, Feb 11, 2020.

  1. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Renovating old guitar:


    '80s Korean Strat copy - one task was bridge repair - the block from factory (I'm first owner) looked like this:

    [​IMG]

    One block screw attachment thread is non-existent. The arm hole also completely stripped.


    [​IMG]

    M4 Helicoil to the rescue:

    [​IMG]

    [​IMG]

    Three functional block attachment screws:

    [​IMG]

    Possible reason why stripped from factory - holes in block don't match holes in plate - it's actually impossible to insert an arm:

    [​IMG]



    Plan:
    The arm attachments I like most all have a compressible element to remove slop - mostly Gotoh if I think about it - Edge, GE1996T, 510 etc. Callaham do something similar in the Strat world with the Delrin sleeve. How can I add a compressible element?

    M6 Helicoil to retain arm, and an M5 nylon shoulder washer to support top of arm:

    [​IMG]





    Partway through proceedings:
    • 8mm hole drilled through plate and partially into block to accept shoulder washer
    • 6.2mm hole drilled into block and tapped to accept Helicoil
    • M6 Helicoil just visible at bottom of hole

    [​IMG]


    Success:
    • Arm screws into new stainless spring steel thread.
    • Shoulder washer has been slightly expanded by arm thread (washer ID 5.2mm, arm thread OD 5.6mm).
    • Shoulder washer pulls firmly into 8mm hole and grips arm well.
    • Arm stays where it is put and has zero play.
    • Shoulder washer will be a wear item, I have a bag of them.
    • Shoulder washer still needs shoulder trimming to clear saddle.

    [​IMG]
     
  2. JBG

    JBG Supporting Member

    Messages:
    591
    Joined:
    Sep 2, 2008
    Location:
    Wisconsin
    Nice repair. Good job.
     
    Multi Angle Vise likes this.
  3. Baxtercat

    Baxtercat Member

    Messages:
    12,610
    Joined:
    May 11, 2009
    Location:
    just west of Monterey, CA
    ...and great pix. :)
     
    Multi Angle Vise likes this.
  4. The Pup

    The Pup Supporting Member

    Messages:
    3,233
    Joined:
    Nov 5, 2005
  5. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Slight update - installed.

    Shoulder washer is trimmed to clear the saddle - I cut the shoulder into an octagon in case I wanted to use a small crescent to wind the washer up and down the thread - but it's turned out that I don't need to. The washer draws into the bridge, then binds and stops, while the arm keeps turning into the helicoil below, and through the washer. Removing arm is the reverse, first the arm moves, then at some point the washer releases and comes out with the arm.

    Pretty happy with the outcome, no slop whatsoever, and can leave the arm in any position.

    [​IMG]


    This is a great description of trying to set the outer two pivot screws:

    I went back and forth with this for a while, trying 1/8 of a turn, I did not want to bind the bridge, but I kept thinking I'd left too much clearance.

    This might be helpful for some - I ended up shining a light down the front edge of the bridge, and watching it from underneath the bridge while I adjusted the outer two screws. I could see the gap width very accurately, and be sure the plate wasn't getting jammed against the body anywhere in its travel.

    [​IMG]




    After a bit of use, I removed the arm and thought I'd f#$%ed the threads, as there were bits of metal on the arm.

    Turned out it's just the chrome plating stripping off, the chrome is less flexible than the steel. No copper colour anywhere to be seen, so they presumably skipped that step. Cleaned it up, inspected the helicoil, re-waxed the thread, so far so good.

    The arm is made of softer material than the helicoil - which is good - the replaceable item should wear.

    (BTW the washer is much higher up the arm when inserted.)

    [​IMG]




    I had a GE1996T, a Floyd cutout pickguard, and an '80s Kahler behind the nut string clamp ready to go if this didn't work out, but I think I'll keep it as my last remaining six screw bridge. It's floating such that G goes up a full tone, and I'll never dive bomb it.

    The pivot holes and screws are waxed, a little bit of lube in the nut where it was pinging (yes masking the problem), it's keeping tuning rather well. No string trees.

    I tried the Bonamassa roadie string method that all the cool kids are doing (first time ever - as an experiment), and it's OK, windings are not moving too much on a dip. First impression is it takes longer to settle than the method Frudua uses as there are more windings on the peg that need to bed down. I've been doing it like Frudua since the '80s, I'll perhaps alternate both for a while.
     
    Troglite and walterw like this.
  6. walterw

    walterw Gold Supporting Member

    Messages:
    37,049
    Joined:
    Oct 16, 2006
    having made a short study of the "1 over, 1 under" method and having early on been taught the martin-style lockover thing (what frudua is doing) and thus doing it since forever, i many years ago determined that what works as well if not better is actually simpler than both, namely sticking the string in the hole with enough slack to get maybe 3 winds and then just winding it down the post! every bit as stable. in fact it may be more stable than the over-under, i found that one to be slightly worse, i guess because of the gap left between windings.

    i do bend the leftover bit back against the post just because, something i later learned was known as bill baker's "z bend". i don't bend the string against my thumbnail though, i just slide it back by the same 3-finger distance and bend it against the post itself, same result.
     
  7. walterw

    walterw Gold Supporting Member

    Messages:
    37,049
    Joined:
    Oct 16, 2006
    [​IMG]

    @Multi Angle Vise those aren't stock trem pivot screws! what is that?

    i've thought about this for a while and assuming they're sufficiently hardened steel and long enough to be sturdy in the body, countersunk screw heads actually make way more sense. when you do a hard dive the bridgeplate won't foul against the bottom of the screw head like it does on regular vintage fender screws. i've never tried it for fear it wouldn't "look right" but that doesn't seem too bad. also you need to find screws with a short section of smooth shaft under the head before the threads start.

    (also the helicoil/nylon bushing project is awesome :aok)
     
    Last edited: May 4, 2020
  8. Tone_Terrific

    Tone_Terrific Supporting Member

    Messages:
    31,031
    Joined:
    Dec 26, 2004
    Location:
    Canada-GTA
    Totally.
    Send this tip off to Stew Mac and ask for royalties on a screw replacement kit.
    $10 for the kit and a buck for you.
    Raw materials cost 15 cents. They should go for it.:aok
     
    Baxtercat likes this.
  9. walterw

    walterw Gold Supporting Member

    Messages:
    37,049
    Joined:
    Oct 16, 2006
    they don't look stock so not a chance
     
  10. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Good tip, I'll give that a go.


    Ah, these are something that Saehan and several others in East Asia were doing factory back in the '80s. The holes in the plate are also mildly countersunk. This was my normal, my first exposure to the six screw bridge. They are as you describe, hard steel, short length of smooth shaft between head and thread.

    When I first saw a real Fender, I was genuinely shocked - pan head screws and no countersink??!! As you say, when the bridge goes too far forward, it hits the bottom of the pan head and gets forced down the shaft, entering that Fender hysteresis loop.

    These screws don't have that problem.
     
    Baxtercat and burningyen like this.
  11. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Not content with merely polishing the turd, now gilding. Was curious about these saddles, here was a place to try them.

    They are slightly taller than many Strat style saddles, the minimum string height above bridge plate is ~5.6mm.

    Witness point is at the front edge of the saddle - further forward than most Strat style saddles - so they sit further back on the bridge plate. With spring fully compressed (B & D), witness point is ~25mm from lip at rear of bridge plate. Used silicone sleeve for G, A, low E.

    [​IMG]
     
    walterw likes this.
  12. adrianb

    adrianb Member

    Messages:
    534
    Joined:
    May 30, 2005
    Interesting. How are the string locks? Do they actually improve tuning stability after vibrato use? How wide are the saddles and would you happen to know if they make them in other widths? I can see gaps in between the 6th, 5th, 4th saddles while 1st and 2nd are more snug.
     
  13. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    See this video. They do, but you probably want locking machine heads, or be very careful with wrapping on machine head. Once it's settled in and then locked, G is pretty solid. (The low E was great, but I took the strings off to remove the pickguard, and I'm re-using them, as I'm not burning another set of strings until I'm finished with other bits. The E took a set first time, so when slackened, the windings catch and don't lay down exactly the same on return, I can see it happening. Point is, it's not moving at the bridge, but the other end has to be right as well. G also goes slack on post, but as it's unwound, it generally can slide over itself back to pitch.)


    ~10.6mm wide, I don't think they make other widths, but don't know for sure. I guess they would splay ever so slightly on 10.5mm spacing?


    Yeah it's a bit like that. I could try and make it more even, but that's where they want to be, they will go back there, through combination of intonation screw hole spacing in plate, or spring, or indentations on plate, or who knows? Looks worse blown up. Factory saddles had almost no gap.
     
  14. adrianb

    adrianb Member

    Messages:
    534
    Joined:
    May 30, 2005

    That's really interesting and all, but in the context of a vintage-style 6-screw bridge, which is where my question and interest is coming from, i question the effectivity of those saddles. Wasn't it you or @walterw who used the term "hysteresis" to describe how the movement of a traditional Strat bridge plate would cause the plate itself to "ride" up or down the screws, thus messing up the balance and tuning. After some thought i did see the merits of that idea. Seeing that you have the saddles on a 6-screw bridge, does it somehow change your thinking? (I apologize if it wasn't you!)




    My oddball bridge has old Graphtech saddles that were labeled in the Stewmac catalog as being for PRS, with a 13/32" width (actually around 10.3 mm by my own measurement). And they are side-by-side snug with no gaps.



    Honestly i don't see that as a problem. I believe string tension exerts enough down force to hold them in place anyway.
     
  15. walterw

    walterw Gold Supporting Member

    Messages:
    37,049
    Joined:
    Oct 16, 2006
    Not me, I learned that term myself here, maybe even from @Multi Angle Vise!

    those saddles in fact fix a very real problem, one that’s nigh insurmountable otherwise. When you dive the bridge hard the strings lift up off the saddle, then when you come back up they land in a slightly different spot and get “stuck” there with string pressure, coming back sharp. Usually it’s the low E and plain G that have the most trouble.
     
  16. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Guilty! OK got you now, I see your point.


    To quote back from that thread - the above actually closely approximates what I've got.
    • The plate holes are countersunk from below.
    • The six screws have countersunk heads, so the plate doesn't foul the head, original Saehan.
    • The six screws are on a very slight lean, presumably from 30+ years of pressure, can't imagine Saehan drilled them on an angle. The holes don't look visibly ovalled, but I guess all tolerances are lining up in one direction. Hence the plate is not walking down toward the body.
    I earlier did a bit more examination of it from the side with the pickguard off, wish I'd taken a photo.


    Original Fender style with the pan head screws, if you dive too far, the plate catches on edge of the pan head, gets forced down the screw shaft, maybe touches body, then you do end up in the hysteresis loop. If only ever used for gentle shimmery vibrato, wouldn't be a problem.


    The bridge can even do a mild flutter, but not as good as a two point bridge. If I hadn't got to that stage, I wouldn't have tried the locking saddles on it.


    It was all a bit of mucking around, just to see whether I could overcome its problems sufficiently not to replace it. You may be able to tell from glimpses of the bridge pickup, it's a Dave Murray cosplay guitar now, so I'm kind of happy to keep one last six screw, it looks the part.
     
  17. adrianb

    adrianb Member

    Messages:
    534
    Joined:
    May 30, 2005
    How well do graphite saddles work to address that problem?

    At any rate, i imagine these locking saddles give their full benefit when paired with a knife-edge type bridge rather than the old 6-screw bridge.

    And that's what i've resigned to using my 6-screw bridge for now: gentle up-down vibrato. I believe that's what Leo Fender designed it for anyway. Anything more extreme than that, get out the tuner. I can also do a full pull-up and hold tune -- it's even become a habit to just pull up on the bar at random times and when putting the guitar down.
     
  18. walterw

    walterw Gold Supporting Member

    Messages:
    37,049
    Joined:
    Oct 16, 2006
    graphite and roller saddles sort of work, but with a tone change
     
  19. Badstrat

    Badstrat Silver Supporting Member

    Messages:
    1,281
    Joined:
    Dec 7, 2013
    Location:
    Newcastle,Australia
    Great thread. Is the 3/32” measurement between the trem block and the back of the cavity the correct way set a Fender strat floating bridge? Asking for a friend. Also setting the 6 screws right seems prone to faults. Too loose and the bridge can ride up and down the screws and to tight and movement is restricted when dive bombing.
     
  20. Multi Angle Vise

    Multi Angle Vise Member

    Messages:
    726
    Joined:
    Apr 8, 2011
    Yes to a degree, but would add it depends on whether the plate is truly returning to zero. To expand slightly, the polished turd is now returning reliably to zero, and the strings are locked on the saddles, so there is no tuning instability caused by the bridge. I am not in the hysteresis loop - the screws have countersunk heads, the plate holes are countersunk, the plate is pivoting in place and not sliding up and down the shafts. It can flutter. This is in contrast to the basic Fender design with the panheads - probably wasn't clear in my earlier post. Having said that - you can get a Fender design to flutter, but if you dive too far, you've always got to deal with the panheads pushing the plate down the shaft.

    If the plate is not returning to zero, and has to be reset by compensatory moves, then yes the bridge overall still has a problem regardless of whether the low E & G (particularly) have been helped by these saddles.


    Yes, difficult to get right, have frequently seen it wrong. Way too tight, and you'll be trying to lever the screws out of the body with the arm.

    Mentioned in the other thread, but I think it's useful to study the movement from the side with one spring on the claw and only two strings on the guitar. This reduces the tension enough that you can watch the plate carefully through its range of motion on the screws without strain. Also useful to remove the pickguard, as it obscures the side view, and shine a small light through the plate/body gap to see the clearances.



    3/32" seems awfully little space - is this perhaps between plate edge and body instead?
     

Share This Page