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Backward Bridge Adjusters

Discussion in 'Setup & Repair [DB]' started by Paul Warburton, Jun 2, 2004.


  1. I have been noticing lately alot of people are putting bridge adjusters on backwards. In other words, instead of the threaded part of the wheel going into the upper part of the bridge, i've been seeing the threaded part going into the FEET. What's up with this Luthiers? Is there a reason for this or are these people just dyslexic?
    I've noticed this more on the newer basses ...Eastman in particular. I can't think of any acoustical reason, but what do I know? :help:
     
  2. mxr255

    mxr255 Supporting Member

    Jul 21, 2003
    Williamsport, PA
    I agree Paul. We see this on almost every bass that comes into our shop. We are in the process of carving about 12 bridges for a local school district and all of the old bridges we pulled off were backwards.
     
  3. mpm

    mpm

    May 10, 2001
    Los Angeles
    I've seen the threaded end go through the top of a bass when they're installed upside down! Not good...
     
  4. With the exception of some idiot making them where the threaded part of the adjuster is longer than the legs (as mentioned by Mike P), I fail to see what difference it makes as long as the adjuster is otherwise installed properly.
     
  5. Jeff Bollbach

    Jeff Bollbach Jeff Bollbach Luthier, Inc.

    Dec 12, 2001
    freeport, ny

    It' cuz your from the left part of the country. While our toilets flush in the same directions we here on the right coast install our adjusters threads down.
    Actually, in addition to the reason that our nutlike MPM mentioned, the main reason adjusters were installed in the manner you are used to,[threads up], is due to the actual construction of the adjuster. Up till recent times all adjusters were constructed in basically the same manner. A rod which would be threaded at one end fixed into a disk. If you started with let's say a 1/4 in rod, the threading process would lessen the diameter of that section of the rod. This means that two different drill bits must be used-one to drill the hole that will be threaded and a slightly larger one for the unthreaded part of the rod. The easiest way to accomplsh this is to clamp your undrilled bridge, drill the smaller hole full depth, then switch to the larger bit while the bridge is still fixed and drill a partial larger hole. Now, when you cut off the feet they will be the right size for the untapped portion of the adjuster and you can easily tap the smaller hole leading into the bridge. This process can be reversed but it presents a few different challenges. As a side note I was able to circumvent all these problems and a few more by developing a solid machined adjuster where the unthreaded portion could be milled to a diameter that allowed for only one bit size.
     
  6. I wonder why none of the commercial adjuster are made this way. I've been turning down the unthreaded end of adjusters for years with my little metal lathe. It makes fitting adjusters a lot easier and pretty much eliminates the danger of splitting the bridge legs during the redrilling process. Are you selling any of your adjusters to others?
     
  7. Jeff Bollbach

    Jeff Bollbach Jeff Bollbach Luthier, Inc.

    Dec 12, 2001
    freeport, ny
    I won't sell you any, but I'll connect you with my machinist and also Gasparo[Will de Sola]. Call me.
     
  8. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Sorry, Paul, but I'm on the other side of this issue. IMHO the bridge top needs to sit on the wheel for stability and better sound transmission. Putting the adjuster in threads up also seems to correlate with tilted and warped bridges. To me it's all wrong...and it looks bad, too!
     
  9. Thanks Jeff. I have Will's number.
     

  10. Arnold, I was just kinda throwing this out for you guys to comment...i'm not convinced of either way, but your statement about the stability of the upper part of the bridge laying on the adjuster wheels is one type comment that gives me cause to think about a real good reason for the threads going into the feet.
    Anyway, you, of all people never have to apologize for disagreeing with me! But you didn't anyway and don't ever try it!!
     
  11. erik II

    erik II

    Jul 11, 2000
    Oslo, Norway
    Just wondering... won't there be a bigger risk of the foot splitting with the threaded part going into it (small contact surface, threads pressing partly outwards) than with the wheel resting on top of it (pressure straight down, distributed over a larger surface)?
     
  12. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    No, the bridge foot is actually more massive than the shaft. I've only seen one split foot out of thousands, and it split when the bridge was knocked over. I for one find it amazing that maple can hold threads at all! Yet I've only seen a couple cases of stripped threads, always caused by the adjusters being unevenly set.
     
  13. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    The real risk of splitting comes from removing too much wood in the feet to accomodate a big thread size (Stenholm). I use a 5/16 thread, which seems to be a nice compromise between 1/4-20 and 7/16-18. Unfortunately Fishman ain't makin' a larger thread-size pickup. Oh well; their loss!

    I'm with Ahhnold (Hello, Mr. Treasurer) about the threads pointing down.
     
  14. John Sprague

    John Sprague Sam Shen's US Distributor

    Mar 10, 2003
    Rochester, NY
    Sales Manager, CSC Products Inc.
    We get less wobble with the threads pointing down. Our adjuster is 1/4-20. The biggest problem we see with basses coming in is not the diameter or thread direction, but sloppy workmanship. It's amazing to see the gaps and such that some shops leave, including some guys that I know for certain are very good luthiers. If you're just dying for more to read about adjusters, you can have a glance at our installation method at www.cscproducts.com and choose accessories/adjusters. It's been a nearly never-fail method, and gets you a nice fit.
     
  15. Henry Boehm

    Henry Boehm

    Jun 16, 2004
    Madison, WI
    I've done many 100's of pairs both ways in my shop. Seems like many people prefer to have the threaded portion in the foot. If the adjusters are installed correctly in the first place it doesn't seem to make any difference as far as I can tell. However, if the wheel is riding on the foot, the added friction may increase the chance of the foot moving when rotating the adjuster especially on slick topped instruments. I agree that the biggest problem by far is poorly installed adjusters. And yes: it's really too bad that Fishman didn't use a bigger thread for the Full Circle. I spoke with him about this and he said it was because the majority of adjusters out there thus far have been the 1/4 inch variety...but that seems to be changing fast these days.

    <shameless plug>

    These are my aluminum one piece Double Bass Workshop adjusters (these are made of the rare Mongolian Black Aluminum j/k, they're anodized):
    [​IMG]
    The threads are 3/8-16 and you only need one size drill for installation. I've never split a bridge yet installing these but enlarging existing holes can be treacherous if you don't use the right type of drill bits.
    They're available from International Violin Co.

    Thanks to John Sprague for introducing me to this forum!

    Henry Boehm
    The Double Bass Workshop
     
  16. anonymous0726

    anonymous0726 Guest

    Nov 4, 2001
    Welcome to the hang. There's no shortage of personalities here to keep you entertained.
     
  17. Henry Boehm

    Henry Boehm

    Jun 16, 2004
    Madison, WI
    Heh...no doubt! Thanks for the nice welcome guys!