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Bridge Setup/Adjustment

Discussion in 'Setup & Repair [DB]' started by zeta, Nov 14, 2000.


  1. zeta

    zeta

    Jun 16, 2000
    Does anyone know where I can find information on adjusting the bridge on my upright bass? I want to lower the action.
     
  2. lermgalieu

    lermgalieu Supporting Member

    Apr 27, 2000
    Palo Alto, CA
    My recommendation would be to find a good luthier. It's worth it.
     
  3. cheapskate

    cheapskate

    Dec 3, 2000
    I want to adjust the action on my bass too. What exactly will a luthier do? - will he "just shave a bit from the top o the bridge"
    The reason I ask is my grandfather repaired a horrible split on the top of my bass perfectly and i think he could sort my bridge out too. (he's a carpenter)
     
  4. Bob Gollihur

    Bob Gollihur GollihurMusic.com

    Mar 22, 2000
    New Joisey Shore
    Big Cheese Emeritus: Gollihur Music
    It's not brain surgery to alter a bridge, but it requires care to avoid complications.

    The one thing to consider is that if you remove the bridge, it's possible that your soundpost will fall -- are you prepared to put it back, and in the right place??

    To try and avoid that complication, lay the bass on it's back (with the back supported, and the headstock not supporting the body-- a dining room table or large couch may do (with the neck hanging off the end). You may even go so far as to stick another bridge or substitute to put some pressue on the belly to help keep the soundpost in place.

    If the present bridge already perfectly matches the contour of your bass' belly, then yes, it is the top that will get the trim. If it does not fit the belly, well, that's a problem for another message.

    DON'T TAKE TOO MUCH OFF!!! It is amazing how much less than a 1/4" will lower the action -- OK - bassists out there who have shaved their bridge resulting in a too low string height, raise your hands (Bob's hand goes up). Be conservative.

    Before the cut put pencil marks at the slots, perpendicular to the bridge attitude. Draw the intended cut with a pencil mark, taking care to maintain the curvature that matches the fingerboard -- or, if it was off, correcting the curve.

    After the cut, notch the new string positions, then sand the fingerboard (top) side of the bridge to curve in towards the top- smooth, but leave the tailpiece (bottom) side at 90 degrees (this helps prevent warp). Finish making neat, round slots to perfectly accommodate the strings' widths.

    If I can make an observation, I often find basses with the string height at the nut being far too high. Changing that isn't brain surgery either. Just be patient and observe the rule that you can always take more wood off, but putting it back is problematic. Investing in a set of needle files at Home Depot ($8) or Sears ($16) is worthwhile.
     
  5. erik II

    erik II

    Jul 11, 2000
    Oslo, Norway
    One question about making new notches in the bridge for the strings: What is the standard value for the distance between the strings, measured from center to center along the curvature of the bridge? Or what references should be used when positioning strings? Fingerboard width? This is tricky to experiment with...

    Thanks for any advices.

    Erik
     
  6. Erik,
    somewhere in Bob´s link page there is a link to general bass measurements ( tried to find it to put the link right here but couldn´t ). There are all the measures including string spacing in the saddle and the bridge.
    If I can remember right, the distance between strings measured from inside is 24,5 mm ( at least I think mine is ).
    That´s easy to measure when you mark the slots to the top.
    Trickier thing is WHERE you mark them, and all I could possibly come up with, after thinking it for a while, was to place the bridge directly to the center of the f-holes, have someone to hold it in place an then using a thread between the saddle and the bridge ( the strings were off ) and judging only with my eyes I marked the E-string slot. After that I measured the other string slots.
    BTW, fingerboard width varies, and in addition to this, if you have a bewel under the E-string, you have to be careful when positioning the E-string and the A-string.

    Bob,
    what I have learned about the "falling soundpost case", is
    that if the soundpost falls down when you loosen the strings, it was too loose in the beginning, and playing the bass would have caused it to wander out of its place anyway.
     
  7. erik II

    erik II

    Jul 11, 2000
    Oslo, Norway
    Thanks Arto, I have a print-out of that list of measures, and it says string spacing 85mm, which gives about 28mm intervals. My strings are now about 25mm apart measured center to center. I don't have a problem with the existing string spacing, but larger intervals might make it easier to bow as the G and E strings would then also be lowered a bit...?

    There is enough space to the edges of the fingerboard (no bevel), and I can also take a bit more off the bridge top. So if I know myself right I won't be able to resist trying it out :).

    Erik
     
  8. Good luck, Erik and remember that you only can loose the price of a new bridge, as well as the work to setup the new one ;-) But that´s how you learn, don´t you think?
    If you don´t want to lower the G & E, you can change the curvature of the bridge top so that they will not come too low. Keep in mind ( if your fingerboard is very flat ) that you have to leave curvature enough to be able to bow...
    Everything you do affects to everything ( am I tryin´ to be filosofical of what? ).
     
  9. Scott Cutrer

    Scott Cutrer Guest

    Aug 21, 2000
    Richmond, VA
    I am in the same boat, but I think I am just gonna buy an adjustable bridge. Bob?
     
  10. Bill Fatty

    Bill Fatty

    Feb 8, 2016
    Al Ain, UAE
    I just did mine! My strings were really high, about 1.2 to 1.8mm from the fingerboard at the end of it. It was quite a job to play it I must say! I (very very carefully) took off the bridge (I was changing the tailwire anyway) and filed the slots down. I angled them ever so slightly so that the point of contact was just at the edge of the bridge (fingerboard side) and with a pencil, coated the slots with graphite. Then I put it all back together.

    Most luthiers and posters seen to recommend removing any excess bridge material so that the slots are no more than 1/3 to 1/2 the string thickness in depth. I haven't done that yet, just waiting to see if it's OK. String height is now abut 7 -8 -9 -10 mm (G to E) from the fingerboard, and it's pretty nice. Haven't lost any volume, in fact it's a lot louder, although that may also be due to switching out the old bit of coathanger that was standing in for a tailwire to a bit of braided steel.

    Actually I was wondering WHY that excess material should be removed - the slots are wide enough do that the strings aren't choked, and the graphite lets them move freely. What's the rational behind this?

    20160218_002136[1].jpg
     
  11. Mark Gollihur

    Mark Gollihur Supporting Member Commercial User

    Jul 19, 2000
    Gloucester County, NJ
    Owner/President, Gollihur Music LLC
    You may change for other strings that are thicker someday, and they'll get choked in the slots.

    But you'll find that as you tune up, the strings "snake" through the slots; if the edges aren't rounded, or are too confining, they can "catch" the edges of the windings and actually grab them - and as you further tune, the windings actually separate, eventually causing the string to become damaged and possibly even fail.
    Also, with shallower holes, you're more likely to have an even surface for the string to sit on; less likely to have a deep "V" shape that could pinch the string.

    It's just good practice. Nice job on the DIY - it's invigorating, isn't it? ;-)
     
  12. Bill Fatty

    Bill Fatty

    Feb 8, 2016
    Al Ain, UAE
    Great, thanks for the info.
    I was an antique furniture restorer in a previous life so a bit of woodwork doesn't faze me! Actually if you see the pic, the E string does indeed have a little "glitch" in the windings. Luckily that was an old string, and I've got a new set on there now.
    So I'm letting it settle in, and letting myself adjust to the new string heights. If I don't feel it needs any more work, I'll shave the extra wood off the top of the bridge, and thin it down a bit. My thinking is to remove material at an angle on the neck side so that the top edge is a bit thinner, and the tailpiece side remains basically flat all the way from strings to top.
    Also, I've learned that the bass is a "pre-glasnost" Strunal 50/1. By reputation it's a bit of a tank, so knowing that I may feel safe in attempting a bit more work here and there, wherever I see it can be done!
    Thanks for the support!
     
    Mark Gollihur likes this.
  13. robobass

    robobass

    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I think the prevailing wisdom here is that the slots should 1: be matched as closely as possible to the string diameter, 2: have a slight roundover on the tailpiece side, and 3: be about a third of the string diameter in depth. I don't personally see any technical problem in having deeper notches, as long as the first two criteria are met. It may be a purely aesthetic thing, but for an aesthetic purist like me, seeing really deep notches on a bass bridge is like getting punched in the ear.
     
    Last edited: Mar 2, 2016
    Mark Gollihur likes this.
  14. Mark Gollihur

    Mark Gollihur Supporting Member Commercial User

    Jul 19, 2000
    Gloucester County, NJ
    Owner/President, Gollihur Music LLC
    That made me snort out loud. So glad I wasn't sipping my coffee!
     
  15. Bill Fatty

    Bill Fatty

    Feb 8, 2016
    Al Ain, UAE
    Well I guess I have bit of carpentry time coming up this weekend! By rounded on the tailpiece side I guess you want the string to have a reasonably sharp "take off " edge on the fingerboard side, am I right? Here's my quick and somewhat crappy sketch of what I think I should be doing to it. Any comments?

    20160303_110343[1].jpg
     
  16. robobass

    robobass

    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    No. You've got it exactly. Good Luck!
     
  17. I would round the slots on both sides equally. Ideally the angle of the string to the bridge on both sides is equal to keep the bridge in place. A sharp edge on the fingerboard side might catch into the windings and separate them. Probably not what you want.
     
    Jake deVilliers likes this.
  18. robobass

    robobass

    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I guess we need a real luthier to chime in here. I always thought that the slot should be linear with the active string length, and break over at the tailpiece side. I'm pretty sure this is how my guy does it, at least.
     
    arnoldschnitzer likes this.
  19. Eric Hochberg

    Eric Hochberg

    Jul 7, 2004
    Chicago
    Get Chuck Traeger's book on bass repair!
     
  20. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Or get a good book.