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Bridge adjuster at lowest point - need more

Discussion in 'Setup & Repair [DB]' started by warx, Nov 7, 2019.

  1. warx

    warx Supporting Member

    Sep 13, 2010
    Marin, CA
    Hi all,

    Got a Thompson RM100 (ply) Lefty and trying to get my D and G strings a little lower but when I got the bass the adjusters were already at their bottom setting. My strings at the 12th are 8, 7, 7 and 6. The E and A sound good but I think the D and G could improve with lowering I think (Spirocores).

    How much work is it to rework the bridge so the adjusters have some adjusting in both directions? I've worked and built some guitars and am comfortable working with wood - I just would like to know where to remove some height.

    Also, my relief measures 3mm in the center - which seems like a lot no?

  2. A picture would help. It's easy to rework the bridge, in general.
  3. warx

    warx Supporting Member

    Sep 13, 2010
    Marin, CA
    Good point! Attaching...

  4. I got a Thompson RM200 about 8 months ago from Steve at String Emporium.
    Overall I was surprised at how good the set up was as delivered. Like you my bridge adjusters came down to their lowest point. My assumption is this is normal for a new instrument, honestly I’ve never had a a brand new DB before. But as mentioned by Fredrik above, a little bridgework is common work for DB luthiers, I’ve had a bit of shaping and adjustments on other DBs over the years. No big deal...

    My two cents would be to stay with it as for now and see what you think in a couple weeks. Usually measurements for string height are taken at the very end of the fingerboard, but even with the heights you’ve given yours seems within the normal range.

    Otherwise, how you liking your RM100 overall? I’m chuffed with my Thompson choice and really feel they’re a tremendous value in their price range!
    I imagine it must be tough to find many left hand options in the doghouse world.

    I hope you enjoy your bass very much.
  5. warx

    warx Supporting Member

    Sep 13, 2010
    Marin, CA
    True - but I have a lot of relief so was not sure how accurate the end measurements would be. Basically they are same as the heights at the 12th - which shows how concave it is.

    I do think 6mm for the G is a bit high and having some range either way with the adjustors instead of being slammed (bike setup term) would be nice to allow trying a lower height without committing. I've had the bass for two years so it's definitely stabilized and not going to bend out.

    Yes I like the RM100 a lot. Steve found a RM100 and RM200 lefties but unfortunately the hybrid had some damage else I would've got it. Yeah - lefties always a BIG challenge. I was happy to have got at least the RM100. A lot of bass for the price and loved dealing with Steve.
  6. Didn’t realize you’d had your bass for two years already.

    So absolutely! A trip to the luthier for a bit o tweaking might be just the ticket.
    Given your skills, the bridgework may be something you could do yourself, but fingerboard planing is certainly above my abilities.

    It’s REALLY nice to have set up concerns taken care of. god knows there’s enough left on the plate for all the musical efforts that follow.
  7. No problem to sand of a bit at the top. Just make a drawing of the current curve and string slots. You will probably want to make it a bit thinner on the same side, so it's equally thin at the top over all.
    Last edited: Nov 7, 2019
    warx and Fretless55 like this.
  8. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    Fredrik, this may be a dumb idea, but I was thinking that reducing height on the legs just above the adjuster might be the safest way to shorten the bridge and add adjustment space while preserving all of the angles at the top and feet of the bridge. One probably would also need to deepen the adjuster bolt hole in the top leg portion for this purpose.

    Is that approach the wrong way to go?
    warx and Fredrik E. Nilsen like this.
  9. Yes, I was about to suggest that. But as you said: there may be issues with the adjusters length (probably not, but worth checking out first).
    Last edited: Nov 7, 2019
    RBrownBass, warx and dhergert like this.
  10. If the height of E and A is good I would prefer sanding the top of the bridge and leave at least the E as is.
    RBrownBass, warx and dhergert like this.
  11. I’ll be interested in hearing what worked for you.

    All the best!
  12. warx

    warx Supporting Member

    Sep 13, 2010
    Marin, CA
    OK, I'll try the legs first as I can obviously return it to exactly what I have right now by raising it tad. If I feel like lowering the G side more than the E side is excessive and changes the angle I will resort to reshaping the top and keep the legs even.

    Thanks all!!

    If it comes out even slightly uneven, the bridge could be ruined. Those string heights are already low for Spiros. The lower you go, the more you risk buzzing from a bump in the fingerboard you don’t yet know is there.

    If you absolutely must get it lower, buy a set of rattail files and deepen the slots ever so slightly. Take great care to do it evenly, and make sure there are no sharp edges or bends. Put a drop of superglue in each slot and add a tiny bit of graphite powder to make the strings slide evenly, which will help your bridge not to warp.
  14. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    Thank you KFS, I appreciate your correction here regarding my speculation. It's nice to have you guys with experience around!
    KUNGfuSHERIFF likes this.
  15. 9Thumbs


    Jul 3, 2013
    Near Boston
    I removed 3/16 of an inch from above the adjusters on my Thompson. Pretty easy with a good table saw and a sliding jig, but mine were all too high by the same amount. Reshaping a bridge shouldn't be too much of a big deal. Tape a pencil to a dowel and mark the back inside of the bass where the sound post is positioned. Mine didn't fall, but if it happens, it'll be easier to put it back if you know where it was. There are a few videos on Youtube that will teach you how to shape the bridge. I think Upton has one
    robobass likes this.
  16. Brent Nussey

    Brent Nussey

    Jun 27, 2001
    Tokyo, Japan
    I politely disagree. Many years ago, when I switched from gut to steel, Lou DiLeone took the top half of my bridge over to the disc sander, marked how much he wanted to take off, and did it in a matter of about a minute. You just have to make sure you have deep enough holes that the bridge will sit on the adjuster wheels. I think this is way easier to do well than deepening the string slots and the reshaping of the bridge that will be needed as well. If the OP has built guitars before, I'm sure he can do this. The only circumstances where I think it would be better to take the wood from the top is if the legs are very angled (like a Belgian bridge) so that the adjusters would look funny, not sitting centered on the leg anymore, or if there's a lot of wood above the bridge heart, and not much in the legs, and you wanted a brighter sound. I've had a lot of bridges made and modified, and have always noticed less wood above the heart makes for a brighter sound (just my opinion there)

    Of course, if he really wants to change the relative heights of the strings, he has no choice but to reshape. I'd take that to an expert, as it can affect the bowing clearances.

    To the OP, if you can, take enough out so that the adjusters won't be bottomed out any more. Most luthiers agree that it sounds better if there's at least a little space there. Some luthiers also slightly angle the adjusters, that is, the wheels aren't 90 degrees to the flat side of the bridge, for looks. Make sure you get the angle right, and you'll be fine.
    Fredrik E. Nilsen, robobass and neilG like this.
  17. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    In theory I can see both points that have been made about taking material off the legs. The proof is in the physics though. Since I brought up this method in this thread in the first place, I've been exploring the physics involved...

    I'm guessing that the big fear is that the cut angle will tip one portion of the bridge forward or backward, causing the bridge to twist under tension which could be catastrophic in either the short term or the long term. The bridge tipping to the right or left, because one leg is shorter than the other, can be corrected with the adjusters themselves, so that's easier to deal with.

    Ideally there should be some adjustment available with the adjusters though, so that's something that should eventually be corrected, but this project may be best done by a pro. This is not a simple task given the details that have to be just right.

    I'd guess that if the OP is able to use a jig with a table saw or with a belt sander to shorten the legs exactly the same amount and at the exact angle, that's probably the ticket. And again, the holes in the upper legs for the bolts need to be deep enough, so they might need to be drilled deeper.

    In contrast, if the OP is shortening the upper legs by hand with whatever hand tools are available, there will need to be a lot of checking and testing to get the legs exactly the right length with no front or back tilt on either side, in which case it would probably be safer and easier to just adjust the string slot depth instead.

    My DB has a Deuce I bridge with adjusters, but it's a completely different animal than a real wood bridge with adjusters; as such all I can do here is theorize.

    I wish the OP the best, and as mentioned, I appreciate the experience-based wisdom that has been shared regarding how to approach this problem.
    Last edited: Nov 8, 2019
  18. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I second that. Way more precise than a disc sander. Just check first that the holes/threads are deep enough that the pegs/screws won't bottom out. Threads down?
    neilG likes this.
  19. Valid point, I should have added it, but it was late. It's not too difficult to make sure it's even, but it's important. Also, you have to make sure the angle for the adjusters is correct if you remove something from the legs.
  20. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator Gold Supporting Member

    Oct 19, 2000
    Louisville, KY
    This is a very timely thread for me to read because I currently have a student with a bass that needs a new bridge (long story, not worth telling) and who wants to put a Full Circle on it. This student is very hard working and musically gifted but does not have a lot of extra money lying around to pay for bass repairs at this time and the family is not in a position to help with this sort of expense.

    I have an extra nice bridge that came off another bass (another long story not worth telling) that is the same width as the bridge on his bass that I would like to donate to his cause. It was drilled for a FC with 5/16" threads, carefully fitted by great luthiers threads down and so that the feet on the unthreaded side fit perfectly onto the piezo side of the FC adjuster.

    The bridge is too tall for his bass as is, and I was asking myself how to deal with the situation. He probably can't afford to take the bass to the same high rent bass-only luthiers I use out of town, and in town our options are very limited. There is a shop that works on all string instruments for the school system that I occasionally use for seam repairs and the like, so we will likely take the bass there.

    It sounds like given all of the above, cutting down the bridge top to the point where there is a little room to move the adjusters either way would be the best option, no?

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