How do you run the ground from rear cavity to bridge?

Discussion in 'Luthier's Corner' started by Davemonkey2, Feb 3, 2017.

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  1. Davemonkey2

    Davemonkey2

    Sep 13, 2016
    Central Ohio
    Any tips on drilling a hole from the rear cavity to the bridge in order to run the ground wire? All the instructions I find on installing the pots/knobs say to tighten the bridge on top of the ground wire.
     
  2. It's usually a pretty short hole as the control cavity is pretty close. It's an angled hole so I start by drilling straight down, then once I have that hole established (1/4" deep or so) I angle the drill to go to the cavity. I sand a small spot on the back of the bridge where the ground wire will hit to ensure contact. I lay the wire in place then just screw in the bridge on top of it. I checked for continuity on my first few, but since I've never had a problem, I just do it and assume there is connectivity.
     
  3. bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    What he said, just be careful to get the angle right...
     
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  4. Davemonkey2

    Davemonkey2

    Sep 13, 2016
    Central Ohio
    Thanks!!
     
  5. buldog5151bass

    buldog5151bass Kibble, milkbones, and P Basses. And redheads.

    Oct 22, 2003
    Connecticut
    It's tough to get right - practice on a scrap piece. First time I drilled the ground (was a '51 slab), I went though the back of the bass.
     
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  6. +1 on Jisch's comment. Go to the hardware store and get an aircraft (loooong) drill bit. I think that's what they're called. Should be able to find 1/8" which is more than adequate for a ground wire. I use a piece of plastic to protect the body when you start to drill the angle.

    If it helps, Berry Oakley's "tractor" bass is supposed to have a filled in hole in the back where he drilled for a pickup (I think) wire.
     
  7. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    I also do it the way @Jisch does it, and I make a little ground tail out of a short bit of wire and some copper tape.

    9J7d9Wm.jpg
     
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  8. Obese Chess

    Obese Chess Spicy Big Dad Supporting Member

    Sep 4, 2005
    Portland, OR
    very carefully
     
  9. Scoops

    Scoops Why do we use base 10 when we only have 8 fingers Supporting Member

    Oct 22, 2013
    Sugar Creek, Wisc
    If the control cavity is a bit of a distance to the hole location under the bridge, I've been know to drill a dole from the tail end of the instrument, under the bridge, an then to the bridge pup. The I come back an use a Forstner from the top of the body, down till I come to the first hole I drilled. I plug the hole on the tail end, and mount my strap button to cover the plug
     
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  10. Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yep, these are all methods that I've used. One added safety measure is to set a scrap wood block on the body right beside the drill. On the side of that block, draw the line that describes the angle that you need to drill at, to break into the control cavity, but not go out the back of the body. While drilling, look down the bit to keep it aimed side-to-side. But keep glancing at that line you've drawn on the block, to make sure you stay at the correct vertical angle.
     
  11. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    I just eyeballed it and got away with it by sheer luck and intuition, probably not the best method! I had the insurance of a painted finish in case I screwed it up. Is it not sufficient to just solder an eyelet to the wire end and have a bridge screw run through it for the ground wire? I would think you could experiment with some scrap until you get the angle right, and then use the best resulting scrap as a guide, like a pocket hole jig. Ive done that on furniture projects, odd it never occurred to me on my build.
     
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  12. Radio

    Radio

    Jan 8, 2010
    New Haven, CT
    I screwed this up on a cheap body once, so Bruce has a good tip.
    The long aircraft or bellringer bits are available at Home Depot in 1/8 or 3/16 inch sizes.
     
  13. buldog5151bass

    buldog5151bass Kibble, milkbones, and P Basses. And redheads.

    Oct 22, 2003
    Connecticut
    It doesn't help that long thin bits will flex.
     

  14. Long, thin bits can flex but if the bit is sharp and you don't push too hard and back it out regularly to clear it things will probably be fine. As with any other step exercise patience and caution.
     
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  15. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    SW VT
    From the traditional electronics mindset a ring terminal and a toothed washer (on a mounting screw) would be ideal, but clearly many things work, as the plain wire under the bridge is quite common and few people find any need to "improve" upon it, so it's evidently good enough in most cases, and likely does not need overthinking and overengineering. The toothed washer is a way to get unquestionably firm physical contact that's not easily affected by corrosion, etc. Goes between the terminal and the bridge, if you were of the over-engineering mindset (I may suffer from it.)

    7326.jpg 000-5579-NA.jpg
     
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