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Thread: First build: GJB-4

  1. #1
    Join Date
    May 2020
    Sydney, NSW AU

    First build: GJB-4

    Hi all,

    I recently purchased a PB-GJB-4

    Iíve noticed that the body does not have pre-drilled holes for the neck bolt-on, the output jack or the ground wire to the bridge. Is this standard for the GJB-4? I hadnít been expecting to drill these. Can anyone advise what drill bit sizes I should use for the output jack and ground wire? Any tips on how to do it would also be appreciated.

    Iíve also noticed that, although the neck is a nice, tight fit to the body, the neck does not fully recess into the cavity. Thereís a gap of 2-3 mm. I can eliminate the gap by sanding the end of the neck to be more curved. Is there any problem or concern with sanding the end of the neck?

    Iíve attached a photo of the neck/body ďgapĒ along with a photo of the body. Iím aiming for a natural finish - so far, Iíve done one light coat of black, water based dye to make it pop, followed by a light coat of red/brown dye. It looks a little blotchy, but nothing a few more coats wonít fix (I hope). Otherwise, Iíll paint it.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    Overlord of Music Fretworn's Avatar
    Join Date
    May 2013
    Hornsby Area, Sydney, NSW
    Hi Argento and welcome.

    It depends on which factory makes the kits whether these holes are drilled it appears. Iím currently working on a GTB and I also had to drill the ground wire and neck mounting holes in the body. On a JB-style bass the output jack should be in the control plate, so that should be no problem. Itís possible that the factory is dropping the ball on drilling these holes and this could be something Adam will need to look into.

    For the neck mounting holes you need to make sure they are just big enough for the screws to pass through the body without gripping. So they will be a larger bit size than the holes actually in the neck.

    The ground wire hole just needs to be long enough to pass the wire through, but you will need a fairly long bit to drill the distance.

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  3. #3
    GAStronomist Simon Barden's Avatar
    Join Date
    Oct 2016
    Reading, UK
    The initial G in the model seems to indicate a particular factory and whilst their general body construction seems to be of a higher quality, lack of bridge grounding holes does seem to be a speciality of theirs.

    Sanding the end of the neck is fine, as long as you do it before positioning and drilling any holes for the bridge. It's worth checking the fit of the pickguard around the end of the neck as this may cover up the current gap, and if so the pickguard does fit at the moment, it will also need some modification if you reshape the end of the neck.

    Neck screw mounting holes are best done in two stages. First drilling through the body using the neck plate as a guide for screw hole location (you'll be surprised how badly the factories line up screw holes with the holes in the bridge plates on the factory drilled kits, so doing your own if preferable IMO). Use a drill size that's as wide as the screw. You want the screw fitting just fitting through the body without binding at all, so that the screw can always pull the neck down firmly. Ideally use a drill press or drill stand to get the holes vertical, or a metal drill guide if you haven't got those.

    Then you can fit the the neck in the pocket, fit the screws through the holes in the body and use the ends to mark the hole positions on the neck. For the holes in the neck, you'll need a drill bit the same width as the screw body, discounting the thread. You'll need to measure the amount of screw left protruding from the body (not forgetting to fit the neck plate when measuring) and drill to that depth, no more.

    To drill the ground wire hole, you'll need a 300mm long drill bit as you'll need to drill at a very shallow angle and you'll need the drill chuck out of the way. I'd suggest a 4mm drill. First mark out the bridge position and the mounting screw positions, so you know the area where the hole need to go, avoiding any screw holes. Then drill a short vertical hole which you can then position the tip of the long drill in to stop it from skidding off the surface due to the shallow angle.

    Definitely mask off the top to minimise any finish-damaging slips. You'll need to work out the correct angle to drill at, and mark a line on the masking tape that the drill path will take to get to the control cavity rout (you can drill to the bridge pickup rout if this is shorter/easier, but you'll need to be more accurate as to where the hole comes out a sit will need to be low down to stop the ground wire fouling the pickup cover). Using a wooden block of the right height as a support will help to get the drill angle correct. As long as the hole comes out through the side of the control cavity rout, you'll get a wire in it.

  4. #4
    Join Date
    May 2020
    Sydney, NSW AU
    Thanks Fretworn,
    I should have spotted the output comes from the control plate - doh!
    Thanks Simon,
    For the explanation and excellent instructions! I donít have a drill press but found some drill guide options. Iím not too handy so this will be interesting. Will let you know how I go.

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