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about shimming a neck

Discussion in 'Hardware, Setup & Repair [BG]' started by mlwarriner, Aug 15, 2005.

  1. mlwarriner


    Nov 8, 2003
    KC, MO, USA
    Okay, so I got my hands on an SX P/J that has neck issues. I've also got a Moses Graphite neck sitting around doing nothing, as I abandoned the project it was purchased for, and nobody here or eBay wants to pay a reasonable amount for it.

    The Moses neck is slightly (about 1/16" give or take) narrower than the pocket on the SX. So I need to shim...

    My questions are: 1. What material should I use to shim with? Wood, plastic, metal, other??? and 2. I'm assuming it would be a good idea to try to shim the neck equally on both sides, as to center it in the pocket as best I can, right? Rather than shim it all the way to one side?

    Please and thanks for any help, guidance, assistance or free beer you have to offer :)
  2. Shimming isn't used for width issues. In fact, on a Fender style bass, a completely tight neck pocket isn't a critical thing at all. Some will disagree but there is little to no sonic coupling coming from the sides of the neck to the body because these two surfaces aren't in compression with each other. It would be much more desireable to have a completely flat bottom in the neck pocket and the clamping surface of the neck. Getting a good mating between these two surfaces is where you get the vibrations back into the body. I always recommend steel inserts in the neck and machine screws through the body for clamping bolt on necks. The multiplied force you can achieve with this setup far surpasses plain wood screws and will give you a tight joint even if the shoulder isn't in good contact with the side of the pocket. When you've seen necks that could be moved side to side in the past, they were screwed (poorly) to the body and you probably couldn't have tightened them much more before the wood would have failed. That's where the inserts help. You'll get about 80 lbs on a single wood screw while you can impart better than 3 times that on a machine screw/insert arrangement.
  3. Groover


    Jun 28, 2005
    Ohio, USA
    Is there some sort of insert you would put in the neck in order to use machine screws?

    Any pics? I'd like to do that, but I have no idea what to look for (at the hardware store).
  4. jja412

    jja412 Fine gear enthusiast

    Feb 2, 2004
    St. Louis
    I've used insert a couple of times (after Hambone's advice) with great results. The first time I just went to the hardware store and bought them. I would advise against this, as the quality on these components at most stores is a little shy of what is desired here. In fact, they were quite flimsy. I ended up buying some good ones from Hambone after a long search. You can PM him to see if he has some left... great guy to deal with.

    Basically you will need two items - Machine bolts to take the place of neck screws, and inserts to set in the neck to mate the bolts for coupling. The insert will have a coarse wood threading on the outside, to embed them in the neck, and a machine threading on the inside, to mate with the neck bolts.

    Here's a pic of the inserts in one of my Warmoth necks:
    As you can see, they have a slot on top for allen wrench to tighten them down. They are pretty easy to do. Just drill the neck to the proper size and depth for your inserts, carefully thread the inserts into the neck, and bolt the neck to the body. Using Hambones advice, I also countersunk the edges to give it a nicer look, and help start the insert.

    The important things to take into consideration:
    1. Drill bit size- to small and the neck with split or crack. This is not considered a good thing. Too big, and the inserts will slip right out. Also not a good thing.

    2. Alignment. - Make sure and line up the holes carefully before drilling, so all the bolts will thread correctly to the inserts. I used a slender punch to mark my hole placement. The neck pocket holes were pre-existing, so I aligned the neck in the pocket, and slid the puch into the hole and tapped it lightly. Then I drilled my holes at the indentation points.

    Should be an easy job. Good luck.

    (Anyone feel free to jump in here, if I missed something.) :)
  5. mlwarriner


    Nov 8, 2003
    KC, MO, USA
    thanks for the help all. the moses neck came with the threaded inserts and machine screws to mount it with. seems that graphite doesn't hold a screw as well as wood, so the inserts are required. in fact, IIRC, the warranty is voided if you DON'T use the inserts.

    so i don't really need to shim side to side huh? interesting :)
  6. I have a P-Bass clone that I put a different neck on. Like yours, there is about 1/32" of slop on each side of the neck pocket. It makes no difference, the bass is just fine. It sustains longer than I need it to, it is extremely stable and I have had absolutely no issues with it. It's counterintuitive, but it's true. By the way, I don't have threaded metal inserts and machine screws and the neck is shimmed!
  7. Yeah, I'm wondering too, where would be the best source for getting those inserts and what length would you all recommend for a standard J-neck (fretless)?
  8. Read ALL of jja412's post again...
  9. Lo, don't misunderstand (or anyone else) - inserts aren't the end all be all for sustain. If your bass already has got what you need then it's not likely anything will make an appreciable improvement. You've also got to take into consideration that the installation of these is not a simple "twist'em in and go" procedure. If you aren't comfortable with tools, this isn't for you and you should let someone else do the work. It is very possible to make a mess of the neck if you don't know what you're doing.

    But, if you've got a dog that has the sustain of floor tom, I can just about guarantee that the inserts will help. If you've got one of those neck/pocket combinations that you just can't seem to keep tight, then I positively guarantee that they'll help.
  10. I understand, Hammy. I was just reinforcing your point that a little gap on the sides of the neck is no big deal.
  11. neilG


    Jun 15, 2003
    Ventura, CA
    McMaster-Carr carries threaded inserts. What is the best thread size? Thanks.
  12. I got your back too! ;) :D