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How to shim neck to raise it in the neck pocket

Discussion in 'Hardware, Setup & Repair [BG]' started by franvarin, Dec 30, 2017.


  1. franvarin

    franvarin

    May 30, 2013
    Rhode Island
    Hi,
    I just acquired a Fender P bass and have an interesting adjustment I need to make but, I'm not sure how to go about it. The neck is dead straight but, the action is still to high for my liking. The bridge saddles are all the way down basically on the plate. I have another P bass that had the same issue, a local luthier built a shim which just raised the heel of the neck in the neck pocket since the neck angle did not seem to be the issue.

    My question is, I don't see any commercial shims out there that will do the trick. The ones from Stew Mac change the neck angle. So, it seems to me I'll need to create one. Assuming that's true, what material should I use and how think should it be?
     
    Mili likes this.
  2. Picton

    Picton Supporting Member

    Aug 16, 2017
    Reading, MA
    A business card. Just cut it the width of the neck pocket, and round the corners for a snug fit. Use a hole punch to clear the neck bolts. You probably won’t need much more than 1cm of shim.

    Tighten everything down, and if you need more shim stack a second layer of business card. I’ve never needed more than two layers. I’ve done many guitars this way, though I haven’t needed to do my basses. But it’s that simple.
     
  3. Some people recommend wood. Some use a business card. On my own instruments, I've used wood, aluminum sheet metal, and cardboard cut from a breakfast cereal box. I've read that a more dense material acoustically couples the neck to the body better than a lesser dense material that may tend to dampen vibrations that might transfer between those two parts. I don't know or care if that is a real thing or not.
     
    Pbassmanca likes this.
  4. RattleSnack

    RattleSnack Supporting Member

    Sep 22, 2011
    Europe
    There are two ways everyone seem to go. Some people make a wooden "platform" thus raising the neck.
    I prefer tiny shim at the heel, changing the angle. Just 1mm of shim can correct about 3mm at the bridge. If neccesary, you can use it also for a tilt.
    Shim is much simpler, but both methods work. I read interesting research here, sugesting that transfer of the kinetic energy that translates to sound occures via screws.
     
  5. Fender uses some kind of card stock or sand paper? Good enough for me.
     
  6. Picton

    Picton Supporting Member

    Aug 16, 2017
    Reading, MA
    My JP90 was shimmed with a strip of light pick material. I’m not sure if it came from the factory that way, but it works.
     
  7. nervous

    nervous Supporting Member

    Jan 5, 2010
    Beautiful Central, NY
    I once had a bass with this exact condition. It took me a while to arrive at the same solution you're considering because I don't see this specific problem discussed much. The majority of discussion is around a front shim to change the neck angle. Your's is a simple full lift with no angle change. I seem to recall using an expired medical plan card that was big enough to fit the entire cavity yet was slightly thinner than a std plastic CC. I could have easily used a thin wood shim, which I would have probably preferred, but didn't have readily available at the time. My greatest concern was consistant thickness and solid support around all neck screw holes. You're fine either way. Good luck with the fix.
     
    Pbassmanca, franvarin and tlc1976 like this.
  8. musicman666

    musicman666

    Sep 11, 2011
    ca
    Maybe a thin piece of wood veneer cut to shape.
     
    Rallypoint_1 likes this.
  9. Paulabass

    Paulabass

    Sep 18, 2017
    Why not change the neck angle 1/2 a degree? That's the way any good tech will do it. Two layers of business card deep in the pocket.
     
    Killed_by_Death likes this.
  10. Spidey2112

    Spidey2112

    Aug 3, 2016
    IMAG1788.


    After installing a bridge upgrade on a Saga MB-10 kit, I had to shim my neck, as well. The bass body was basswood, so I went to a craft store and picked up a 1/16" thick (2' X 4") piece of basswood. Cut to shape, sanded to match both the pocket and heel, and voila... instant vert, with plenty of 'play' for saddle adjustment height...
     
    Last edited: Dec 30, 2017
  11. tlc1976

    tlc1976

    Aug 2, 2016
    Michigan
    I used a piece of stainless steel but I work in a steel shop so it was easy. Had to use 3/16" on my Harmony bass.

    I agree any piece of highly dense material with uniform thickness will work. I like the old medical card idea.
     
    franvarin likes this.
  12. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    Why the aversion to changing the neck angle? It's exactly what needs to be done. And it's such a tiny change you won't even notice it other than you will be able to set the action lower.
     
  13. 96tbird

    96tbird PLEASE STAND BY

    I once tried a full pocket shim. 2 x .010 maple veneer. Hated it, could always see that gap in the joint. Bad for OCD. Went back to shimming the butt end of the pocket. No gap visible. OCD relief. Plus, a thinner shim needed for the same results: only one thickness of maple veneer required and the result was twice what a double full pocket shim achieved.
     
    megafiddle likes this.
  14. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Remember, if you use a flat shim (constant thickness, full length of the pocket), it will need to be equal in thickness to the amount that you want to raise the saddles. A business card or a 0.010" thick veneer is only going to raise the saddles...0.010", which isn't much. If you need to raise the saddles 1/8" to give them good clearance, you are going to need a 1/8" shim.

    That's why we normally tilt the necks. Adding a small shim at the back of the heel gives you about a 6:1 ratio in the increase in saddle height. A 0.010" shim will get you 0.060" (almost 1/16") of added saddle height. And the change in neck angle is very small (about 0.05 degrees).

    But you can use a flat shim and raise the whole neck up if you want. Usually, the only reason to do that is if something is off in the matchup of the neck pocket depth vs the neck heel thickness, and the strings are too low over the body. In that case you may want to raise the neck for better plucking finger clearance.
     
  15. franvarin

    franvarin

    May 30, 2013
    Rhode Island
    A couple of folks have mentioned this as something to consider. It seems to me the neck is straight but, the neck is sitting very low in t
    @Bruce Johnson ... Thank You for taking the time to explain this! I had not heard the logic behind either approach. At the moment I shimmed the back of the neck pocket with part of an old gift card. It's a little thicker than the business card. But, I have been able to get the action down quite a bit. It is basically at the tolerance that I've seen recommended for Fender Basses. The neck has a little relief so, I don't think there's much more to be done there. I have a little of the neck now showing below the rosewood fretboard. That's what made me initially think the neck needed to come up (full pocket level shim). It still may, I'm going to play the bass for a while and see how the neck stabilizes.

    @Turnaround ... The reason I was trying to avoid just shimming the butt of the neck joint is because I've read some warning about the neck warping over time trying to compensate for the gap created by the shim. To someone who is just learning this stuff, it seems like a reasonable concern. Please correct me if I'm wrong, you folks have been at this a long time and have learned the tricks of the trade including what to and not to do.
     
  16. franvarin

    franvarin

    May 30, 2013
    Rhode Island
    Basswood from a hobby store, that's brilliant! I'm likely going to try a level full pocket shim to raise the neck a bit and see what that does. I'll have to pick some of that from my local hobby store and try it. Thanks for the response
     
    Spidey2112 likes this.
  17. Wood veneer seems to be the best from my experience, but you can use most of the suggested matierials above. However, the veneer seems to be a more permanent fix.

    I would check out the YouTube channel Dave’s World Of Fun Stuff, he discusses all sorts of guitar and bass repair tricks, including shims, in detail.

    Best of luck!
     
    dab12ax7ef and franvarin like this.
  18. megafiddle

    megafiddle

    May 25, 2011
    And that's just to get the saddles up off the bridge plate. If lower string height is needed also, the shim needs to be even thicker. This is often the case, "saddles are decked and strings are still too high".

    Geometrically, a parallel shim needs to be equal to (change in string height at 12th fret times 2) plus change in saddle height.

    So if you needed to raise the saddles by 1/8" and lower strings by 1/16", you would need 1/16" x 2 + 1/8' = 1/4" !

    -
     
    franvarin likes this.
  19. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    That's a myth. If you want more info about it, check this out in the Pro Bench part of the forum...

    Getting the Facts about Ski Jumps

    About half way down that page you will find some info about shims.
     
    Rallypoint_1, Picton and franvarin like this.
  20. mmbongo

    mmbongo Five Time World Champion Supporting Member

    Aug 5, 2009
    Carolinas
    Yep, I use the thin wood veneers available from craft stores...Hobby Lobby or Michaels. You can even cut it with scissors.
     
    franvarin and Spidey2112 like this.

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