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Flat Shim! Why not!?

Discussion in 'Hardware, Setup & Repair [BG]' started by Mili, May 7, 2019.


  1. Mili

    Mili

    Nov 14, 2015
    Earth
    Ok, I have to shim the Neck of my Bass. I need to raise the neck at 16 fret up to 1.5 - 2 mm. I found there are two ways for shimming the neck. 1- Full pocket flat shim 2- Angled shim (I found it should be full pocket too and partial shim at the end of the pocket is a no no and it might lead to ski jump. How to Shim a Bolt-On Neck — Haze Guitars).
    I want to try flat shim because it makes more sense to me. It is easy, no need for calculation and at the first try you are done, Natural(there should be a flat surface of wood in the first place but it machined too much deep in factory so I undo it with a flat shim) but the angled shim is more complicated in calculating and crafting also you may have to do it multiple times( I mean making a shim, put it in the pocket, tighten the neck screws, tune the instrument and nope you should sand it more...)
    Also tilting the neck by an angled shim changes the geometry of the instrument and probably increases the final scale length.
    I see the angled shim has more fans here but no body says what is wrong with a flat shim. Everybody only says you need a much more thinner shim that way(Angled). That's all. I can't consider it as an answer because it's not.
    So what do you think? What's wrong with a Flat shim!!?
     
  2. bpc

    bpc

    Mar 29, 2016
    Central Scotland
    Like you say, a flat shim needs to be thicker. If that isn't a problem for you then there is nothing wrong with flat shims. I've used them myself without issue. Try it and see if it works OK for you. It is easy to undo if there is any problem. Let us know how it works out.
     
    Mili likes this.
  3. Picton

    Picton

    Aug 16, 2017
    Reading, MA
    There are a million threads on this, and you’re WAAAY overthinking it.

    Get a business card (not a credit card). Cut off about 1cm of that card. Take off your neck. Insert your 1cm of business card at the body end of the neck pocket. Reinstall your neck.

    That’s the entire process. I’ve used it a dozen times on basses and guitars, lowered the action, and had no problems with this “ski jump” thing people talk about. If you need more shim, just stack more card.
     
    bigbassmike, JLS and Pilgrim like this.
  4. Mili

    Mili

    Nov 14, 2015
    Earth
    Why not? Too thick or too slippery?
     
  5. Picton

    Picton

    Aug 16, 2017
    Reading, MA
    Far, far too thick.
     
  6. Pilgrim

    Pilgrim Supporting Member

    I second the biz card. A plastic credit card is indeed much too thick. You will be surprised how much difference the thickness of the biz card makes.
     
  7. Mili

    Mili

    Nov 14, 2015
    Earth
    I wanna use a wooden full pocket flat shim!:)
    It seems nobody has a reason against it:cool:.
     
  8. JRA

    JRA my words = opinion Supporting Member

    nothing! nada! flat shims are good! :hyper:


    that said: i use a bit of business card per Picton 's post. good luck with your shimming! :thumbsup:
     
    Mili likes this.
  9. Picton

    Picton

    Aug 16, 2017
    Reading, MA
    Umm. I thought the “against” would be self-explanatory. It won’t tilt the neck, and costs WAY more than a business card.
     
  10. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    It all depends what you are trying to accomplish. The question is why do you need to shim the neck? If it’s because the saddles are as low as they will go and the strings are still too high, an angled or partial shim is the most effective solution. You can use a flat shim, but it will be unnecessarily thick to accomplish the same result. If you are trying to create more space between the strings and the body, a full pocket shim may be a better solution. It all depends on what you are trying to achieve.
     
    Last edited: May 7, 2019
    Nashrakh, Pilgrim and Mili like this.
  11. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    Your reference is incorrect. a ski jump doesn't happen where they are suggesting it could. Their argument for a full length shim is fallacious. You can still do it, but don't do it for the reasons they state. Here's an accurate reference about ski jumps. Getting the Facts about Ski Jumps Knowledge is power.
     
    JLS and Mili like this.
  12. Arie X

    Arie X

    Oct 19, 2015
    fwiw, the utopian shim is a veneer of the same wood that the neck is made from, glued to the tenon of the neck and planed down to the right geometry. clearance holes are drilled through it for your neck bolts. tapered or not it takes time and skill.

    i'm working on a new ibanez right now that has a factory shim (not the first factory shim i've seen) and it's a piece of .010 thick canvas tape stuck into the corner of the neck pocket. i put a dot of super glue under it to keep it in place.
     
  13. JLS

    JLS

    Sep 12, 2008
    Emeryville, Ca
    I setup & repair guitars & basses
    "shim at the end of the pocket is a no no and it might lead to ski jump"

    No.
     
    Picton likes this.
  14. Picton

    Picton

    Aug 16, 2017
    Reading, MA
    I took my JP90 apart and found a factory shim in there: a rectangle of pick material. Looked like Fender light, maybe medium. But it was tort, of course.

    I put it right back where I found it. Bass sounds great.
     
  15. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    Not a fan of tort guards. But shims --- well yah! Imparts a nice vintage vibe to the elevation.
     
  16. Everyone know tort imparts a much better tone when you squish it a little. That’s why tort pickguards can only do so much. :smug::laugh:
     
  17. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    You have revealed the magic of tort. If you squish tortoise you get tort. And therein lies the magic of Motor Town, a.k.a. Motown. It's all in the squishing.
     
    Matt Liebenau likes this.
  18. Back to the original question... I don’t really have any thing unique to add. With the flat shim some people would object to being able to see that comparatively thick piece of wood in the neck pocket unless you can cut it to fit and paint it to match. If the aesthetics don’t bother you then, as @Turnaround said, it depends on why you’re shimming and what you’re trying to achieve.

    Oh, and as was also previously stated, a partial shim does not automatically cause a “ski jump.”
     
    Mili likes this.
  19. megafiddle

    megafiddle

    May 25, 2011
    Flat full pocket shims are used when the neck pocket is not deep enough. This is rarely a problem on commercially built instruments, since that would amount to pretty serious production error. The problem more commonly found in the body/neck fitting is not a shallow pocket, but a slight error in neck angle. And because the amount of error required to cause a neck angle problem is so small, the shim required to correct it is also small.

    If the neck pocket depth is ok, one or two narrow strips of card stock is typically all that's required to correct a neck angle error. To correct the same problem with a flat full pocket shim, the shim would be much thicker and very visible. Plus you would be changing the height of the fretboard above the body, which was likely ok to begin with.

    To effect a certain change in action at the 12th fret, a flat full pocket shim would need to be twice the amount of change required. So a change of 1/32" would require a 1/16" shim.

    -
     
  20. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    I think you mean too deep.
     

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