Opinions and technique on neck shimming required

[dennispotter]

I have a 69 precision that has a flip up of the neck at about the body joint area, I have worked with the truss rod and have the neck with slight relief, but he flip up necessates the bridge be up high to not buzz, which makes for a high action, higher than desired. I have shimmed the neck in the pocket with sheet metal shims, .020 at the body end and this pretty much does it, but it still needs a high action to stop the flip buzz, although I am contemplating dressing the frets to eliminate the flip. My question, after all this, is what should I use for a permanent shim? I think a maple shim tapered from .025 to .000 would be best for tone. There originally was cardboard used as a shim, but that cannot be best. Are shim materials available or do I have to make my own, I do have a milling machine but holding the maple seems like a problem. I guess I could also set the body up on the mill and machine the "shim out of the pocket, but that doesn't seem like it would be advisable on a vintage bass. Any opinions and/or suggestions?

[AlembicPlayer]

please do not mill the neck pocket of your 69 P bass

dressing the frets, or better yet, PLEK the bass!
once your frets are perfectly level, you can then address the setup, truss etc. After that, chances are you will not need any shim unless there's a problem.

[cynical1]

AlembicPlayer makes two good points...Please Don't mill the neck pocket on your '69 P bass. The other point made is equally as good. Make sure your frets and set-up are good before you started inserts shims. You may be trying to solve the wrong problem.

As far a neck shimming goes...this could get involved...

Over the years I've seen a lot of materials used for shimming a neck. Ideally the shim should be a solid piece of hardwood large enough to fill the entire neck pocket with the taper running down to .000 at the end. This is not always practical as most people do not have access to the stock material or the tools to make such a shim.

The easiest way to make one of these is to find some maple stock and cut it to the size of your neck pocket. Then find a belt sander wide enough to sand the entire piece in one pass. Take some spray set-up adhesive (you can find this stuff in most art supply stores) and glue your shim to a larger, longer board. Now you just take your board, with the shim temporarily glued to it, over to the belt sander and work down the taper. There is a learning curve on this method, so additional pieces of shim material may be required...

And you're right, cardboard is not the best shimming material. The idea of the shim is twofold. One, it sets the proper angle of the neck to allow a more precise set-up. And secondly, it needs to allow as much wood to wood transfer from neck to body as possible. Which effects your tone.

This is where the Micro-Adjust type units, although they're quick and easy, create the most compromise.

If you know your shim thickness then you're set. One trick we used years ago was layering masking tape in the neck pocket until we had the right set-up. Then pull the neck, pull the tape and you have your dimension.

If you don't have access to the tools and stock mentioned above, a good compromise are the 1" strips of veneer tape. (If you can only find the iron on tape then soaking in mineral spirits for a few minutes will release the adhesive to get you back to to wood.) With some time, patience, a little wood glue and some sanding you can achieve some respectable results.

This is just scratching the surface. I'm sure others will have opinions to offer as well.

Happy Trails

Cynical One

[TeleTubby]

All of the above is excellent advice. One more thing to consider is having a tech/luthier remove the offending frets (probably the 15th-20th frets if yours is like mine?), plane the end of the fingerboard surface level again, and re-install the frets. Ideally, this will allow the neck/string/action relationship to return to where it was originally and negate the need for the shim. However, it is probably the most expensive option, if that's a consideration? Someone please correct me if I'm wrong, but I believe the neck bending there is called "tongue rising?" Hope this helps, good luck, and let us know how you proceed.

[Zooberwerx]

The shim is pretty much useless in this situation. The neck has some relief and "tongue lift"; all a shim does is change the orientation of the neck to the body. The neck shape is unchanged but since you've essentially elevated the heel height, you have to raise the string height at the bridge to compensate. Here's a couple of things that might work:

*Remove frets 17-24 (?) and re-plane the FB. Expensive but sometimes necessary, or...

*Agressive fret dressing creating a "drop-off" in the same area. Roger Sadowsky does the same thing when prepping a new bass. Works like a charm in some cases.

Riis

[Jim C]

Brass or other metal shim material can be purchased at mcmastercarr.com
I agree with the above

[GlennW]

I've had success with this for correcting the ski jump at the body end of the neck.

[TeleTubby]

GlennW, very cool set-up. What kind of light are you using and how much heat does it project? And how long does the neck under go the process? Thanks for the pic- I'm inspired!

[Jim C]

Yes, please more details.
I'm ready to fab a neck mount and use my wleding bench for the jig.
Question though; doesn't wood have a memory and that a ski jump will come back over time?