Double Bass Fingerboard Shim/Neck Angle

[Mike Crumpton]

OK Mike, what trade secret are you referring to?

Bob's best method of shimming a fingerboard. You said' that's not how I'd do it' which implied to me there might be more to come? All this comes from writing a report (whilst at work) and keeping up with my favourite luthier discussions.

I hastily read back the rest of the thread to check I haven't been a total idiot . It may be that it's all done in the same way, so your discussion makes perfect sense - but not to ignorant me. For instance, do you make up a shim off bass and if so how do you get the angle right or adjust it afterwards or even decide what it should be? I note your reply about reshaping the back of the neck afterwards, which implies to me that this should be seen as a more-or-less permanent alteration if it is to be done properly - not a decision to be taken lightly. In that case, the decider needs to know more about the properties of the intsrument and its ability to handle the alteration than assessing the beniefits to playability from the changed angle. You could end up with a super high bridge and raised saddle to lower the tension down to what can be coped with if you were daft enough?

I've learnt so much from you and your luthier colleagues that has helped my understanding of the bass that I'm just greedy to know. Most enlightening are often discussions you have that have no direct relevance to what I'm likely to do to my bass either. If you can stand the grovelling, top luthier contributions make this site truly great for me.

 

[Bob Branstetter]

Bob's best method of shimming a fingerboard.

1. Carefully measure the thickness of the neck handle near the nut and near the end.

2. Remove the old FB

3. If you don' have one, make a jig to determine how large a wedge is going to be required to give you the bridge height you desire. It can be as simple as two 1"x2" boards with a bolt holding them together. One piece is the height of the bridge and the other is the mensur length. Naturally you have to compensate for the fingerboard thickness and desired string height.

4. Make a maple wedge. I have an adjustable jig that I feed thru my overarm router or my thickness sander. The wedge must be evenly tapered and perfectly flat on both the top and bottom with enough extra on sides for later trimming.

5. Do a dry run and remeasure the bridge height to make sure the wedge is the right thickness.

6. Glue on the wedge to the neck with hot hide glue using a heavy flat backing.

7. Attach the fingerboard to the wedge/neck (hide glue).

8. Dress the new fingerboard (and make a new nut).

9. *************************************
Reshape the neck so that it is the same thickness and contour that it was before you added the wedge.
*************************************

10. Reoil neck and fingerboard with a drying oil.

11. String it up.

12. Redo steps 8 and 11 til satisfied.

 

[basswraith]

If one were to use the existing FB that is already on the neck..is it better to plane it down to the desired wedge shape by hand while it is still on the neck or is it better to pop it off and use machines?? . I can see machines making a flatter gluing surface better than a hand plane. And by the way ...now that we are on the subject of angles..what is the desired angle the finger board should project from if the top table is considered ground zero?

 

[Bob Branstetter]

And by the way ...now that we are on the subject of angles..what is the desired angle the finger board should project from if the top table is considered ground zero?

Just where exactly did we get on the subject of angles? If you were making a new neck, the neck angle and overhang would be a consideration. In the case of a wedge to correct a low bridge height, it is meaningless. The correct angle is what ever it happens to work out in the process of projecting the new bridge height. That is why I use a jig.

 

[Mike Crumpton]

Thanks a lot for the reply Bob.

 

[smokinbass]

I know a guy who had a wedge/shim installed on his '39 Kay Swingmaster with great results. The job was considered cheaper and less invasive than a neck reset. However I wonder if the job is done this way and the neck is re-profiled to the original size, would this violate the prime directive because the neck is now thinner and can't be thickened ... say down the road someone wanted to do the neck reset etc. By raising this question I am in no way questioning Bob's methods as I would agree that returning the neck to it's size that it was previous to the wegde/shim job is the right thing to do for the player/owner. Also I wonder about the need for neck resets in general ... is this a by-product of a less than perfect joint ? I feel (don't really know) that with my new block and neck (AS # 787) having a perfectly fit joint that I should not need a reset in my lifetime and possibly the bass will never need it. Also my new neck is thinner than the old one because my new fb is much thicker than the old one. To a blind person the profiles feel identical but I wonder how thin a neck can be before it becomes too thin structurally.

 

[Bob Branstetter]

You raise some valid questions. First you have to remember that my response was directed at a question by Basswraith with regard to a Tyrollean bass. On the typical Tyrollean bass, the upper ribs are actually glued into a trench (perhaps not the best choice of words, but the best I can come up with right now) in the neck so that a neck reset is not a good option in many cases without major modifications. Because of the way that Kays were made, a low bridge problem is almost always the result of a structural problem and IMO the wedge and profile reshape would be simply treating the symptom and not really fixing the problem. The wedge & reshape procedure, like many others, it not something that the novice should consider without consulting with an experienced bass luthier. Only an experienced bass luthier can determine which method is the best to permanently fix a neck problem. Since you mentioned the luthier's prime directive, you should go back to that thread and read Arnold Schnitzer's summary. I think he answered that question far better than I can.