This double bass came in for some setup work a while ago. The obvious areas of attention where the bridge and soundpost, however it also became clear that a fingerboard reshoot would be desirable in order to avoid the chance of buzzing with more comfortable string heights. There was also a loose seam on the bottom bout which was the cause of some buzzes, so I made a few large spool clamps in order to glue that up. (I don’t have basses through the workshop frequently enough to necessitate the purchase or construction of a full set yet!)
All of this was fairly run of the mill, but upon manipulating the bass around whilst the string tension was off, it also became clear the the neck joint was slightly loose. Obviously the string tensions of a bass are fairly large, and the prospect of a neck flying off at some point is definitely not very appealing.
I consulted with the owner, and we decided that it was better to be safe than sorry, so what would make the most sense would be to remove the neck entirely and then re-attach it more securely. This did have the one upside that the fingerboard reshoot is much easier to do when you can hold the neck in the vise versus having to reach around the bass body, so I was glad I hadn’t already started on that!
When I got the neck out, it was rapidly evident why the joint had failed. Disappointingly but unsurprisingly, it turned out that rather than a tapered top block with a recess cut into it to support the neck and provide a solid joint free from left-to-right movement, the neck has just been glued straight to a flat block with not even a cursory mortise, just the ribs sitting loosely again the edges. Additionally, the one gluing surface was in absolutely terrible condition, with rough and lumpy glue acting as more of a barrier to a good joint than anything else.
This required a bit more thought. On a more valuable instrument, one would probably make a replacement top block. (But then also, on a more valuable instrument one would expect to see a less half baked block in the first place.) I decided that the best approach would be as follows:
Clean up the block surface to provide a flat jointing area. Build up the sides of the mortise using shaped blocks so that the neck would be somewhat protected from vertical motion (and also glued over more areas.) Clean up and re-flatten the neck-root itself, which was also not flat (unsurprisingly, given that really terrible selection of wood which was a very unfriendly grain direction and also probably not properly seasoned.)
At this stage I could probably have safely glued the neck back in, however I also know that the owner of this bass does tend to subject it to a bit of wear and tear, lifting it around by the neck etc., so I wanted as safe a joint as possible.
Therefor, I decided to bolt the neck on from the inside as well as a healthy serving of glue. This is probably not something that one would ever consider on a valuable instrument, however in this case and a few others I have found it to be the more time and cost effective way to ensure a stable joint when the surrounding instrument is compromised anyway.
I did this once before on a budget student cello after the neck fell off only a day before the little girl who played it needed it for an important recital. Although bolts and nails seem anathema to the construction of fine instruments in this day and age, it is worth remembering that the vast majority of baroque violins had their necks nailed on for centuries before the modern mortise became de rigueur, and if screws had been affordable in that era then they would probably have proved an even more effective and desirable option due to their easy reversibility.
I think it’s very important to be able to be flexible when taking on big repair jobs, because there is not a one-size-fits-all approach, and what works from a historical conservationist perspective may not work from a practical and financially accessible one.