A lot has been said about the history of Kay basses. Some good information is available here, and here for instance.
I’d like to make some remarks about Kays from a luthier and bassist’s point of view.
The Kay bass is an iconic American laminated bass, at once loved and reviled, and both for good reasons. The affection musicians have for their Kays stems mostly from the fact that the Kay sound is hard to duplicate. It is the sound of Americana of certain genres and eras; the thumpy, percussive, rhythmic baseline that can be heard on so many bluegrass, country, blues and jazz recordings new and old, often came from a Kay. They were made in huge numbers, available then and now relatively inexpensively, and many have stood the test of time with some help from their friends. So what are the downsides of these instruments?
Probably the number one downside is that many of these basses had serious flaws in the craftsmanship of the construction method, and all could be seen to have some basic design flaws that have to be worked around.
Not all Kays were created equal to begin with. The most common flaw is that Kay’s shop foreman was evidently never willing to throw out a batch of hide glue, and never cleaned the gluepot. Some weeks they just keep adding new glue to the old batch, or rehydrated a batch that had been overheated numerous times. The result is that some of these basses were built with glue that had been so abused as to have the basic structure degraded to the point where the laminations of the veneers and other glue joints eventually became more like a loosely associated pile of veneer than any kind of real structure. You can recognize the worst offenders by the many chipped off veneers on the front and back, the veneer separation at the f holes, and the collapsing top arch. Yes, there are ways to rebuild these, I've done a few myself, but if you already have one with this degree of degradation and truly want to restore it, there’s only one person dedicated (mad?) enough to do so, near Asheville NC.
What we do here, is make sure we buy the ones that didn’t have these problems in the first place, because there were plenty of other common flaws to deal with on top of that. The number two problem with these basses is neck issues, and these stem mostly from design problems. Kay necks are slim, both in width, and especially in the depth of the neck and thinness of the fingerboard. Over time, some of them do not have enough “handle stiffness” (the part of the neck that actually has to resist the tension of the strings) to stay straight over time. If you want to understand a bit more about the ideal shape of the fingerboard and neck, you might want to look at my brief article here, but for the moment let’s summarize it this way; too much bend in the neck makes a bass excessively difficult to play with normal tension strings (strings other than guts or “weedwhacker” type nylon strings). Some Kays have adequately stiff necks, and some, particularly some that had maple or even butternut fingerboards, do not. The best solution is normally heat bending the neck and substituting a thicker ebony fingerboard or occasionally we inlay a carbon fiber reinforcing bar into the neck to preserve an existing Brazilian Rosewood board. The other neck issues are breaking through the heel (caused by dropping the bass and aggravated by the neck joint design) and neck joint failures. The bad glue issue can cause a neck joint failure, but the tapered sliding dovetail and choice of poplar as a neck block often cause the neck block to fracture often necessitating a new neck block. Many luthiers engineer the neck joint rather than restore Kay’s original design, for durability, and also because the original neck sets on these basses makes for a shorter than ideal bridge when string heights are dropped to modern standards. Not to mention the overstand.
So the good news is that none of our basses have these problems, and if you’re wondering why our Kays may be somewhat more expensive than the ones on Craigslist, now you start to see why.