So some of you may remember the pine pineapple made with a [lathe and] 'router crafter' that eventually found service as a stair baluster knob/finial (if not I attach a pic at bottom). When making this using two opposed (left-right) sets of helical grooves I rather liked the effect with only one set (though it is less like a pineapple!). So here is a new finial made of oak with 24 same-sense helical grooves rather than 12 each way. It is smoother than it looks - the finish from the router is quite good followed by a light wire brushing - but it does pick up dust! I will work on this. We quite like it and we wonder about replacing the last of the 3 with a similarly made acorn-in-cup (the originals are somewhat acorn-like oak - see pic). We like the idea of them all being related but different.
As an aside the originals (probably early 20C) are fixed using tapered square forged iron spikes, complete with barbs, driven into holes. This seems to work and may be typical of the time. I have gently levered off the original finials and then made a new base that is then similarly driven on (see pic) before the top is glued on. The finial and base are both oak but I have re-used the first zebrawood top from the pineapple (changed for a more leaf-suggestive version on the pineapple).
PS - note that the base has cracked between the time it was fixed (pic 3) and now. I guess the problem with this method of fixing although my hole is a bit bigger than the original. It still seems pretty firm, though.