It occurred to me that maybe a good, quick and easy way to create tops would be to use brass pen tubes as the starting piece and to build them up as you go. Using the pen mandrel would allow easy removal and remounting of the top blanks with a fair degree of accuracy. This way you would be able to add all sorts of materials etc, in any order.
Wooden body blanks can be made from flat timber by using a hole saw of any size you chose. Cut almost all the way through and then turn it over and cut through from the other side, this leaves the piece protruding so that it is easier to remove from the hole saw.
Enlarge the center hole to the correct size of the brass tube. Don't forget to roughen up the tube so that you get a good bond.
Glue in the tube. Pen tubes come in a couple of lengths; I suggest using the longer ones as it gives you some extra length to work with.
Mount your blank on the pen mandrel. The adjustable one allows you to keep the length to a minimum therefore helping to control chatter. Turn the base to the shape of your design.
Coloured or resin that has additives in it gives you a big choice of making up bases that are different and unique. An easy mold can be made by boring scrap material with the appropriately sized forstner bit to the required depth.
Casting in the tubes makes the job even quicker and more accurate.
Turn the base to shape.
Picture shows a wooden shaft that has been drilled and glued to the base and tube. The two mating surfaces have to be squared off true to get a good joint. This can be done on the mandrel.
This is a resin filled mold ready to be turned into a shaft and fitted to a base.
(see Making pens My way, on how the molds are made).
The resin shaft is being shaped to a ½ ball shape to fit down onto the top of a base. It is easier to shape the shafts and square the ends before mounting to the base, after which they can be finished to size. Do this on the mandrel of course.
To have a solid shaft of what ever material you chose, turn a short spigot on one end that is a tight fit in the brass tube. Then trim the tube off flush with the base top and glue in the shaft making sure that the joint in nice and square. Alternately you can leave about14mm of tube above the top body then drill into the end of your shaft material that distance and glue it onto the tube and base.
Make up a blind mandrel using a three jaw chuck and a short tight fitting rod, (you will find a drill the right size, use the top end of it) Fit up as illustrated, bringing up the tailstock to centre it all and to give it drive.
You are able to turn a smaller diameter shaft using this method which sometimes looks better.
Now it's time to turn the spinning tip and the cap/finial which are fitted into the tube ends. Turn the spigots a good firm fit in the tubes. There's not much shape latitude with the tips but a whole lot more with the caps/finials.
They will end up looking something like this
All sorts of combinations and designs are there for the making.