*note:  this is step one for the threaded stoppers as well.

Bring up the tailstock (not shown) and tighten just enough to hold the wood while you turn your design.  At this point I would lightly sand the complete stopper.

Take the design to where you are comfortable parting off.   The top detail in the design  pictured, allows you to finish the complete shape so when you part off, you need only sand a tiny nub on the very top. 

Glue the stainless steel stopper base into the wood with either an epoxy or Tite Bond III.   Many turners use the Tite Bond with great success.   Don't use CA glue as it will break down in time especially with temperature changes if the owner puts it in the fridge.

To make a mandrel or jig, simply turn a piece of scrap wood with a step for the jaw chuck, reverse chuck then turn the top portion.   Drill a 23/64" or 9mm hole through the center and insert a 3/8” x 16 tpi lag or carriage bolt, with a few drops of glue, until it protrudes 1/2" on the front.   There is no limit to the design  or shape of this mandrel, since it  is wood, you can reshape it as you like.  The bolts are available at any hardware store, Home Depot or Lowes.

This picture shows how one woodturner shaped the top of the mandrel to the exact size of the stainless steel stopper so he can see exactly what it  will look like when finished.   

**Note: Follow the first step for the smooth stoppers as shown above  except you would drill a 23/64” hole which is the inside diameter of the threads. Remove the turning blank and insert the mandrel.  This picture shows the bottom of the mandrel with the step for the jaws. 

Thread your turning blank onto the bolt.   There is no need to tap, the wood will thread itself and be nice and tight, although tapping wouldn't hurt.  

There are mandrels on the market that will work with my stainless steel stoppers.   Just check that they are compatible with a 3/8" thread.