Just wondering if wine corks are produced in a different way to rod corks? Is the grain in the same direction? If so, I will make a tubular cork borer for the lathe and see what happens.
No difference at all....if they are from decent wine bottles. We get our "grading" of cork from the wine trade, with Flor being the best grade as it has the least amount of voids through it, and thus the least porous for air to get in.
However, like many industries, the wine trade has started to cut costs an improve consistency so use composite cork as it is far easier to control the quality. I presume your corks are proper cork, and if from half decent wine, will be what's known as A grade, possibly AAA.
In years gone buy, this is precisely what rod builders would have used.
If boring holes, a drill press and a jig make life soooo much easier.