harry potter - How do the wand makers get the cores into the wands?

One of the sellers of magic wands, Ollivander, sells wands with Dragon heartstring, Phoenix feather, or Unicorn hair cores in them. What does JKR say about how the wandmakers get the core materials into the wands?

Answer

As far as I know there is no canon reference to how the wandmakers get the core into the actual wood of the wand; J.K. Rowling doesn't address this through Pottermore either.

However, I noticed that Ollivander (in the Pottermore links above) references his father 'wrestling' to get the core material into the wand, which would perhaps suggest that the process is difficult. Just as a Harry Potter fan, I would imagine that getting a wand core into a wand is exceedingly difficult and, yes, is a magical process. Too bad it's not detailed further.

The second thing I noticed was under unicorn hair. JKR says that the unicorn hair core is most prone to melancholy (meaning it will mope and die if not attended to on occasion) and must be replaced, so clearly there must be a way, by magic and the wandmaker's skill, to remove a wand core and somehow get a second, new wand core into the wand itself. How this happens, though, at this time is unclear.

Here's a picture from Harry Potter and the Deathly Hallows Part One that shows Voldemort holding Lucius Malfoy's wand as it breaks apart. I don't think the movies are considered primary canon by everyone, but this scene is pretty much the same in the book as it is in the movie. The point is that wand woods are not impervious and they can be breached.