Anodizing necessary for interior?

[Gator762]

I was thinking the interior anodizing isn't really necessary... Other than for protecting the surface.

I was thinking a P3D bored out to 18mm to accept an 18650 battery would be nice.

 

[Packhorse]

I bored out an IST dive light. Thought it would be easy on my new (no me) sherline lathe. Turned out the torch and reamer wouldnt fit. Any way did it by hand with the reamer and a spanner. Took a while but not a 18650 fits.
I cant see any problem with no anodizing on the interior.

 

[TigerhawkT3]

If you have a cell with a torn wrapper, an anodized interior will help prevent a short. If you're going to expose bare Al, check the cells' wrappings before using them.