How to do an offline installation of packages in ubuntu 12.04 by exporting this folder /var/cache/apt/*

Suppose I'm on a machine with full internet access and do "apt-get update" it then updates the cache /var/cache/apt/* with binary files.
Now I do a "apt-get install pkgname" and inside /var/cache/apt/archives it places the deb packages.

Now I can consider that if /var/cache/apt/* folder is tarred and exported into a offline machine then "apt-get install pckgname", should install the package. Is this way of package installation valid and if so what should be done additionally to make this thing work?

When I tried this locally, it din't work and every time I did apt-get install pkgname, the my cache-binaries (srcpkgcache.bin, pkgcache.bin) were getting replaced with the default ones.