I assume, new drive is properly formated as Journaled HFS with GUID partition table. If so, the best way to do this i to copy whole TM folder structure using sudo in terminal, but if you're not familiar with OSX terminal try to use Disk Utility from you Tools.
1. First turn off your Time Machine,
2. unmount your current TM disk (HD#1), and plug it in, so the system could recognize it as regular drive,
3. open Disk Utility from you Tools, there is Recovery tab (the last one),
4. there you should drag your original TM (HD#1) partition to Source volume box and your new disk(HD#2) partition to Destination box.
5. check "Wipe destination disk",
6. click Recover and wait some time,
7. once it’s done, unplug the old drive and turn Time Machine back on
Other option is to use 3rd party software for disk copying, for example Carbon Copy Cloner.