Using SONAR Platinum... I could swear I've done this dozens of times in the past with earlier versions...
I have two mono vocal tracks, and I want to comp them into a single mono track. But all I can seem to get is two new mono tracks, so it's as if I've just cloned them. Here's what I did:

1. Selected the two tracks.
2. Clicked Tracks > Bounce to Tracks, which opens the Bounce to Tracks dialog; the tracks I selected are selected in the Source Tracks list; Source Category is Tracks; Channel Format is Mono.
3. Click OK. Track bounce proceeds... when it's done, I have two new mono tracks, not one with two sources bounced together.

What am I missing?
 

When you select Tracks as the source, it will bounce all the tracks to new tracks, so it's like you did nothing but copy the tracks.
Use What You Hear or Buses (presuming you have the vox tracks routed to a single bus).

First what your trying to do makes no sense to me, 
It would be destructive and no way to undue it. 
What your trying to do is mixdwn 2 tracks to one. 
Easy way is just select the 2 tracks and export them as a mono file. 
 
But really I would not choose that as I would be working using take lanes and comping them. 
I'm assuming your wishing to use the best parts of these 2 tracks to make just one vocal right? 

Hello,
you can combined 2 mono to stereo like this.
Create a AUX track and set it to record / set the (output) on the two tracks you want to combined to the AUX track / set pan on each track to the side you want it on, ie. L & R  / hit record.
after you have combined (Recorded) both track / bounce the AUX track.
You will preserve the original tracks as well. :)
 
EDIT:
ALSO:
You can reverse this and take a stereo track and split it into two mono tracks.
Like if you want to do some editing on one side of a stereo track.
 
On the Stereo track create two SENDs to two AUX tracks / set both to record / set one AUX to left mono and one to right mono. And hit record.
Bounce both AUX tracks.

11Dreams
Hello,
you can combined 2 mono to stereo like this.
Create a AUX track and set it to record / set the (output) on the two tracks you want to combined to the AUX track / set pan on each track to the side you want it on, ie. L & R  / hit record.
after you have combined (Recorded) both track / bounce the AUX track.
You will preserve the original tracks as well. :)
 
EDIT:
ALSO:
You can reverse this and take a stereo track and split it into two mono tracks.
Like if you want to do some editing on one side of a stereo track.
 
On the Stereo track create two SENDs to two AUX tracks / set both to record / set one AUX to left mono and one to right mono. And hit record.
Bounce both AUX tracks.

Sounds to me like the most complicated possible way to do that. Anyway, the OP wants a mono track, not stereo.
IMO the roughest way would simply be drag-dropping one track on the other (rec mode Sound on sound, obviously), assuming the volumes and such are ok as they are. And copying them first, if you want to keep separate mono originals.
 

Wow, I can't believe it can be this complicated, I'm quite sure I used to do this fairly often. My ultimate goal was to export the combined track to a WAV file for someone to fly into their version of the project, so I muted everything but the two vocal tracks, exported the entire mix to a mono file, and that gave me what I needed just fine.

You didn't need to mute or solo anything, But you DO need to select the tracks you want to export.
Then choose "Entire mix" from the preset.
 

Kalle Rantaaho

11Dreams
Hello,
you can combined 2 mono to stereo like this.
Create a AUX track and set it to record / set the (output) on the two tracks you want to combined to the AUX track / set pan on each track to the side you want it on, ie. L & R  / hit record.
after you have combined (Recorded) both track / bounce the AUX track.
You will preserve the original tracks as well. :)
 
EDIT:
ALSO:
You can reverse this and take a stereo track and split it into two mono tracks.
Like if you want to do some editing on one side of a stereo track.
 
On the Stereo track create two SENDs to two AUX tracks / set both to record / set one AUX to left mono and one to right mono. And hit record.
Bounce both AUX tracks.

Sounds to me like the most complicated possible way to do that. Anyway, the OP wants a mono track, not stereo.
IMO the roughest way would simply be drag-dropping one track on the other (rec mode Sound on sound, obviously), assuming the volumes and such are ok as they are. And copying them first, if you want to keep separate mono originals.
 

lol... well Gaaaaleee! ;) It may be complicated to some but I see no one else offer a solution.... So, Then just use mono option and don't pan. I offered a solution rather then tell the OP it couldn't or shouldn't be done. lol. Yet, then again that's not even what he wanted to do.  ha! All he had to do was export. So I guess the joke is on me. Again! lol Peace... :)