How far apart do you insert the rebar into the old slab and how far do they extend into the new slab. I am assuming that they are epoxied into the old slab? And how deep into the old slab should they go?

You want to put the rebar in about every 8 to 10"(at least), and drill them in as far as the drill bit, at least 8". You want to extend the rebar the legnth of the pour. Epoxy them in tight and tie a few vertical rebars in there. Don't forget to paint on the milky stuff to the old concrete before you pour, that stuff really does make a difference.

I'm a bit late here . 8 " apart is fine. BUT
1. No need to drill in more then 4" deep

2. No need for epoxy.slight horizontal angel when drilling the hole and reverse that angel on every other hole

3. No need to extend that Pined rebar the length of the floor if all you are doing is tying in slab to slab. Cut the stubs 10 to 12" and hammer them in first. Then you can wire tie more rebar on that if you want rebar in new slab.

4. Latacrete (Milk) is a total waste

5. If this is outside a felt expansion joint between the slabs is the proper way. Use construction adhesive to apply "Exp felt" Drill through that for pinning.

21 Boat is right on!!!