It's not that simple.
With a 3/4 straight bit, the narrowest dado you can cut is 3/4". Given that 3/4" plywood is typically more like 23/32", your 3/4" bit doesn't work in a lot of cases. I mostly use 1/4" and 1/2" bits for dados. If your rabbets on each side the jig's throat are 1/8" then you can use a 3/4" bushing for a 1/2" bit and a 1/2" bushing for a 1/4" bit.
What I did was cut oversized rabbets on the jig (1/4" I think though it might have been 3/16"...) and then put a 1/4" plunge bit in the router and a 1/2" bushing. I adjusted the jig so that the rabbet edges were exactly the bushing width apart (and parallel by doing it at both ends of the channel). Then I plunged and ran the router the length of the channel. That took off just enough to leave a 1/8" rabbet (or lip if you prefer). Viola' - perfect offset.
So, I think you need a 1/2" straight bit. And maybe a 1/4" if you are planning to do smaller than 1/2" dados. Note that no plywood is actually the thickness it's sold as, it's always a tad thinner. I'd probably keep the kit if I were in your shoes
Last edited by PhilBa; 04-14-2015 at 07:12 PM.