Hi Chris

T & G bits are a great tool for the router but they have a great down fall most are 1/4" wide cut the norm and 7/16" deep the norm, if you buy a set that you can use for all jobs from 3/32" to 3/8" wide, the one in the set below comes with a cutter for 1/4" plywood that's always under size the norm..and if you pick up some bigger bearings you can put in a 3/16" to 7/16" deep slot..

11pc 1/2" Shank Slot, Tongue & Groove Router Bit Set - eBay (item 140377742025 end time Feb-01-10 17:04:22 PST)

Katana Slot Cutters, Tongue and Groove Set

Just a note the set from ebay will do the same job as the sommerfeld set but at 1/2 the price plus much more..
http://www.sommerfeldtools.com/3-Pc-Tongue-Groove-Cabinetmaking-Set/productinfo/03004/
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Hi, sounds like you have a bit similar to this one:
eBay Store – Super Carbide Tools: Search results for.

You cut the tongue with the top and bottom cutters then drop the bit height down and cut the groove with the top cutter. All cutters are 1/4", at least on mine they are, so works fine on 1x stock.

 

Yup. More specifically, I have this exact one:

Amazon.com: Porter Cable 2907650 1/2 Inch Shank Tongue & Groove Assembly: Home Improvement

For $5, I figured it was a good buy, even if I have no current plans to use it.

 

Hi Chris - That bit works OK, Think about it though and a 1/4" slot cutter does the same job. Just saves a pass. For $5 I'd have likely bought two of those whether I needed them or not. :sarcastic:

I also have Super Carbides 2-bit wedge T&G set that I like better. Aligns easier in my opinion anyway.