Heres the threaded tap from Horizon.
You can do as stated and get a tap for like 3 bucks from Ace,ect...
Or go to one of those low priced tool outlets,H Freight,Auto stores that have the tool display for cheap,ect... and buy a whole tap and die set for under $10.00.
http://www.horizonhobby.com/Products...ProdID=DYN2501