Measure the end of your barrel, the correct thread for AK brakes is 14mm x 1.0 LH, the size before threading should be 14mm or .551 inches, but most that I've measured, including my WASR, are about .548, but they stilll thread fine. You'll probably need more than just the correct die as it's very hard to get the threads started correctly. Kits are made with the die and a thread alignment tool. You'll also need either a muzzle nut or a break to hold the tool on. The kits cost about $60, but there's a guy over on the Guns Network AK boards who's got several kits he rents out for $15 plus shipping on to the next person on the list, his username is WJM. With the kit it's pretty simple to do, takes about 15 minutes and some thread cutting oil. If your barrel is well under the .551 size, then it was probably already threaded and the threads were turned down to make it legal under the AWB. On these I've heard it can be threaded to 1/2 - 28 and an adapter can then be used to mount an AK brake.
