I figured I'd post what little I know about threading a barrel for a muzzle brake or compensator. I hope this isn't redundant, I just figured it may help someone.
For a long time during the "Clinton Assault Weapons Ban" it was illegal to have a threaded muzzle except on pre-ban rifles. Now that the ban is history most people can legally have threaded barrels (check your local and state laws).
There are three sizes of threads used among AKs that I know of. 14mm, 22mm and 24mm. I've never seen a 22mm threaded barrel or brake so I have to assume they are more rare. The 14mm uses left hand threads, but the 24mm uses right hand threads. I'm not sure about the 22mm.
Most muzzle brakes out there were designed for the older style AK-47 threaded barrel. Therefore the most common thread size is
14mm X 1 Left Hand. In order to thread your barrel to 14mm to accomodate these brakes your barrel must be about
0.52" - 0.58" O.D. This diameter barrel is common among military AKs and SKSs. Muzzle diameters vary among manufacturers, especially with commercial AKs. But most of the military AKs will have the correct barrel O.D. to be threaded to 14mm.
The current military issue brakes on the AK-74s are threaded to 24mm. Here are two pictures comparing a 14mm AK-47 brake to a 24mm AK-74 brake.
Top is 14mm AK-47, bottom is 24mm AK-74. 
Left is 24mm AK-74 brake, right is 14mm AK-47 brake. 
Some of the Romanian rifles had their muzzles turned down so that they couldn't be threaded. I had a 2002 SAR-1 that had the correct barrel diameter. I think a little later they started turning them smaller. I don't know how they do it now that the ban expired.
If you want to use the larger 24mm AK-74 style brakes, you have two choices. You can thread your barrel to 14mm LH and get an adaptor to allow the use of the 24mm brake, or you can buy the whole front sight block/threaded sleeve combo.
The adaptor is available here...
www.ak-103.com and looks like this.
The whole front sight block/threaded sleeve combo is at
www.k-var.com and looks like this.
Another issue is plunger pins. The plunger pin is spring loaded and sticks out of the front sight block. It's job is to catch the brake in the groove and ensure that it can't unscrew and fall off. Plunger pins and springs are available at
www.k-var.com . In order to install one you must remove the front pin that holds the front sight block on, insert the spring and plunger pin into the hole, and then reinsert the front sight block pin. A commercial AK such as a Saiga, Veper etc. probably won't have the plunger pin hole. Here's what I'm talking about.
Here's a picture of the plunger pin with a 24mm brake.
Finally, don't be afraid to thread your barrel. It's very easy. I had never done it before, but I rented a kit and had it done within five minutes without a hitch. Here's what you'll need...
1. Threaded Bore Pilot (TAT)
2. Threading Die
3. Die Handle ... and everything can be found here.
http://www.preciseinnovationsllc.com/threadingkits.htm or you can rent one from someone online like myself.
Good luck on your project
Tat
Die
Handle
Threading Instructions:The Threading Kit contains a THREADING ALIGNMENT TOOL (TAT) that is designed specifically to facilitate the creation of threads on the outside of rifle muzzles that are both concentric and perpendicular to the rifled bore.
Your TAT package contains three parts:
1. Threaded Bore Pilot (TAT)
2. Threading Die
3. Die Handle
Warning: Instructions are for right-hand threading. For left-hand threads, turn the opposite direction.
The TAT is simple to use. Even for the inexperienced, the entire procedure should not take more than five to ten minutes. For your safety, follow these directions carefully:
1. Open the action on the rifle and be sure there is no ammunition in the magazine or the bore.
2. The threading die is split along one side and has screw to adjust the die cut for shallow or deep threads. Open up the die to cut shallow threads in order to start the initial threads on the rifle muzzle.
3. Install the threading die into the die handle. Begin with the large chamfered side facing the muzzle. Insert the die into the handle and tighten the retaining screws so that the die will not turn in the handle.
4. Locate the threaded bore pilot (TAT) and insert the pilot into the threaded die so that the pilot, or the unthreaded end, goes into the die from the side opposite the large chamfer. Turn the threaded bore pilot threads two full turns into the die. Use either your muzzle brake or your flash hider as a jam nut to hold the bore pilot in the die. Tighten firmly.
5. If you have assembled the TAT properly as described above, the die now has about three turns available to cut threads on the chamfer side of the die. The TAT is now ready to use.
6. Hold the barrel of your rifle firmly during the threading procedure. A good bench vice with padded jaws is desirable to hold the barrel. You can use soft wood blocks, sheet lead, or copper sheet as padding for the vice jaws.
7. Lubricate both the pilot and die inside of the muzzle with oil. Now insert the lubed pilot into the bore of the muzzle until the die contacts the muzzle. Grasp die handles in both hands and, using some pressure, rotate the handles in a clockwise direction. You will feel the die start to cut. Keep turning the handles slowly. There should be some resistance until the threading dies bottom out on the pilot (above three full turns).
8. WARNING: When you encounter any resistance, STOP! Do not go any further, remove the TAT, then continue threading. With proper threading, the TAT can last for years. Damaged die can be replaced at the regular price.
9. Leave the die attached to the muzzle. You have established a threading pattern that is both concentric and perpendicular to the bore. Loosen the muzzle brake or flash hider that served as a jam nut and remove the threaded pilot from the die. Grasp the die handle again with both hands, turn the handles clockwise until the die bottoms out against the front sight.
10. Now turn the die handles counter-clockwise and remove the die from the rifle muzzle. At this point, you have established the muzzle threads and all you have to do now is deepen the threads so the muzzle brake will screw on. The pilot is no longer necessary.
11. Remove the threading die from the handle and readjust the die a small amount so that the die will cut slightly deeper threads. Install the die back in the handle. Orient the die so that the side with the chamfer again faces the muzzle. Carefully start the die back on the established threads by turning the die handles clockwise. Continue turning the handles until the die bottoms out against the front sight. Unscrew the die.
12. Try to turn the muzzle brake onto the threads that you cut. If the brake will not start onto the treads, repeat Step # 10 above and try again. You want a good tight fit on the threads with some resistance. You may have to repeat the procedure several times.
13. STOP when you are able to turn the brake on the muzzle at least four or five turns with resistance. Remove the brake from the muzzle. Now take the die that is still installed in the handles and turn the die over. The side with the chamfer should be facing you now. Again, carefully start the die onto the established muzzle threads and turn the die handles clockwise until the die bottoms out against the front sight. Unscrew the die from the muzzle. You are now done threading. Clean any thread cutting from the muzzle threads with a soft wire brush and install the muzzle brake until the base butts against the front sight. Make the unit quite tight.
If you have followed the 13 procedure steps above, your muzzle brake is now properly installed and ready for use. GOOD SHOOTING!
ORIGINAL THREAD SIZESRIFLE CALIBER THREAD SIZE
AR-15, M-16, AR-180 .223 (5.56mm) 1/2x28
AR-15, M-16, AR-180 9mm 1/2x36
Ruger Mini 14 (blue) .223 (5.56mm) 9/16x24
Ruger Mini (stainless) .223 (5.56mm) 9/16x24
Ruger Mini 30 (blue, stl) 7.62x39 5/8x24
HK-91/ G-3 308/ 7.62 15x1
HK-93/ 33/ G-53 .223 (5.56mm) 15x1
HK-94/ MP-5 9mm 9/16x24
US M1/M2 Carabine 30 9/16x24
FN-FAL US Match 308 (7.62) 9/16x24
FN-FAL Para/ SAR-48 308 (7.62) 9/16x24
FN Heavy Barrel 308 (7.62) 11/16x24
STEYER AUG .223 (5.56) 13x1 LH
AKM/ AK-47 0.223 14x1 LH
AKM/ AK-47 7.62x39 14x1 LH
GALIL 308 (7.62) 13x1 RH
GALIL .223 (5.56) 13x1 RH
UZI Carabine/ SMG 9mm 5/8x24
UZI Carabine 0.45
M1A/ M-14 308
L1-A1 308 9/16x24
MAS 1949-56 308 17x1
EDIT: Here are some pics of my theading jobs. Two of these rifles are converted Saigas and the third is a SAR-1.
The Saigas have a "sleeve" around the muzzle which extends from the front sight. That has to be removed in order to thread the barrel. I tried punching out the pins and hammering the front sight off, but it was so tight it wouldn't budge. I ended up cutting the "sleeve" off of one Saiga with a Dremel tool and cutting disc. That was tedius and ended up crooked, requiring a lot of filing. Finally I looked down and noticed a tool under a bunch of junk and it turned out to be exactly what I needed. A pipe cutter! That made it so much easier.
The Saigas muzzle is longer than other AKs. Don't make the mistake of cutting the sleeve back too far or your brake won't screw on all the way. Figure out how much you brake will screw on and only cut the sleeve back that far. I learned this one the hard way.
When you thread the barrel put the kit together like this. Use the brake to firmly hold the TAT in place in the die. It really helps.
Then you just clamp the rifle in a vice and turn the threading kit counter-clockwise until you've threaded it far enough. Easy as pie.
2nd Edit: I was searching for ways to spend my Christmas money and came across something I didn't even know existed.
It's a front sight block with 24mm threads and bayonet lug that's made in the USA for only $25.00! This single product solves several problems at once. If you have a post-ban rifle you can upgrade your muzzle to the proper front sight block, threads, and bayonet lug, while adding a US-made part. If you use a US-made brake that's yet another compliance part added. They also have some very interesting barrel extensions and brakes that I've never seen before.
I apologize if this is common knowledge because it's news to me. I thought K-VARs $100.00 sold FSBs were the only ones available (sold out now anyway). I'm so glad someone took it upon themselves to make this product.
I also found someone in the USA making proper 24mm AK-74 brakes that not only match the real ones exactly, but also come available for the larger diameter 7.62 caliber! I'll share that one as soon as I get mine which is currently backordered. Sorry to be stingy.
Check to make sure wether this counts as a US-made compliance part. I could be wrong about this!http://akpartskits.com/cart/index.php?main_page=product_info&cPath=5_12&products_id=52
