Threading a muzzle brake for an AR-15

[America Man]

So recently I've been trying to make a muzzle brake. I made my own design and created dimensions for everything and so far everything is going great. My only problem is I don't know how the thread the brake in order to make it sit straight on the gun once tightened. I know it needs a 1/2-28 thread and I'm pretty sure I need to drill the hole a half inch deep but past that I don't know what to do. I'd really appreciate it if I could get some help on this.


p.s. If anyone wants the print for the design I drew feel free to ask. It's not like I have it patented or even know if it works well.

[Sharkbite]

????? You are designing a muzzle break, a part that is subjected to high pressure, and you dont know how to use a tap and die set????

The 1/2 in 1/2x28 is not the depth of the hole.

[America Man]

Originally Posted by Sharkbite

????? You are designing a muzzle break, a part that is subjected to high pressure, and you dont know how to use a tap and die set????

The 1/2 in 1/2x28 is not the depth of the hole.

I know. I'm talking about the hole needing to be a 1/2 inch deep and yes I know it's a 1/2 inch wide tap. I'm talking about getting the thing straight on the gun and not crooked. If you've got nothing useful to say then screw off.

[Scorch]

The work you are asking about is typically done on a lathe, not with a tap.

Turn to dimension (on a lathe)
Drill (on a lathe).
Thread interior (on a lathe, so it is concentric and coaxial to the hole at the front of the brake).
Drill or mill ports (on a mill, so they are consistently angled and radially spaced to the bore axis).

After that, it's all cosmetic (zigzags, skull shapes, spikes, cool logos, etc). But first you have to make the brake so that a bullet won't strike the brake as it exits the muzzle.

It's not like I have it patented or even know if it works well

Working well is the main purpose of a brake. Sure, there are a lot of brakes that just look cool and don't work worth a damn. But why make another?

And BTW, 1/2" of threads really isn't enough.

[Mobuck]

Generally speaking, the through hole and reaming/threading for the muzzle attachment should be the FIRST machining operation

[tobnpr]

I'm currently using a lot of brakes by Harrell's Precision- which are 9/16" thread, tenon length is only .500 max- but thread pitch is 32. The fine threads allow a greater number of threads for engagement, and fine threads are less subject to loosening from vibration than coarse.

The threads do not align the brake to the bore (though they certainly need to be precise). This is done by the shoulder on the brake (typically the rear of the brake, but a shoulder can be internal to bear against the muzzle if needed) being torqued against the barrel shoulder. Both of these surfaces must be machined at perfect right angles to the bore. Assuming you're trying to fit this brake to a factory-threaded barrel, you need to determine the class of thread fit (2A or 3A) by contacting the manufacturer or using wires. Then, the threads could be cut with an appropriate tap.

This is all about clearances. Typically, a brake should bee bored to have 20 to 30 thou clearance over bullet diameter. Any more than that, costs some efficiency. Obviously, the tighter the clearance, the less room for misalignment error.

A flash hider could be threaded by a monkey with vise grips, crooked as hell and there won't be a bullet strike. The longer the muzzle device, and the smaller the clearance, the greater the precision required. An 8" suppressor with tight baffle clearances requires absolute perpendicularity so that baffle strikes do not occur. You must have some way of ensuring that the hole you're drilling/tapping is perpendicular to the brake shoulder- which is why this is best done on precision machinery (lathe or mill).