How do I permanently attach a flash hider to 14.5" barrel? My dad is a machinist and has access to any tools that he would need to do it. I just need to know what to tell him. Do I have him put pins or can we soddier it with regular soddier or is there a special soddier to use. Would lock tight work? Any info would be greatly appreciated and thank you a head of time for your help.

Tell your Dad it needs to be held on with silver solder, he will know what to do from there.

Quoted: There are different types of Silver Solder (different temps), it needs to withstand 1200 degrees or so. Prefered method is to pin it and weld over the pin, the amount of time heat is on the barrel is much less than the Silver Solder method.

+1 TREETOP...

Rtrain, Silver solder is for those that don't have the resources to do the pin and weld method... Because your Dad is a machinist, there's no need to take a chance with the excess heat... Doing the preferred method will be a piece of cake for him  

there's no evidence that the heat from silver solder can do anything as to damage the barrel.  It's a easier/cheaper way and is how many if not most AR venders/manufacturers do it.  Besides you're going to be applying heat when you weld over the pin anyway, which would actually be hotter than silver solder.

Frankly it looks better too, and the barrel threads would be left intact.  And if you ever plan on removing the FS,  silver solder is easier since you don't have to find and drill out the pins.  

Also, a lot of people would fill the threads completely with silver solder.  That's not necessary, you only need a drop or two which would be enough to hold the FS in place permanently.  Again, easier for future removal also should the need ever arise.

Rtrain, just in case your interested, here's the way I do the pin and weld method...

I drill a hole through one side of the FH where the threads are... Then install and time the FH to the barrel... Through the hole I just drilled, I slightly drill into the threads of the barrel. After the pin hole is drilled I insert a steel pin (one that fits snug) into the hole and tap the pin all the way down until it bottoms out... The pin needs to be slightly shorter than the hole is deep (to leave space for the weld)... I then fill the hole with a bead of weld.

 To give it a nice finish, using a lathe, I chuck up the barrel and turn the weld bead down to match the outside diameter of the FH.

To refinish the area that was scared, you can use one of the many spray on & bake on aerosol finishes that are available.