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Posted: 9/10/2004 12:12:29 PM EST
I have a post ban upper and am wanting a local gunsmith to thread it. I know that on AR15 barrels, it is 1/2x28 tpi, but is there a certain lenght that the threads are cut from the end of the barrel? I know it has to only be a certain distance so that there won't be threads left after the flash hider is screwed all the way on. I just wanted to print out something if there is a spec or blueprint.

Thanks for any help.
Link Posted: 9/10/2004 4:23:16 PM EST
I use .550 as the length to turn the major thread diamater and then go back and undercut the shoulder square about .040 deep and about .05 wide after I chase the threads. The only reason I chose .550 is because thats what my preban colt upper measured. The rule of thumb on threads is to match thread depth to thread diamater. So a 1/4-20 thread would need at least a .250 thread depth and a 1/2-28 thread would need a .500 thread depth(or thread to thread contact).
Link Posted: 9/11/2004 8:25:20 AM EST
The length of threads should be 0.630" +/- 0.005".

Mike
Link Posted: 9/11/2004 1:27:33 PM EST
Thanks for the info gents!!
Link Posted: 9/12/2004 6:19:16 PM EST
Gang,

Just how stinking hard is is to add threads? Is this a commonly available piece from a Tap and Die operation or does it require a lathe? If a simple thread cutter will do it, got a link?

TIA!

kestrou
Link Posted: 9/12/2004 6:27:06 PM EST
[Last Edit: 9/12/2004 6:27:22 PM EST by mongo001]

Originally Posted By kestrou:
Gang,

Just how stinking hard is is to add threads? Is this a commonly available piece from a Tap and Die operation or does it require a lathe? If a simple thread cutter will do it, got a link?

TIA!

kestrou



At a minimum, you need a lathe to turn the barrel down to ~1/2". From there you may be able to get it with a die, but it is advisable that you use some type of threading guide to ensure your threads are square to the barrel. I made a thread guids, but I used a lathe to make it, so..............
Link Posted: 9/13/2004 9:47:13 AM EST
The die is a a little unusual (for machine threads in general), but is is available at Enco as No. 891-4838. Or at MSC Industrial as No 03934288. Or at KBC Tools as No 1-368-15-28.

But you still need to get the barrel down to 1/2 inch OD to make use of the die.

Good luck.
Link Posted: 9/13/2004 1:41:50 PM EST
Tagged....

I was wondering the same thing...I give a machinest friend a call and see if he can do it easily, if not I may send it away.

FB
Link Posted: 9/13/2004 2:27:06 PM EST
tagged
Link Posted: 9/13/2004 3:29:47 PM EST

Originally Posted By techie123:
The die is a a little unusual (for machine threads in general), but is is available at Enco as No. 891-4838. Or at MSC Industrial as No 03934288. Or at KBC Tools as No 1-368-15-28.

But you still need to get the barrel down to 1/2 inch OD to make use of the die.

Good luck.



techie123 - sounds good, I order stuff from Enco and MSC fairly regularly - think I'll give it a shot - now to start searching for how to disassemble the upper and then headspace it...

kestrou
Link Posted: 9/13/2004 3:42:14 PM EST

Originally Posted By Fat_Boy:
Tagged....

I was wondering the same thing...I give a machinest friend a call and see if he can do it easily, if not I may send it away.

FB



If your friend can chase threads and can take your upper apart it will be easy for him. IF you have a flat top upper and his chuck is big enough the whole upper might fit in behind the jaws making it alot easier since you dont have to remove the barrel.

Or if your in ohio and your friend doesnt come through IM me.
Link Posted: 9/13/2004 3:45:03 PM EST
Also, if you go the die route you will have to undercut the wall where the .50 OD ends so that the FS bottoms out. Otherwise it will not screw all the way on.
Link Posted: 9/15/2004 10:07:22 AM EST

Originally Posted By JohnnyMcEldoo:

Originally Posted By Fat_Boy:
Tagged....

I was wondering the same thing...I give a machinest friend a call and see if he can do it easily, if not I may send it away.

FB



If your friend can chase threads and can take your upper apart it will be easy for him. IF you have a flat top upper and his chuck is big enough the whole upper might fit in behind the jaws making it alot easier since you dont have to remove the barrel.

Or if your in ohio and your friend doesnt come through IM me.



Thanks for the offer, but I am in ME so kind of a long drive. He said it should not be a problem to do.

Not being a machinist type guy this is mostly Greek to me. Is there any particular place to start the threads so a FS w/ a closed bottom "times" correctly when tightened on the crush washer?? I was thinking of getting the YHM-28-5C1, and wanted to make sure the closed portion is not on the 12 o'clock side.

Thanks for the help,

FB


Link Posted: 9/15/2004 5:16:34 PM EST
About the best way to clock a FS in the position you want is to use one or more crush washers. Other than add more washers the only other thing you could do is either shave material from the barrel or FS but thats way overkill. Dont sweat it.
Link Posted: 9/15/2004 7:38:40 PM EST

Originally Posted By JohnnyMcEldoo:
About the best way to clock a FS in the position you want is to use one or more crush washers. Other than add more washers the only other thing you could do is either shave material from the barrel or FS but thats way overkill. Dont sweat it.



Thanks
Link Posted: 9/15/2004 9:41:24 PM EST

Originally Posted By glock23c:
I have a post ban upper and am wanting a local gunsmith to thread it. I know that on AR15 barrels, it is 1/2x28 tpi, but is there a certain lenght that the threads are cut from the end of the barrel? I know it has to only be a certain distance so that there won't be threads left after the flash hider is screwed all the way on. I just wanted to print out something if there is a spec or blueprint.

Thanks for any help.



Mike at American Manufacturing will thread stripped barrel for $35. If you need it removed from upper, etc, then costs are higher. Mike does an EXCELLENT job.

He will also thread 1 barrels for free when you buy one of his Triple X Warrior suppressors...

mark
buda@TripleBreakProducts.com
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