Suppressors thread pitch ?

[ROLEXrifleman]

OK, don't rape me over this one but I'm out of my league when it comes to this and now that I'm in a CLASS 3 friendly state and I'm getting things together I'm looking for some knowledge.

Please go over with me what I think I know and correct me were I'm wrong.

using the size 1/2 x 28 for these next statements



A) the 1st number, 1/2, represents the MAJOR diameter of the threads. Meaning the absolute top of the threads measured exactly 180 degres from each other ( top and bottom for lack of a better term) in this case the measurment from the top to bottom is .500" or 1/2

B) the second number, 28, represents the actual thread COUNT and not the pitch as commonly said. in this example we would have 28 threads along a 1" run. Obviosly we are talking barrels so 28 threads per inch of barrel.

C) Based on the numbers given the actual thread pitch for a barrel threaded 1/2 x 28 is .0357

D) what thread form is used when threading firearm barrels?

E) The HAND of the thread would be the direction a bolt ( in our cases a flash hider or can) would have to be turned in order to TIGHTEN. generaly speaking this is a RH. Why are there some that use left? Simply to be diffrent? I understand that in some cases you need to use a LH twist because there are rotaional forces acting that would loosen the connection through use, but in suppresor use there are no rotational forces be used, simply linear that could cause the can to loosen, so why not be standardized? damn HK Mark 23

F) Minor diameter would be the actual diameter of the shaft left under the threads?

G) Pitch diameter, do we even need to care?

H) The number of starts, can I assume for what is being talked about here the answer is 1?

I have more questions but I guess we can start here.

as always TIA

 

[ROLEXrifleman]

Re: thread pitch ?

Also, is there a standard for thread depth? I know the formula for minor diamter is major - (depth x 2)

 

[bohem]

Re: thread pitch ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ROLEXrifleman</div><div class="ubbcode-body">OK, don't rape me over this one but I'm out of my league when it comes to this and now that I'm in a CLASS 3 friendly state and I'm getting things together I'm looking for some knowledge.

Please go over with me what I think I know and correct me were I'm wrong.

using the size 1/2 x 28 for these next statements



A) the 1st number, 1/2, represents the MAJOR diameter of the threads. Meaning the absolute top of the threads measured exactly 180 degres from each other ( top and bottom for lack of a better term) in this case the measurment from the top to bottom is .500" or 1/2

<span style="font-weight: bold">Correct.</span>

B) the second number, 28, represents the actual thread COUNT and not the pitch as commonly said. in this example we would have 28 threads along a 1" run. Obviosly we are talking barrels so 28 threads per inch of barrel.


<span style="font-weight: bold">Correct again, a 1/2-14 would be 14 TPI (threads per inch)</span>

C) Based on the numbers given the actual thread pitch for a barrel threaded 1/2 x 28 is .0357

<span style="font-weight: bold">Correct. 28 tpi = 1/28th of an inch between peak to peak</span>

D) what thread form is used when threading firearm barrels?

<span style="font-weight: bold">It's dependent upon the rifling direction of your barrel, but generally you want it to be opposed to the direction of the rifling, so that during the firing cycle it does not spin loose. This generally means to use a LH twist</span>

E) The HAND of the thread would be the direction a bolt ( in our cases a flash hider or can) would have to be turned in order to TIGHTEN. generaly speaking this is a RH. Why are there some that use left? Simply to be diffrent? I understand that in some cases you need to use a LH twist because there are rotaional forces acting that would loosen the connection through use, but in suppresor use there are no rotational forces be used, simply linear that could cause the can to loosen, so why not be standardized? damn HK Mark 23

<span style="font-weight: bold">The rotational forces at work here are not mechanical contact, they are the viscous effects of the gasses burning and coming down the bore</span>

F) Minor diameter would be the actual diameter of the shaft left under the threads?

<span style="font-weight: bold">Correct</span>

G) Pitch diameter, do we even need to care?

<span style="font-weight: bold">Yes, depending upon the thread profile. A standard V-notch generally no, unless it's a precision fit thread. This is where a 3-wire measurement comes in. For a flash hider or suppressor fit, no you don't care</span>

H) The number of starts, can I assume for what is being talked about here the answer is 1?

<span style="font-weight: bold">Correct. A single lead thread gives on a 1/2-28 thread gives you 1/28th of an inch of linear travel per revolution. A double lead (or 2 start) thread would give you 2/28th, or 1/14th of an inch. You would be using a single start thread.</span>

I have more questions but I guess we can start here.

as always TIA </div></div>

I did my best to answer them quickly above.

 

[jscharwath]

Re: thread pitch ?

could someone post the procedure and tools they use to get it right?