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Thread adapter for supressor - process discussion

skelso

Plastic
Joined
May 29, 2014
Location
Bryan
A friend (fellow smith) and I have been having a discussion about something today and I thought I would put it out there and ask for your thoughts and comments.

I am not a fan of running a thread adapter with a supressor but I have a few guns that require them. I purchased commercially available adapters for those. Now I find myself in need of another one and decided to make it.

I have a direct thread supressor rated or 300 win mag (AAC 300TM) that I would like to run on my 7mm Mag. Problem is barrel profile will not allow me to thread 5/8 without cutting it much shorter than I am willing. The barrel is currently threaded 7/16 for a muzzle brake. The threads are concentric with the bore (I'm positive because I cut them myself).

My plan is to dial in a piece of 4140, drill, single point internal threads, single point external threads, and knurl a short section all without removing the work piece from the chuck. I contend that the internal and external threads will be concentric to one another so long as the work piece is not moved between operations.

My buddy thinks I need to drill, cut the internal thread, screw it on the barrel, dial it in, then cut external diameter & threads.

I would rather not use his method if I don't have to because I will have to pull my optic so I can get enough through the spindle.

What am I missing here?





Sent from my SAMSUNG-SM-T377A using Tapatalk
 
A friend (fellow smith) and I have been having a discussion about something today and I thought I would put it out there and ask for your thoughts and comments.

I am not a fan of running a thread adapter with a supressor but I have a few guns that require them. I purchased commercially available adapters for those. Now I find myself in need of another one and decided to make it.

I have a direct thread supressor rated or 300 win mag (AAC 300TM) that I would like to run on my 7mm Mag. Problem is barrel profile will not allow me to thread 5/8 without cutting it much shorter than I am willing. The barrel is currently threaded 7/16 for a muzzle brake. The threads are concentric with the bore (I'm positive because I cut them myself).

My plan is to dial in a piece of 4140, drill, single point internal threads, single point external threads, and knurl a short section all without removing the work piece from the chuck. I contend that the internal and external threads will be concentric to one another so long as the work piece is not moved between operations.

My buddy thinks I need to drill, cut the internal thread, screw it on the barrel, dial it in, then cut external diameter & threads.

I would rather not use his method if I don't have to because I will have to pull my optic so I can get enough through the spindle.

What am I missing here?





Sent from my SAMSUNG-SM-T377A using Tapatalk

Either way would probably work fine, but your buddy's answer is "more correct". Threads really aren't for alignment and where alignment is truly critical some sort of alignment boss should be used in conjunction with the threads - kind a like a shoulder bolt going into a counter-bored hole.

GsT
 
GsT is correct. The threads of threaded parts always have some play, otherwise they would be a press fit. A registration feature such as a matching taper or stepped shoulder is needed to center it.

If you want to prove it to yourself, mount a piece of scrap and clean up the outside so it's the same diameter from end to end. Turn the end for a 7/16th screw, then single point it. Part it off and bore the remaining piece for 7/16 internal thread and single point that. Theoretically you now have a bolt and screw that have outer surfaces that are perfectly aligned. Screw them together and I bet that the joint will be off enough to catch a finger nail, maybe even as much as several thousandths of an inch.
 
Makes sense. Guess I won't take the lazy way out... Thanks for the replies Y'all!

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