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Posted: 4/17/2023 9:35:43 PM EDT
It occurred to me to ask: Is the standard "standardized"?

I mean, everyone uses the HUB/Bravo/1.375-24 mount on the can-side. But are the length and class of the male threads the same?

I was looking at SAAMI's barrel thread standardization attempt, and was wondering if there's a similar accepted master blueprint that most manufacturers agree upon "works" in their cans, at least on the male thread pitch and length side of things, but I couldn't find a drawing of even a simple male HUB mount via google image search. Seems like there should be a ton of them out there.

The basic measurements, they all seem to be around .45-.50 deep. It's usually not called out, but the 1.375-24 threads are probably most UNEF 3A.
But from there, there's a lot of variation in the actual adapter lengths, whether someone adds spanner wrench vs. hex flats, the overall diameter of the exterior body of the mount (if it tapers down or not, or has some cosmetic features), some male threads just run out vs. CGS has tapers somewhere down in there, and of course there's going to be the main difference in what flash hider/brake they swallow on the inside (Q, Xeno, direct-thread, ASR, etc.).



VP
Link Posted: 4/18/2023 10:43:11 AM EDT
[#1]
This site will give you specs for the threads, both 2A and 3A (external).

http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx
Link Posted: 4/18/2023 3:30:43 PM EDT
[#2]
The basic measurements, they all seem to be around .45-.50 deep. It's usually not called out, but the 1.375-24 threads are probably most UNEF 3A.
View Quote

Most tubes have more than this for thread depth, so it shouldn't be an issue.
I'd assume class 2 threads, especially for something made by various Mfr's and by an unknown amount of shops.
Link Posted: 4/25/2023 12:07:08 AM EDT
[#3]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Most tubes have more than this for thread depth, so it shouldn't be an issue.
View Quote


I agree that there's not a published agreed-upon length of "the standard" male/female thread interface. A quick google search shows an example of EA calling out exactly a half-inch (class 3) female thread, for instance:



The CGS mentioned in OP has a taper inside the silencer blast chamber to interface with their brand adapter: They assumedly made the female depth pretty long, but if someone made a really realllly long male "HUB" thread, it could run into that taper and end up leaving a gap at the end of the silencer and the HUB mount flange. (*ETA Actually, I don't know if the CGS uses an 1.375 female thread in the can or not, or if that adapter is adapting some other thread pitch TO the 1.375 devices...update if that's the case.)



"The CGS QD Adapter still interfaces with the shallow taper on the Helios core... 1.375x24 pattern QDs from other companies sit on a normal 90 degree shoulder..."

The Rugged RUM, for instance, has a long protrusion poking into the can (and actually looks longer than CGS female allowance – don't know if it is – or if the two diameters interfere or not, though):



vs. YHM Kurz: short as heck (eyeball measurement... ~six turns, but maybe a larger thread relief?)



vs. Dead Air Xeno: (eyeball measurement... ~eight thread turns?)



vs. a JMAC HUB device, obviously with a lot of brake material in front of the (class 2) 1.375 threads, but those threads are a good bit shorter than most others, maybe around... .300 long or so? Might be fine or desireable as they're going to fit anyone's female tube, but conversely not have as much engagement as others.




Welp. No one said HUB was a standard.  :)
Link Posted: 4/26/2023 4:19:02 PM EDT
[#4]
In order to accommodate all the mounts & adapters currently on the market, female Bravo (HUB) needs to be full threads to at least .500" with a bore of at least 1.320" ahead of threads to a minimum depth of .65".

Male threaded Bravo mounts adapters should obviously fit within that.  We make our Bravo adapters with .45" tenons.

Male threads should have a P.D. not exceeding 1.347", female thread minimum P.D. should be 1.349.  We are 1.3450" +.001/-.002 P.D. on Male parts and 1.3500 +.003/-0 on female Bravo parts
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