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Posted: 4/7/2026 12:24:13 AM EDT
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Assuming that I'm going to be doing OJT as I try to thread these.... For a tube that I want to thread for a HUB mount.... - What is the maximum ID I should look for? - What is the minimum OD to insure I have enough material to both cut the threads, survive torquing the mount in, and not splitting when fired? What would these answers look like for various calibers and velocities? I imagined there would be a reference published somewhere, but either my google-foo is weak or I suck at search prompt construction. Heck - I had Copilot tell me that you could start with an overly large ID and bore it to a smaller size.... That's how good my searches are. |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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well... Claude is a major dumb-ass. Gemini seems to know what's going on. For machining the HUB (1.375-24 UN) suppressor mount threads, the recommended tube inner diameter (ID) which serves as the minor diameter for the internal threads is generally: - Recommended Inner Diameter (ID) - Target Bore: 1.330" 1.335" - Maximum Limit: 1.340" Note: Machining the ID to 1.330" provides a 75% thread depth, which is the industry standard for a strong, secure fit in materials like 17-4 Stainless Steel or Grade 5 Titanium. Thread Specifications (1.375-24 UN-2B) - If you are single-point threading on a lathe, these are the reference dimensions you'll need: - FeatureDimension (Inches) - Major Diameter (Reference)1.375" - Minor Diameter (Bore ID)1.330" to 1.340" - Pitch Diameter1.3479" 1.3528" - Threads Per Inch (TPI)24 Machining Tips - Material Considerations: If you are using Titanium, aim for the looser end of the minor diameter (closer to 1.335") to reduce tool pressure and the risk of galling during the threading process. - Thread Relief: Ensure you cut a thread relief (undercut) at the shoulder of the internal bore. This allows the HUB mount to seat fully against the shoulder without the thread run-out interfering. - Shoulder Squareness: The "squareness" of the internal shoulder is more critical for suppressor alignment than the threads themselves. - Ensure the face where the mount bottoms out is perfectly perpendicular to the bore to prevent baffle strikes. Common Tools: Most gunsmiths use a 1.375-24 Plug Gauge or a high-quality HUB mount (like a Rearden Atlas or SilencerCo Bravo mount) as a "go-gauge" to verify fitment during the final passes. Recommended Wall Thickness by Material For a tube with a 1.375-24 internal thread (Bore ID of 1.330"), the wall thickness is calculated based on the Outer Diameter (OD).
1. The "Thin Spot" (Thread Valley) - When you cut a 1.375-24 thread into a 1.500" OD tube, your actual "safety" wall thickness is not 0.0625". You must account for the depth of the threads. - OD: 1.500" - Thread Major Diameter: 1.375" - Effective Wall at Threads: (1.500 1.375)/2=0.0625" - his is generally considered the minimum safe thickness for high-pressure rifle rounds when using high-strength alloys like 17-4 PH Stainless Steel or Grade 5 Titanium. 2. Hoop Stress Calculation - The wall must withstand the peak pressure at the "blast chamber" (the area surrounding the HUB mount). For high-pressure rifle rounds (50,000+ PSI), the wall thickness must ensure the material does not reach its Yield Strength. - Thinner walls (0.060") are common for "Form 1" or commercial suppressors to save weight. - Thicker walls (0.090"+) are safer for short-barreled rifles (SBRs) where the unburnt powder and pressure "slap" are significantly higher. Safety Critical Guidelines - Avoid 6061 Aluminum: It is not recommended for high-pressure centerfire rifle suppressors, regardless of wall thickness, as it loses strength rapidly as it heats up. - Internal Shoulders: If you are machining the tube from a solid bar, leave more "meat" (0.080"+) in the blast chamber area and taper the wall thinner (0.050") toward the end cap where pressures are lower. - Factor of Safety: Most designers aim for a 2:1 or 3:1 factor of safety relative to the burst pressure of the tube. |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
|
Here’s a very useful site worth adding to your favorites. https://theoreticalmachinist.com/Threads_UnifiedImperial.aspx |
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