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Rifles, Reloading, Optics, Equipment
Gunsmithing
Stub acme thread for barrel / action mounting
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<blockquote data-quote="HarryN" data-source="post: 980370" data-attributes="member: 69773"><p>Thanks for the reply.</p><p> </p><p>I could be wrong, but I think it would only make sense to make the thread stub acme if this was the plan for both parts (action and barrel) from the beginning, not as a re-thread.</p><p> </p><p>The typical reasons that acme / stub acme type threads are used are:</p><p>- The root of the acme thread is wider, so the individual threads are stronger. On a stub acme, this is even more the case.</p><p>- The traditional threads tend to have sharp / narrow edges, which can become stress concentrators. If there is plenty of material it probably does not matter, but if the barrel / action area is getting thinner, this might be a factor.</p><p>- Acme are often made to be self centering, which can increase assembly accuracy</p><p> </p><p>There is more information in this Wikipedia article:</p><p> </p><p><a href="http://en.wikipedia.org/wiki/Acme_thread_form" target="_blank">Trapezoidal thread forms - Wikipedia, the free encyclopedia</a></p><p> </p><p> </p><p>You bring up a good question about clamping force. While these usually will not back drive, a unified thread is probably better in this area for clamping.</p><p> </p><p>Interestingly, the Mark V action with the "9 lugs" looks a great deal like a trapezoidal (stub acme) thread with 3 horizontal slots cut into it.</p><p> </p><p>As a practical matter, I wonder if the equipment that most smiths have is capable of producing a self centering stub acme thread on a barrel ? I am tempted to build up a rifle with this setup as a fun test.</p></blockquote><p></p>
[QUOTE="HarryN, post: 980370, member: 69773"] Thanks for the reply. I could be wrong, but I think it would only make sense to make the thread stub acme if this was the plan for both parts (action and barrel) from the beginning, not as a re-thread. The typical reasons that acme / stub acme type threads are used are: - The root of the acme thread is wider, so the individual threads are stronger. On a stub acme, this is even more the case. - The traditional threads tend to have sharp / narrow edges, which can become stress concentrators. If there is plenty of material it probably does not matter, but if the barrel / action area is getting thinner, this might be a factor. - Acme are often made to be self centering, which can increase assembly accuracy There is more information in this Wikipedia article: [url=http://en.wikipedia.org/wiki/Acme_thread_form]Trapezoidal thread forms - Wikipedia, the free encyclopedia[/url] You bring up a good question about clamping force. While these usually will not back drive, a unified thread is probably better in this area for clamping. Interestingly, the Mark V action with the "9 lugs" looks a great deal like a trapezoidal (stub acme) thread with 3 horizontal slots cut into it. As a practical matter, I wonder if the equipment that most smiths have is capable of producing a self centering stub acme thread on a barrel ? I am tempted to build up a rifle with this setup as a fun test. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Gunsmithing
Stub acme thread for barrel / action mounting
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