Posted: 11/17/2014 4:31:20 PM EDT
| Arfcom machinists, are you familiar with multiplying the major diameter of a shank by .995 for threading? |
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Usually .990. It does depend on the TPI, though. Finer threads get less reduction.
Five thousandths off an inch diameter isn't much. Bringing threads up to that sharp point serves no real purpose and you'll knock off that corner when you deburr them anyway. Plus it's that many fewer passes you have to make. The tougher the material, the further under the OD, or larger the tap drill, I use. |
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Quoted:
Shortest thread in arfcom history? 
I can't believe there's not at least one person to tell me I'm wrong.  I know, right? This sprouted from a discussion with the... gentleman... I work with that AR-10 thread shanks are not 1"-16 tpi, because the major diameter of the ones he's measured are .997"
I asked him if, when he cuts a 1.0625-16 tpi shank that is exactly 1.0625" with his full profile threading tool, does it take a scrape off the top of the threads on the last pass. Amazingly, it does. 
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Quoted:
I know, right? This sprouted from a discussion with the... gentleman... I work with that AR-10 thread shanks are not 1"-16 tpi, because the major diameter of the ones he's measured are .997"
I asked him if, when he cuts a 1.0625-16 tpi shank that is exactly 1.0625" with his full profile threading tool, does it take a scrape off the top of the threads on the last pass. Amazingly, it does. Quoted:
Quoted:
Shortest thread in arfcom history?
I can't believe there's not at least one person to tell me I'm wrong. I know, right? This sprouted from a discussion with the... gentleman... I work with that AR-10 thread shanks are not 1"-16 tpi, because the major diameter of the ones he's measured are .997"
I asked him if, when he cuts a 1.0625-16 tpi shank that is exactly 1.0625" with his full profile threading tool, does it take a scrape off the top of the threads on the last pass. Amazingly, it does. Is this the machinist version of a nerd thread? At least I understand what's going on more than in the IT threads. |
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Quoted:
I know, right? This sprouted from a discussion with the... gentleman... I work with that AR-10 thread shanks are not 1"-16 tpi, because the major diameter of the ones he's measured are .997"
I asked him if, when he cuts a 1.0625-16 tpi shank that is exactly 1.0625" with his full profile threading tool, does it take a scrape off the top of the threads on the last pass. Amazingly, it does. Quoted:
Quoted:
Shortest thread in arfcom history?
I can't believe there's not at least one person to tell me I'm wrong. I know, right? This sprouted from a discussion with the... gentleman... I work with that AR-10 thread shanks are not 1"-16 tpi, because the major diameter of the ones he's measured are .997"
I asked him if, when he cuts a 1.0625-16 tpi shank that is exactly 1.0625" with his full profile threading tool, does it take a scrape off the top of the threads on the last pass. Amazingly, it does. It's a misunderstanding of the defining features of the thread. The maj dia is a theoretical sharp point that doesn't need to physically be there to define the thread. The pitch diameter which is where the surface of the angled helix exists is the defining size of the thread. |