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Author Topic: Newbie air tube threading question  (Read 461 times))

Offline Bugman

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Newbie air tube threading question
« on: June 26, 2021, 11:16:31 AM »
Hi all: I've commissioned a HPA adapter, drop block made of aluminum and intend to have it threaded to install directly on the existing 13/16-28 thread Prod air tube. I have two different blocks on order just to see which I prefer. The first is a reverse block (ninja regulated around 1400psi and bottle facing towards the trigger group) described above and using the stock air tube to receive the block (with two orings up from I believe as per best practices). The second is a forward mounted version with the ninja and bottle facing away from the shooter, but I would have to consider shortening the tube. Again most mods appear to pin the block rather than threading so thus the question.

My question is: Should a newbie consider threading his own air tube on a stock Prod air tube as I would prefer to cut the tube on a forward mounted bottle? Most of the discussions here are different types of materials and threading, but if I'm using a stock tube with known, compatible threading is that a big deal to do on your own? I'm more of a wood worder than metal working, but I know tools...

Thoughts?
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Offline BigBird

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Re: Newbie air tube threading question
« Reply #1 on: June 26, 2021, 12:01:04 PM »
You said you are having the part commissioned?  Are you having it made to max diameter then you do the threading?  Are you single pointing on a lathe or with dies?  Do you have a hydraulic hand pump to test it once complete?  Pinning is a different operation.  Depending on how you do it it is usually stronger but you can mess it up just as easily.
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Offline rsterne

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Re: Newbie air tube threading question
« Reply #2 on: June 26, 2021, 01:04:59 PM »
I would have the block threaded by your manufacturer.... You can check the threads by threading it into a factory 2260 tube.... Then boring out the shortened tube and tapping it with a 13/16-28 tap should give you perfect threads.... I would personally not be comfortable doing internal single point threading of such a fine pitch, as it is very difficult to hold the required tolerances, unless you have lots of experience.... A tap, as long as it is held straight with the tube.... and providing the tube is bored to the correct size for threading with your required thread.... is a LOT easier, and should always end up within tolerance.... JMO....

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Offline Bugman

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Re: Newbie air tube threading question
« Reply #3 on: June 26, 2021, 03:27:57 PM »
I would have the block threaded by your manufacturer.... You can check the threads by threading it into a factory 2260 tube.... Then boring out the shortened tube and tapping it with a 13/16-28 tap should give you perfect threads.... I would personally not be comfortable doing internal single point threading of such a fine pitch, as it is very difficult to hold the required tolerances, unless you have lots of experience.... A tap, as long as it is held straight with the tube.... and providing the tube is bored to the correct size for threading with your required thread.... is a LOT easier, and should always end up within tolerance.... JMO....

Bob
Yes, the block will be threaded by the machinist, and he has a disco tube to test it on (same as Prod I believe). The other option is to wait for Don Cochran to free up some time ;)
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Offline luge007

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Re: Newbie air tube threading question
« Reply #4 on: September 12, 2021, 08:21:09 AM »
Bugman,
So, how did it turn out??  I found this thread a bit late, but I was going to recommend sending the actual tube (prod) to your machinist to match threads to.  NOT sure if it matters, but give how precise the airtube threads need to be and how much is at stake @ 2k-3k psi, the better the fit, the safer the result.



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Offline HunterWhite

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Re: Newbie air tube threading question
« Reply #5 on: September 12, 2021, 01:18:35 PM »
May I ask what machinist you have contracted?
I too would like to get a tube cut down. The only machinist that I'm certain has the knowledge of stress factors of the threads under pressure is Dyotat100 ( Doug) but I  don't think that he is still a member here.
I tried the order from Crosman custom shop, but they don't actually build custom stuff except assembly of guns from stock parts.

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Offline mobilehomer

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Re: Newbie air tube threading question
« Reply #6 on: September 12, 2021, 08:16:25 PM »
May I ask what machinist you have contracted?
I too would like to get a tube cut down. The only machinist that I'm certain has the knowledge of stress factors of the threads under pressure is Dyotat100 ( Doug) but I  don't think that he is still a member here.
I tried the order from Crosman custom shop, but they don't actually build custom stuff except assembly of guns from stock parts.

Hunter

He is still a member. Active today.
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