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3/4" NPT (m) to 1" G (f)

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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3/4" NPT (m) to 1" G (f)

Unread postAuthor: PVC Arsenal 17 » Thu Oct 11, 2012 12:39 pm

As the title says, I need to connect something with male 3/4" NPT threads to something that has female 1" G threads. A direct adapter does not exist (afaik), so what other options exist that would minimize dead space?

Tapping a 1" G plug maybe?

Or will a male 1" G to female 1" NPT adapter plus a reducer bushing not actually create significant dead space?

G thread = BSPP thread

Thanks...


It's a massive Euro-style QEV with 1" G threads all around, plus a massive 3/4" NPT slide valve.... I'm making a piece-together big bore pneumatic (minimal machining is a requirement).
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Last edited by PVC Arsenal 17 on Wed Oct 31, 2012 9:06 pm, edited 4 times in total.

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Unread postAuthor: PVC Arsenal 17 » Wed Oct 31, 2012 9:02 pm

bump re-purposed thread
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 01, 2012 1:10 am

Tapping a 1" G plug maybe?


That's probably what I would go for.
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Unread postAuthor: dewey-1 » Thu Nov 01, 2012 7:26 am

Here is the minmal machining method that is probably cheaper unless you already have a 3/4 NPT tap and correct drill size.

As jsr mentioned the tapped plug is better as can be seen in this picture.
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Unread postAuthor: PVC Arsenal 17 » Thu Nov 01, 2012 12:53 pm

Thanks for the pictures, Dewey! I do have a 3/4" NPT tap but I'll need to find a 59/64" drill bit.

I'm concerned about making a centered hole using my whacky drill press. Would you advise drilling from the hollow end, or drilling from the closed end using progressively larger bits?
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Unread postAuthor: dewey-1 » Thu Nov 01, 2012 5:15 pm

PVC Arsenal 17 wrote:Thanks for the pictures, Dewey! I do have a 3/4" NPT tap but I'll need to find a 59/64" drill bit.

I'm concerned about making a centered hole using my whacky drill press. Would you advise drilling from the hollow end, or drilling from the closed end using progressively larger bits?


You could also use a 15/16" drill.
Get a a cheap Harbor Freight machinist (drill press) vise. Well worth it!
Center punch accurately on the flat of the hex side.
Start with 3/16" as a pilot and progressively enlarge. Use oil to keep drill bit cool and aid drilling.
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Unread postAuthor: PVC Arsenal 17 » Thu Nov 01, 2012 5:32 pm

Much appreciated, Dewey. While I'm at it I'll pick up a cheapo belt sander for my knife sharpening needs.
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Unread postAuthor: dewey-1 » Thu Nov 01, 2012 5:56 pm

Home Depot has a 4" vise that is cheap.
It appears Harbor Freight has quit stocking the drill press vises.
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Unread postAuthor: PVC Arsenal 17 » Mon Nov 05, 2012 1:57 pm

Well here they are:

Image

Undoubtedly BSPP threads, not NPT. But, NPT male threads into them no problem. In fact since it's a straight thread, the additional insertable depth almost makes it seem more secure than the typical NPT-NPT connection which offers less engagement.

It doesn't seem like blow-out would be likely. If anything goes wrong it would probably be leakage. I'm tempted to go ahead without adapters and just use a ton of pipe dope and teflon tape.

If anyone thinks I'm a candidate for a Darwin award, I'll happily sell them for $35 shipped to the lower 48.
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Unread postAuthor: Petitlu » Mon Nov 05, 2012 2:19 pm

J'achète ! ;)
Tu envoie en France ?
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2012 4:41 pm

hehe please sell them to Petitlu, I'm sure he'll put them to some insane but ultimately entertaining use :D
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Unread postAuthor: Petitlu » Mon Nov 05, 2012 4:47 pm

Thank you!
Yes madman's machine, necessarily!

In the fact Jack, I did not forget the test Neverlost! :wink:
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 05, 2012 4:49 pm

Petitlu wrote:In the fact Jack, I did not forget the test Neverlost! :wink:


haha I almost forgot about it myself :) so... you haven't lost it yet :D
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Unread postAuthor: Petitlu » Mon Nov 05, 2012 4:53 pm

I had family problems for a moment but now I can make the test!
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 06, 2012 12:37 am

Petitlu wrote:I had family problems for a moment but now I can make the test!


Sorry to hear that, hope it was not related to unexpected loud noises from the garden! Great to see you back and looking forward to some cool stuf :)

I digress, apologies to PVC for the hijack.
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