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JB Threads

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JB Threads

Unread postAuthor: shud_b_rite » Tue Mar 13, 2007 11:25 pm

For me the hardest thing about making a pneumatic gun is matching threads up. Some things use 3/8 " others use 1/2 " or 1/4 ", some are BSP, NPT and all different kinds.

My theory is that if I have a female or male thread and I want to adapt it to a different type, I can just place the 2 threads together as shown in the diagram, wrap them in some kind of non stick stuff and then cover it all in JB weld and let it set. When it is set, I can unscrew the threads and use a file to make the outside into a square so it can be easily tightened with a spanner.

I know it wont be perfect (it will probably look like crap) and I wouldn't take it to extreme pressures but its a quick solution for someone who doesn't have any means of welding. The only thing I'm not sure about is what to use to prevent the JB weld from being permanently stuck to the threads, preventing me from unscrewing it.

What do you reckon, will it work? What can I use in between the threads?



Edit:

Ok I made it the other day. I decided that It would be easier and better if the JB weld was fixed in place, so I cant unscrew the threads.

I modified a pin valve on a paintball tank to allow more flow and I JB welded it to a 1/4 inch coupler which then screws into a air compressor quick connect fitting. So now I have a paintball tank as a chamber. Now all I have to do if make a barrel and trigger system for a gun.
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Attachments
JB thread.jpg
JB thread.jpg (39.39 KiB) Viewed 1167 times
whole.jpg
This is my modified pb tank complete with quick connect fittings.
valve tank.jpg
This is the pin valve and PB tank I modified that is JB welded to the quick connect fitting
Last edited by shud_b_rite on Fri Mar 16, 2007 6:10 pm, edited 1 time in total.
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Unread postAuthor: A-98 » Wed Mar 14, 2007 12:05 am

how are you going to create and air passage?

tho it seems like a good idea, it seems a bit hard to implement. i would suggest using a slower setting epoxy (not JB quik)so that when it is semi hard you could unscrew it., maybe. or use petroleum jelly as a non-stick thing.
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Unread postAuthor: shud_b_rite » Wed Mar 14, 2007 12:16 am

Oh sorry I forgot to mention. I will drill a hole through it for an air passage. I will try it out on Friday or Saturday and I will put up some pictures. I will also have to make sure that the JB weld is pressed in really hard so it fills all the threads.
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Unread postAuthor: Pete Zaria » Wed Mar 14, 2007 1:23 am

It should work, but you should put the fittings much closer together than you show them in that diagram. In fact, I think you could safely have them touching...

Make sure you mix the JBweld properly, cover the fittings in nonstick spray, cover the fittings in JBweld the way you want, let it cure for a day, then shape it. Don't overwork it while shaping it, just make the sides flat enough to get a good grip on with a big pair of pliers. I think it would safely hold at least 125 or 150psi. I've heard of people using JBweld in very high-pressure applications with no disastrous results.

Good luck.

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Pete Zaria.
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Unread postAuthor: frankrede » Wed Mar 14, 2007 6:41 am

It would come out better using a tap. I'm sur ethe fitting would hold but you would have to be careful.
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Unread postAuthor: Hotwired » Wed Mar 14, 2007 10:54 am

I reckon you'd be better off getting a 3/8 to 1/4 adapter than making one out of epoxy.

You can buy them in f/f or m/f or m/m form.
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Unread postAuthor: itwentboom » Wed Mar 14, 2007 7:15 pm

Dude are you for real? No way can you do that.
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Unread postAuthor: Pete Zaria » Wed Mar 14, 2007 7:16 pm

itwentboom wrote:Dude are you for real? No way can you do that.


I think you underestimate JBweld... :)

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Unread postAuthor: itwentboom » Wed Mar 14, 2007 7:26 pm

I would build something that works. Why take a chance that would be so Ghetto looking as well. I would not encourage that at all.
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Unread postAuthor: deusXmachina » Wed Mar 14, 2007 7:30 pm

Ehhh...I love JB weld as much as the next guy. But I've had it fail in my face. It's excellent when used properly (filling gaps between various bits of pipe) but dangerous if you don't use enough/ mix it right/ put it in the wrong place. I had a water balloon ballista and the winch pin (3/8" eye bolt) was JB welded to another eye hook on the elastics. Second time I fired it, the eye bolt shot straight back at me.

I personally would not trust two threaded ends wrapped with JB, no matter how much was used, especially if you're going to be wrenching it. I'd tap it, but if that isn't convenient, find pieces that fit roughly together and stick them together with JB in the joint, like if you were to solvent weld the PVC. JB works a lot better for filling the circular space between fittings than it does as rudimentary casting material.
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Unread postAuthor: Fnord » Wed Mar 14, 2007 7:33 pm

Put the jbweld in a short section of pvc pipe and use the same techniques, it wont look ghetto at all, and it will be stronger
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Unread postAuthor: itwentboom » Wed Mar 14, 2007 11:02 pm

IT will look Ghetto but whatever. I was thinking of using clay for my next combustion because thats all I have around my house LOL.
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Unread postAuthor: frankrede » Wed Mar 14, 2007 11:27 pm

why not machine it using pvc stock?
Drill a hole smaller than the threads are heat the pvc slightly and thread it into the hole.
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Unread postAuthor: shud_b_rite » Fri Mar 16, 2007 6:13 pm

Have a look at my first post and you will see my completed product. It doesnt look as ghetto as I thought. It feels pretty sturdy, the max I would take it up to is probably 250psi. After a few trials I may decide to sleeve it with something for safety.
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Unread postAuthor: itwentboom » Fri Mar 16, 2007 9:04 pm

Dude that is a Ghetto way of doing stuff. I would love to see a pic of that so i can laugh all night. I would even use that as wallpaper on my desktop LOL. You should called it the Gh.etto Shooter.
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