Small home made reusable refrigerant tank

straight taps need to seal on a gasket or O ring since that can not be done, just goop-ing on some type of sealant or silicone is not the correct way to make that seal.

I would use a valve that had a tapered pipe thread 1/4 to 3/8(depending on tank)on the inlet and drill appropriate hole size and tap with the matching size tapered pipe tap. Tapered pipe taps seal within the threads ,straight taps do not, (thats why the valve had a O-ring on it). you can put a wrap or two of Teflon tape or some pipe dope on the threads,either one just helps seal the thread to seal. just tighten and the seal is complete, no waiting for something to dry.

After you drill when using a npt tap you will need to use a reamer to taper the hole before you tap. That is the proper way to make a npt hole.

Why would you ream something if its going to be taperd after its tapped? unless your talking about some kind of taperd ream.

either way, after you tap be sure to hit the top and bottom edges of the threaded hole with a chamfer to deburr it and give it a nice clean bevel look. though i guess it would be impossible to chanfer inside the bottle.

also you'll get tap oil inside of the bottle, along with metal shavings. so you will need to flush the bottle with alcholo and then pull a vacuum on it to evaporate the remaining fumes.

Exahertz everything you said is wrong,you need to do some reading on taps & dies and how to make threads, you drill a straight hole and the pipe tap has the taper built into it, the same goes for a pipe die.

when drilling a hole that does not penetrate all the way thru the metal and is straight fine or course thread you need a 3 piece tap set(most come this way) starter tap, regular tap,and bottoming tap.



there are all kinds of threads,and ways to make seals , there's a whole book just on that and even that won't teach you what a good mechanic/machinist will.

how am i wrong? why would you ream (widen the opening of) your pilot hole before you tap it. what difference would it make with a taperd tap? you would just have to ingage the tap a little deeper. thus your NPT-male would have to screw in deeper to seat.

i've tapped with NPT BSP and Straights. and you tell me that nothing i said makes sense? so oil and metal shaving wolnt get into bottle, geeze! I want some of those taps! and let me guess, you dont clean up the top edge of the newly tapped hole? yea lets see how long that initial "starting lead" thread lasts when its only 1/1000 of an inch paper thick and sticking out at the top. i always chamfer my tapped holes, its a clean and durrable finishing touch, plus it helps guide the screw to ingage.

ok let me clarify

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That is the proper way

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Yes you should ream the hole first as the tap is supposed to cut threads only not take out material. If you use a npt tap without reaming you wont get the amount of threads that you would if you used a tapered ream. Understand? Do you want me to draw a picture?

turn the bottle upside down when taping, you can get away without using oil on soft metals like copper,brass aluminium,even mild steel as long as the tap size is small enough . Plus take its slow and keep reversing the tap to cut off the shavings. when to reverse depends on number of flutes on tap.

oil is always prefered,but tapping can be done without it. some metals used in aircraft that are cnc milled with no oil or solvent as in would dammage the metal.

a tapered ream. thats what i was wondering about. i guess it would make tapping an npt a lot easier/controllable depth, though i tap 1/4" npt in stainless using only a 7/16" drilled holes and they work quite nicely, they get a little harder after the first inch or so but the tap seems to manage.

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Originally Posted by wdrzal

turn the bottle upside down when taping, you can get away without using oil on soft metals like copper,brass aluminium,even mild steel as long as the tap size is small enough . Plus take its slow and keep reversing the tap to cut off the shavings. when to reverse depends on number of flutes on tap.

oil is always prefered,but tapping can be done without it. some metals used in aircraft that are cnc milled with no oil or solvent as in would dammage the metal.

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You can also fill the flutes with a bearing grease to catch the shavings.

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Originally Posted by 2long4u

You can also fill the flutes with a bearing grease to catch the shavings.

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:shrug: idk bout that one, maybe with harder metals as the shavings would be smaller and less likely to get between the teeth, but then again you might want bigger shavings for that like in softer metals :shrug:
good idea though and worthy of testing, i might just keep that in mind

Thats how we tap oil pans for a bigger drain plug when the customer strips it.

OK well i got my valve today from frosty freeze and i got out my tap and die set and i found that the die that fits on to the valve is a 1/2 20 NF so that means that the right tap for this valve is a 1/2 20 NF i can not find any taps that r UNF is there even such thing

I beleive that NF/UNF and NC/UNC are the same

ok thanks i think that UNF and UNC is in th USA and NF and NC r canada

The exact tap is 1/2*20 UNF Taper I use the one from: P&N Austria GH5 HSS.

Xeon where did u get that tap from

an industrial suply shop that was near my place.

someone said to put in a relief valve, but they have a built in relief valve, it is the hole next to the threaded torch connector thing, it is set to 300-400psi

xeon well i don't know what i did wrong but i got my tank all together and dry and i when't to pressure test it and when ever i put nitrogen then shut all the valves and took off the hose then hooked up my high side of my manifold to see if the tank had anything inside but there was nothing no psi's in small tank so i did again to test for leaks but there was none but again when i took off the hose and test to see how much psi's it had it had none what am i ding wrong please help

I have no idea, did you use a good quality Thread sealant that was rated for this type of service? I used: Permatex Thread sealant, it matched most of the requirements that it would need to withstand for this application, so far it is holding R-22 and R-134a with zero leaks or seepage ( I check the wait of the bottles every two days to watch for seepage, and so far been nearly a month and not even the slightest change in the weight!

know it is not leaking around the threads loses all psi's after i close the valve and take off the hose like the valve does not close how can i find out whether the valve works or not

How do you know it is not leaking around the threads?

put it under water and admit 100psi to it, and see where the bubles come from.

well when i put in 200 psi and soaped it all up and there was no bubbles but this was with my hose,regulator and tank still hooked up then i shut the valve on the small recovery tank and shut off my N2 and when i on hook my hose i lost all psi's in the tank i can open the valve back up and no n2 comes out could it be the valve (I did take out the pin and o-ring)

well did you tighten up the stem packing nut? or did you dismantle it to ensure the valve is clean?

yes i did but i will go back and try it again just to make sure