Argon, Nitrogen and Helium Cylinder Thread Chart
The same argon fills cylinders in Houston, Hamburg and Leeds behind three different threads — 0.965"-14 NGO, W 21.8 × 1/14 and 5/8" BSP — and German nitrogen has a fourth, W 24.32 × 1/14. A regulator bought in one country, a cylinder rented in another or a welder shipped with the wrong inlet nut ends at the same question: which thread is this, and what joins it to the other one. EKINSUN LTD is a custom parts manufacturer that machines the adapter between two inert-gas connections, or from one of them to an NPT, BSPP or metric port, from 1 piece.
| Connection | Thread | Gases / where | Pressure | Mates with |
|---|---|---|---|---|
| CGA 580 | 0.965"-14 NGO, right-hand, internal (female) in the valve | Argon, nitrogen, helium, neon, krypton, xenon and argon / CO₂ welding mixes — USA and Canada | Up to 3,000 psig | Regulator nut 0.960"-14 NGO male with a nipple that seats inside the valve |
| CGA 680 | 1.045"-14 NGO, right-hand, internal | Argon, nitrogen and helium in cylinders filled above 3,000 psig — USA | 3,001–5,500 psig | A regulator built for CGA 680 and 5,500 psig; not adapted down to CGA 580 |
| CGA 677 | 1.030"-14 NGO, left-hand, external | Argon and nitrogen in 6,000 psig cylinders — USA | 6,000 psig class | A regulator built for CGA 677; left-hand here does not mean a flammable gas |
| DIN 477 No. 6 — W 21.8 × 1/14 | 21.8 mm, 14 TPI, Whitworth form, right-hand, male on the valve | Argon, helium, CO₂, neon, krypton, xenon and argon mixes — Germany and much of the EU | 200 bar cylinders | Female W 21.8 × 1/14 regulator nut with a flat seal |
| DIN 477 No. 10 — W 24.32 × 1/14 | 24.32 mm, 14 TPI, Whitworth form, right-hand, male on the valve | Nitrogen — Germany; a nitrogen regulator does not fit an argon cylinder there | 200 bar cylinders | Female W 24.32 × 1/14 nut |
| W 30 × 2 (DIN 477 300-bar series) | 30 mm, 2 mm pitch, with a different seat geometry per gas group | Argon, nitrogen, helium and other non-flammable gases filled to 300 bar — Germany | 300 bar cylinders | A 300-bar regulator; not adapted to a 200-bar connection |
| BS 341 No. 3 — 5/8" BSP | 5/8" BSP (G 5/8, 22.91 mm, 14 TPI), right-hand, female cone in the valve | Argon, argon / CO₂ mixes, nitrogen, helium and air — and oxygen — UK and Ireland | Around 230 bar; 300-bar cylinders use ISO 5145 connections | Regulator bullnose with a 5/8" BSP right-hand nut |
| G 5/8 right-hand (China) | G 5/8, 14 TPI, male on the valve, female nut on the regulator | Argon, nitrogen and oxygen regulators built for the Chinese market | Cylinder rating as marked | Female G 5/8 regulator nut; measure before ordering — seats vary by maker |
Cylinder on one side, regulator on the other? Name both connections (or the country and the gas), the material and the quantity. Common brass pairs may be on our shelf; an unusual pair or a stainless one is machined from a single piece, and the unit price drops at 50 and at 500 pieces. Price back within 12 hours.
Designations per CGA V-1, DIN 477 and BS 341, with gas-supplier cylinder data sheets; 1 in = 25.4 mm. Pressure classes: CGA 580 up to 3,000 psig, CGA 680 from 3,001 to 5,500 psig, German and UK standard cylinders 200–230 bar, 300-bar cylinders on their own connections. Regulators made in China are not covered by one standard: check the nut with a gauge or send a photo beside a rule.
Oxygen and Fuel-Gas Connections — Recognise Them, Do Not Cross Them
Oxygen sits on CGA 540 in the US and G 3/4 in Germany, and the flammable gases on left-hand threads, so that a regulator from another gas cannot go on by mistake. A left-hand cylinder thread marks a flammable gas, with one inert exception: CGA 677 on 6,000 psig argon and nitrogen cylinders. We do not machine adapters to or from the connections below.
| Connection | Thread | Gas / where |
|---|---|---|
| CGA 540 | 0.903"-14 NGO, right-hand, external | Oxygen — USA |
| DIN 477 No. 9 | G 3/4, right-hand | Oxygen — Germany |
| CGA 510 | 0.885"-14 NGO, left-hand, internal | Acetylene, propane, butane — USA |
| CGA 350 | 0.825"-14 NGO, left-hand, external | Hydrogen, methane — USA |
| DIN 477 No. 1 | W 21.8 × 1/14, left-hand | Hydrogen, methane, propane — Germany |
| BS 341 No. 4 | 5/8" BSP, left-hand | Acetylene, hydrogen, propane and fuel mixes — UK |
CGA 580, CGA 680, W 21.8 and G 5/8 Thread Sizes
What is the CGA 580 thread size?
CGA 580 is a 0.965"-14 NGO right-hand internal thread in the cylinder valve (24.51 mm, 14 TPI); the regulator nut is 0.960"-14 NGO male, and the connection is rated to 3,000 psig for argon, nitrogen, helium and argon / CO₂ mixes.
What is the CGA 680 thread size?
CGA 680 is a 1.045"-14 NGO right-hand internal thread (26.54 mm) on US argon, nitrogen and helium cylinders filled from 3,001 to 5,500 psig; a CGA 580 regulator nut does not enter it.
What size is the W 21.8 × 1/14 cylinder thread?
W 21.8 × 1/14 is 21.80 mm across the crests with 14 threads per inch (1.814 mm pitch), Whitworth 55° form, right-hand, male on German and EU argon, helium and CO₂ cylinder valves to DIN 477 No. 6 at 200 bar.
What thread is a G 5/8 regulator nut?
G 5/8 is a 22.91 mm, 14 TPI Whitworth parallel thread (ISO 228); argon, nitrogen and oxygen regulators built for the Chinese market carry it as a right-hand female nut, and UK cylinder valves carry it as a female 5/8" BSP outlet (BS 341 No. 3).
Five Connections Between 21 and 25 mm, All 14 Threads per Inch
A pitch gauge does not separate these five: every one is 14 TPI. Measure the outside diameter of the male thread (or the bore of the female), look at the crests — sharp-topped 60° NGO or rounded 55° Whitworth — and note whether the cylinder valve carries the male or the female half. CGA 580 and W 24.32 are 0.19 mm apart in diameter; the form and the gender settle it.
| Connection | Major diameter | Pitch | Form | Gender on the cylinder valve |
|---|---|---|---|---|
| CGA 320 (CO₂, USA) | 0.825" = 20.96 mm | 14 TPI (1.814 mm) | NGO 60° | Male |
| W 21.8 × 1/14 (argon, EU) | 21.80 mm | 14 TPI (1.814 mm) | Whitworth 55° | Male |
| G 5/8 / BS 341 No. 3 (UK, China) | 22.91 mm | 14 TPI (1.814 mm) | Whitworth 55° | Female in UK valves; male on Chinese-market valves |
| W 24.32 × 1/14 (nitrogen, Germany) | 24.32 mm | 14 TPI (1.814 mm) | Whitworth 55° | Male |
| CGA 580 (argon, nitrogen, USA) | 0.965" = 24.51 mm | 14 TPI (1.814 mm) | NGO 60° | Female |
Inert-Gas Cylinder Adapters We Machine
Shelf adapters cover the common pairs, such as CGA 580 to CGA 320, in brass. When the pair is unusual, the material has to be stainless, the far end is a port instead of a regulator, or the adapter ships inside your product, it is machined: each thread cut to its own gauge, the seat to the regulator it meets, the bore to your flow.
| Product | Cylinder end | Regulator or port end | Material, rating | Used for |
|---|---|---|---|---|
| CGA 580 × CGA 320 adapter | CGA 580 nut, 0.960"-14 NGO right-hand male, with nipple | CGA 320 male, 0.825"-14 NGO right-hand, flat washer face | Brass CW614N or 316L; 3,000 psig | A CO₂ regulator on an argon, nitrogen or argon / CO₂ cylinder (MIG welding, nitro coffee, purging); the regulator must be rated for the cylinder |
| CGA 320 × CGA 580 adapter | CGA 320 nut, 0.825"-14 NGO right-hand female, nipple and washer | CGA 580 port, 0.965"-14 NGO right-hand female | Brass CW614N or 316L; 3,000 psig | An argon or nitrogen regulator on a CO₂ cylinder |
| CGA 580 × NPT adapter | CGA 580 nut, 0.960"-14 NGO right-hand male, with nipple | 1/4"-18 or 1/2"-14 NPT, male or female; straight or 90° | Brass CW614N or 316L; 3,000 psig | A cylinder straight into a manifold, purge line, test rig or analyser inlet |
| CGA 580 × W 21.8 × 1/14 adapter | CGA 580 nut, 0.960"-14 NGO male (US cylinder) | W 21.8 × 1/14 right-hand male, 21.80 mm, flat seal face (EU regulator nut) | Brass CW614N or 316L; 200 bar | A US cylinder on a German or EU argon regulator; the reverse pair has the genders swapped |
| W 21.8 × 1/14 × G 5/8 adapter | W 21.8 × 1/14 right-hand female nut (EU cylinder valve) | G 5/8 right-hand, 22.91 mm × 14 TPI: male for a Chinese-market nut, female for a UK bullnose | Brass CW614N or 316L; 200 bar | A UK or Chinese-market argon regulator on an EU cylinder |
| W 24.32 × 1/14 × W 21.8 × 1/14 adapter | W 24.32 × 1/14 right-hand female nut, 24.32 mm (German nitrogen valve) | W 21.8 × 1/14 right-hand male, 21.80 mm | Brass CW614N or stainless; 200 bar; flat seals both ends | A German nitrogen cylinder on an argon regulator rated for 200 bar nitrogen |
| Straight hex coupler | Female, any cylinder or regulator thread in the chart | Female, the same thread or a second one | Brass CW614N or 316L; length and hex across flats to order | Extending a cylinder connection or joining two male ends |
| Cylinder pigtail | Cylinder nut: CGA 580, W 21.8 × 1/14, W 24.32 × 1/14 or G 5/8 | Manifold nut or 1/4"-18 NPT male | Copper or 316L tube; length to your cylinder rack | A cylinder to a manifold through a flexible line |
Every product in the table is machined in brass CW614N as standard, or in 316L (1.4404) or 304 (1.4301) from certified bar with an EN 10204 3.1 certificate for laboratory, analyser and food-grade nitrogen lines. An adapter that ships with your welder, dispenser or analyser repeats from one approved drawing in batches of 50 to 500, and the unit price falls as the quantity rises.
Price for one of these pairs: tap its row, or send the two ends and the gas. Brass CW614N or 316L; drawing to approve before machining; from 1 piece.
CO₂-only threads (TR21-4, CGA 320, paintball and cartridge threads) are on CO₂ cylinder thread adapters; left-hand threads outside gas cylinders are on left-hand thread adapters; the NPT and BSPP port end is explained on the fitting thread identification chart.
Pressure, Seats and the Adapters We Do Not Make
CGA 580 is rated to 3,000 psig, and an adapter changes the thread, not the rating of anything attached to it. US cylinders filled above that carry CGA 680 or CGA 677 so that a 3,000 psig regulator cannot be fitted; a step-down adapter would undo that, so we do not make one, and the same goes for 300-bar cylinders in Europe. A CO₂ regulator on argon or nitrogen must be rated for the full cylinder pressure — around 2,000 psig or more in a US cylinder and 200 bar in a European one, against about 830 psi in a CO₂ cylinder. The wall each bore needs at 3,000 psig or 200 bar is on the thread adapter strength chart, and the 90° form of any pair on threaded elbows. Each seat is machined to its standard, with the washer face where the connection uses a washer (CGA 320) and the nipple seat where it seals inside the valve (CGA 580). In the UK, argon and oxygen share 5/8" BSP right-hand: an adapter made for argon stays on inert gas.
Bought From Stock or Machined to Order
The brass CGA 580 to CGA 320 adapter is a catalogue part, and we supply standard pairs too. A 316L version, a port end, an unusual pair or a reorder of 500 is machined; a pressure step-down or an oxygen cross is refused.
| Your need | Sold off the shelf? | Our answer |
|---|---|---|
| A brass CGA 580 to CGA 320 adapter, one piece, today | Yes — welding-gas and home-brew suppliers | Buy it from stock at a welding-gas or home-brew supplier, or ask us — we may have it in stock, and the more pieces, the lower the unit price; for one piece today, a local supplier is faster. |
| The same pair in 316L with a material certificate | No | Machined from certified 316L bar from 1 piece, EN 10204 3.1 certificate included. |
| A cylinder connection on one end and NPT, BSPP or a metric port on the other | Rarely | Made to order: the cylinder end to its standard, the port to yours, straight or 90°. |
| Two inert-gas standards no kit pairs — W 24.32 to CGA 580, G 5/8 to W 21.8 in stainless | No | Both ends cut to gauge from 1 piece; send the regulator, or a photo of the nut beside a rule. |
| A CGA 680, CGA 677 or 300-bar cylinder onto a 3,000 psig or 200-bar regulator | No — and it should not exist | We do not make it: the step-down puts a lower-rated part on a higher-pressure cylinder. Use a regulator built for that connection. |
| An oxygen or left-hand fuel-gas cylinder onto a regulator for another gas | No | We do not make oxygen or flammable-gas cross adapters; those connections differ on purpose. |
| A regulator, flowmeter or cylinder valve | Yes — gas-equipment suppliers | Not what we make: we machine the adapter body; regulators and valves come from their certified makers. |
What We Need to Quote an Inert-Gas Adapter
The cylinder connection by name, or the country and gas if the valve is unmarked; the regulator or port connection with its gender; the gas and pressure (standard, 300 bar or CGA 680 class); brass or stainless and any certificate; straight or 90°; the quantity now and on reorder. A photo of the cylinder valve and the regulator nut next to a rule is enough to identify an unmarked thread. We answer within 12 hours with a price and a dimensioned drawing, and machine from 1 piece after you approve it.
Argon and Nitrogen Cylinder Thread FAQ
It depends on the country. US and Canadian argon cylinders use CGA 580 (0.965"-14 NGO, right-hand, internal) up to 3,000 psig and CGA 680 above that; German and most EU cylinders use W 21.8 × 1/14 to DIN 477 No. 6; UK and Irish cylinders use a 5/8" BSP right-hand female connection (BS 341 No. 3). Regulators built for the Chinese market usually carry a G 5/8 right-hand nut.
A CGA 580 to CGA 320 adapter makes the threads meet, and the connection is rated 3,000 psig. The regulator is the limit: an argon or nitrogen cylinder is filled to around 2,000 psig or more in the US and 200 bar in Europe, against about 830 psi in a CO₂ cylinder, so the regulator inlet and gauge must be rated for the full cylinder pressure. The adapter does not change that.
No. CGA 580 is 0.965 inch (24.51 mm), 14 TPI, 60° NGO form and female in the valve; W 24.32 × 1/14 (DIN 477 No. 10, German nitrogen) is 24.32 mm, 14 TPI, 55° Whitworth form and male on the valve. The pitch is the same and the diameters differ by 0.19 mm, so only the form and the gender tell them apart.
W 24.32 × 1/14 right-hand, DIN 477 No. 10. It is larger than the W 21.8 × 1/14 used for argon, helium and CO₂ (No. 6), so a German argon regulator does not fit a nitrogen cylinder without an adapter, and the regulator must be rated for nitrogen at 200 bar.
No. Oxygen (CGA 540, DIN 477 No. 9, G 3/4) and the left-hand fuel-gas connections (CGA 510, CGA 350, DIN 477 No. 1, BS 341 No. 4) are kept apart from other gases on purpose, and we do not machine adapters that cross them. The same applies to stepping a CGA 680, CGA 677 or 300-bar cylinder down to a lower-rated regulator.
EKINSUN — a custom parts manufacturer that machines inert-gas cylinder adapters (CGA 580, CGA 320, W 21.8 × 1/14, W 24.32 × 1/14, G 5/8 / BS 341 No. 3) to each other or to NPT, BSPP and metric ports, in brass CW614N or 316L stainless, from 1 piece; common brass pairs may be in stock. Send both ends, the gas and the quantity; quote in 12 hours.