Too little gas is porosity; too much is turbulence that pulls in shop air — which is also porosity. Here are the flow ranges that actually work, plus a CFH↔L/min converter for foreign meters.
| Cup Size | CFH | L/min | Use For |
|---|---|---|---|
| #4–#5 | 10–15 | 4.7–7.1 | Fine work, thin sheet |
| #6–#7 | 15–20 | 7.1–9.4 | General DC steel/stainless |
| #8–#10 | 20–25 | 9.4–11.8 | Heavier sections, AC aluminum |
| #12+ | 25–35 | 11.8–16.5 | Big cups, high heat |
Cup size drives the flow, not the other way around. A #4 cup at 25 CFH is useless — the gas turns into a vortex.
| Wire | CFH | L/min | Thickness |
|---|---|---|---|
| 0.023" | 15–20 | 7.1–9.4 | 24–20 ga, short-circuit |
| 0.030" | 20–25 | 9.4–11.8 | 1/16"–1/8", short-circuit |
| 0.035" | 25–30 | 11.8–14.2 | 1/8"–3/16" |
| 0.045" | 30–40 | 14.2–18.9 | 1/4"–3/8" |
| 1/16" | 35–45 | 16.5–21.2 | 3/8"+ spray |
For 100% CO2 you can drop 5–10 CFH — it's denser and hugs the arc better. Spray transfer at high amps lives at the top of the range.
European and Asian regulators read liters per minute; US bottles read cubic feet per hour. 1 CFH = 0.4719 L/min. Type in either box.
| CFH | L/min | Where It Shows Up |
|---|---|---|
| 10 | 4.7 | Fine TIG, #4 cup |
| 15 | 7.1 | General TIG |
| 20 | 9.4 | TIG on steel / thin MIG |
| 25 | 11.8 | 0.035" MIG |
| 30 | 14.2 | 0.045" MIG |
| 35 | 16.5 | Heavy MIG / spray |
| 40 | 18.9 | 1/16" MIG / spray |
| 45 | 21.2 | Top-end spray |
Above ~5 mph (8 km/h), bump flow 25% or rig a screen. Above 10 mph, switch to flux-cored or put the part inside.
Flow meters are calibrated for a specific gas and density. Don't trust a CO2 meter's reading for argon — use the correct one.
TIG tungsten oxidizes the second the post-flow ends. Set 5–10 seconds on thin stainless or when using small tungsten.
Use your calculated requirements to get an equipment recommendation for your application.
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