Brazing nozzle sizes explained

The number on a brazing nozzle is a code for orifice diameter and gas flow — not a physical length. A bigger number means a wider orifice and more heat at the joint. Because the number is standard across the British No. series, you can order a replacement without measuring anything: match the stamp, confirm the seat, done.

British-style brazing nozzles run up the No. series from light work to heavy. As a working guide: No. 8 for light silver brazing and small-bore tube, No. 10 for small fittings and general light brazing, No. 13 for general copper/brass/steel brazing up to medium section, No. 16 for heavier joints and light pre-heat, and No. 20–25 for heavy section and substantial pre-heat.

Note that the brazing series is separate from the acetylene welding No. 1–25 series — the two are sized and shaped differently.

The rule of thumb: fit the smallest nozzle that flows the joint in good time — it gives the cleanest result and wastes the least gas. For a 15–22 mm copper or brass joint, No. 10 is the everyday answer; drop to No. 8 for delicate work and step up when the joint is slow to flow.

A brazing nozzle throws a softer, wider flame envelope so the filler flows into the joint without melting the base metal. A welding nozzle concentrates heat for fusion welding. Different gas set-ups also matter: oxy-acetylene and oxy-propane use different size equivalents ⚠, so always read the product table for your gas.

Read the stamp on your old nozzle, then check the seat and thread against your torch head ⚠. For the bench, the 3-size set covers most work; if you know your staple size, buy the single — No. 10 is the most re-ordered brazing size for a reason. Not sure? Send us your torch model and we will match it.

Clean carbon off regularly with a tip cleaner set, and replace a nozzle when the orifice is oval or the flame splits — a worn brazing nozzle wastes gas and makes joints slowly, no matter how well it is cleaned.