Gas Cutting Nozzles FAQs
Straight answers to the questions people ask most when choosing and using gas cutting nozzles.
How do I choose the right cutting nozzle size?
Cutting nozzles are sized for the thickness of steel you cut. The nozzle size sets how much oxygen and fuel gas flows, so a bigger nozzle suits thicker plate and a smaller one suits thin sheet. Each maker publishes a chart relating nozzle size to thickness and giving the oxygen and fuel gas pressures to use, and you should work from the chart for your own nozzle type.
A nozzle that is too large wastes gas and gives a wide, rough cut, and one that is too small cannot cut cleanly through the plate. Choose for the thickness you cut most, and use a different nozzle for much thicker or thinner jobs.
Can I use the same nozzle on acetylene and on propane?
Not unless the maker says so. Nozzles are designed for a particular fuel gas, because the gases burn differently and need a different flame design and different amounts of oxygen. Propane and natural gas nozzles are not simply acetylene nozzles with different settings, and they have their own arrangement of preheat holes.
Using a nozzle with the wrong fuel gas gives a poor flame, slow preheating and a ragged cut, and can be unsafe. Choose a nozzle marked for the fuel gas you use, and check on the torch data plate and in its manual that the torch is designed for that gas too.
How do I clean a cutting nozzle?
Switch off the gases and let the nozzle cool, then clear the preheat holes and the central cutting oxygen bore with the correct size of tip cleaner. Push the cleaner straight in and out with a gentle action, use the cleaner sized for that hole, and do not force it. Never use drills, nails or wire, because they ruin the hole.
Finish by cleaning the outside and the sealing seat with a soft brush and removing any loose dirt. Ports blocked with slag cause a distorted flame, poor cuts and popping, so clean the nozzle whenever the flame looks uneven.
Why is my gas cut rough, or why is slag sticking to the underside?
Common causes are the wrong nozzle size for the plate, a worn or dirty nozzle, the wrong gas pressures, a travel speed that is too fast or too slow, and holding the nozzle too close to or too far from the plate. Rust, scale and paint on the plate can also upset the cut.
Clean the nozzle first, then check the pressures against the maker's chart and adjust your speed. Heavy slag on the underside often means you are moving too slowly or have too much heat, while sparks flying up from the top instead of through the plate usually mean the cut is not going right through, because you are moving too fast or using too little oxygen.