hi all, i remember some years ago a person i worked with telling me that once the cut is started you need only oxy to maintain it and can turn off the fuel. Ive been experimenting with this a bit at work lately as we have a bit of spare time. I've had mixed results.
The plate im working with varies from about 1/2" to 2". Im using an electric style plate cutting machine. There are all the usual adjustments for height, travel speed, etc. I start the cut as usual with a suitable tip and neutral flame, then once the cut is proceeding well i start to reduce the acetylene. Ive had some excellent results by reducing the acetylene to an extreme oxidising flame, to the point where the flame almost goes out. i reduce the travel speed a little at this point. The cuts im obtaining are really great - almost laser like. They are dead clean, with no slag at all and a very neat edge that doesnt need grinding. As a side benefit, there is less heat distortion on the cut, on full plate length cuts you can notice that the cut off section moves away from the main section by very little. It is noticeably cooler, to the point that you can handle it without gloves within 10 minutes. using less acetylene is only a minor benefit to me.
I cant completely turn off the fuel though, or the cut wont sustain itself very long, maybe a couple of inches. does anyone have experience with this type of cutting? Is it common? can anyone give some general rules to follow or possible hints, is it possible to cut without any flame at all once the cut has been started? As a general rule, would you keep the same oxy pressure as for a flame cut? should travel speeds be about the same?
Any hints or book reccomendations would be appreciated!