FLAME-CUTTING

[Music] oxy acetylene flame cutting is the quick and easy way to slice through iron and steel intense flames heat a spot almost to melting then a jet of oxygen directed against the heated area cuts a narrow slit or kerf through the metal as the stream of oxygen combines with a hot metal it forms liquid iron oxide or slag this slag is blown away exposing fresh metal to the cutting action of the oxygen jet straight curved or irregular cuts can be made with equal ease by guiding the blowpipe in the desired direction practice on half inch steel plate for your first lesson clean the plate with a wire brush to remove dirt rust or scale that can slow down cutting action mark the line of cut with a piece of soapstone and then use a prick punch to make dots about 3 8 of an inch apart when the soap stone is burned off by the flame the punch marks will remain as a guide to follow hold the blowpipe in your right hand with your fingers on the cutting oxygen lever rest your left hand on the plate to support the blowpipe notice that when you use your left hand as a pivot the nozzle follows an arc rather than a straight line here's an easy way to make a straight cut hold your left hand in this position with the blowpipe at the center of the cut roll your hand to the right bringing the nozzle to the starting point then follow the line of cut rolling your hand to the left as the blowpipe moves now the nozzle travels in a straight line you try it place your left hand on the plate and the nozzle at the center of the cut roll your hand to the right that's it now move the blowpipe to your left as though you were cutting practice this motion until you can do it smoothly select the correct nozzle size and adjust the oxygen and acetylene pressures as shown in your cutting chart for half inch steel roll your sleeves down and button your collar for protection from sparks wear a hat and goggles and turn your trouser cuffs down oxy acetylene cutting is as safe as sawing wood if you observe a few sensible precautions light the blowpipe and adjust the preheat flames to neutral then press the cutting oxygen lever and readjust the preheat flames if necessary to get them back to neutral hold the flames over the start of the cut to preheat both the top of the plate and the side edge here's what happens the preheat flames bring a small spot of metal almost to the melting point then the cutting oxygen stream is directed against the spot as molten slag forms it is blown away by the pressure of the oxygen stream the metal along the line of cut is removed leaving a slit or curve when the metal becomes bright red slowly open the cutting oxygen valve by pressing the lever when the cut is all the way through the plate tilt the nozzle forward slightly in the direction to be cut move the blowpipe to the left just fast enough to make a clean cut make several straight cuts to get the feel of it look down into the cut as you work this will enable you to check the speed of cutting if you move the blowpipe too fast you will lose the cut like this release the cutting lever here's what happened the blowpipe moved so fast that the metal didn't have time to reach the kindling temperature you need more heat to support the cutting action restart the cut just as you did at the edge of the plate preheat with a nozzle held vertically then tilt back toward the cut as you open the cutting oxygen valve when the cut is all the way through the plate tilt slightly forward again in the direction of cutting you will soon learn to judge the correct cutting speed for any thickness of metal keep the end of the nozzle about a quarter of an inch above the plate this will result in a smooth narrow cut like this if the flames are too close the top edges of the cut melt over like this if they are too far away the heat and oxygen stream spreads and the cut will be too wide and ragged like this one in making long cuts cut about four inches at a time this will make it easier to keep a straight line restart the cut in the scrap portion of the plate to change the direction of cutting slide the blowpipe through your left hand toward or away from you keep the blowpipe nozzle in a vertical position and practice making short sharp turns without stopping as you change direction move the blowpipe slowly enough to maintain cutting action quickly enough to get clean even edges beveling is an important cutting operation when beveling the depth of cut is greater than the plate thickness a 45 degree bevel on half inch plate is about 11 16 of an inch so you use the nozzle and oxygen and acetylene pressures recommended for three-quarter inch plate remember to adjust the preheat flames to neutral as you did before then press the cutting lever and readjust the preheat flames if necessary preheating takes a little longer here because the heat bounces off the metal when the metal becomes bright red press the cutting oxygen lever slowly as cutting starts draw the blowpipe toward you keep the angle of the blowpipe constant as you move along practice until you can produce a smooth even surface like this to cut a circle or shape near the edge of the plate start at the edge as in straight line cutting keep the nozzle vertical as you follow the line look down into the cut to check the speed of cutting when cutting a shape away from the edge start by piercing a hole in the scrap portion of the plate the actual piercing takes only a moment so let's study it in animation first preheat a spot until it turns bright red keep the nozzle tip about one quarter inch from the plate at which point the pale blue cones of the flames almost touch the surface as the surface starts to melt raise the blowpipe until the nozzle is a half inch above the plate this prevents molten slag from blowing up and clogging the nozzle press the cutting oxygen lever slowly and start to move the blowpipe in a small circle this keeps the slag from blowing back at you continue the circling motion until you have cut through the plate now lower the blowpipe until the nozzle again is a quarter inch above the plate remember these steps preheat until the metal turns red raise the blowpipe press the cutting lever lower the blowpipe when the cut has pierced the plate keep the nozzle vertical as you continue to cut let's review the main points of flame cutting first clean the metal and mark the line of cut with soapstone and prick punch select the proper nozzle for the thickness of metal to be cut using the cutting chart as a guide set oxygen and acetylene pressures as shown on the chart follow common sense precautions on safety remember safe cutting is efficient cutting when starting a cut preheat the top and side edge of the plate when the metal glows bright red tilt the nozzle so that the flames point toward the edge of the plate as cutting starts straighten the nozzle judge your cutting speed by looking down into the cut when beveling keep the blowpipe angle constant to pierce a hole start to preheat with a nozzle a quarter inch above the plate raise it to a half inch as cutting starts then lower it again as you pierce the metal with practice flame cutting becomes easier and easier to do you will find more and more uses for it [Music] your hand blowpipe will cut steel from a sixteenth of an inch to twelve inches in thickness equipment for extra heavy duty slices through as much as five feet of solid steel plane cutting will serve you in a thousand ways from scrapping obsolete equipment to shaping precision parts for the farm or shop oxy acetylene flame cutting is the fastest way to cut metal your cutting blowpipe is one of the most important tools you own you