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Hi Bob, Since I previously covered this topic, I'll just repost my thoughts: UpDated 03/26/05: A trick I use for accurate free hand cutting is using a sanding disc to knock off the heavy scale and then use a scratch awl for my lines. The line is very thin so it makes following lines very easy. Another is to stop cutting when you feel your hands or torch get out of balance. When that happens, stop and reposition the torch then continue cutting. The cleanest cut comes from a clean tip. After you clean all the orifice bores in the tip, fire up the torch and set flame for cutting, then depress the cutting lever and observe the flame. There should be a long very "uniform" inner flame cutting cone. If that inner cone is not "very" uniform then your cut will be ragged just like the flame cone is and the back of the metal will have slag. Reclean the center orifice until it's very uniform. A cut with a clean tip will have a very smooth cut surface with very little (if any) slag on the backside of the cut. If either one of these is not present reclean the tip. The center bore orifice can get deformed and the tip needs replaced or cut off. It's really important to hold the cleaning file straight in the bore hole and just removing enough material to clean the bore to make the tip last a long time. I've never used a new tip that was clean enough for cutting right out of the box. To expand on my thoughts: Altough theres many different tip sizes, I have a found a No3 makes for a all around good cutting tip as it will cut upto 1-1/2" or 18ga sheet metal depending on the preheat setting. Another consideration is as the tip size becomes smaller so does the orifice size and it becomes a bare to clean them ity bity holes. If using an automatic cutting machine then changing tip size would be a production benefit. Setting the proper neutral preheat flame, the orifice holes around the center cutting orifice, can be observed by the tip of the inner flame cone. A neutral flame has a blue colored flame outer sheild with a light blue to white inner cone flame that is slightly rounded at the cone tip. A oxidizing flame (too much oxygen) has a sharp pointed very white inner cone. A reducing flame (not enough oxygen) would have a very round to a ragged thrid inner cone. I have found 5psi acetylene and 30psi Oxygen while cutting to be a good all around setting for upto 50ft of 1/4" hose. Your final pressure setting is regulated by the needle valve adjustments on the mixing body. For brazing or welding a size #0 tip works well with 5psi Acetylene and 20psi Oxygen. Again the needle valves on the mixing body sets the final pressure needed at the tip. I also use the above settings to preheat 2" round bar without any problems using the #0 size tip or the rose bud tip. The advantage to using a rose bud tip is that it expands the flame temperature over a wider area vs using a #0 size tip. I very seldom use my rose bud tip. Preheating with LP saves some expensive gas then finish heating with Qxy/Acet. Never run Acetylene above 15psi for any reason! T_Bone
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