Ridge, give this a try. I'll use a victor #2 tip for an example. Open your valves on the torch all the way now adjust your acetylene regulator till you get some gas flow and light the torch. Now keep increasing your regulated gas till the flame leaves the tip. This will probably be some where around 3 or 4 psi. That is the absolute max pressure that the #2 tip can handle. For any condition now 2 to 3 psi will supply enough acetylene.
Now with your acetylene flame lit and at its max opening (with out it leaving the tip) adjust your oxygen regulator till you have a neutral flame. For this #2 tip this will probably be around 4 or 5 psi. So this is the maximum oxygen pressure that you will need for the maximum acetylene that the #2 tip can handle.
You can use this procedure to determine the range of pressures for any welding, cutting or heating tip. Keep a chart and you will know for sure exactly where to set your gauges. Stu’s reply is also valid as most welders just use a higher setting to cover most of their needs.
As a general rule I personally wouldn’t run my oxygen regulator much above 8 or 10 psi and the acetylene at 4 to 5 psi unless like Stu said, you were heating or burning with a very large tip.
Also if you’re new to gas welding remember, 1/4 TURN on the Acetylene and FULL open on the Oxygen. This is in case you have a hose/torch/regulator fire you can kill the Acetylene quick and the oxygen being high pressure has a double seat and can leak past the packing nut unless you fully seat it open.
Have fun and stay safe.
Denny Graham
Sandwich, IL

Denny G
Sandwich, IL