Straight lengths of pipe are commonly joined by butt-welding.  Large numbers of butt-welded joints are made every day, worldwide in almost every industry. 
To prepare for making such a joint, one or both lengths of pipe to be joined must be cut to exact length and the ends prepared to receive the weld.  Usually the end of each pipe is bevelled at 37.degree.,  so that abutting the ends of the two pipes forms a symmetrical "V" groove of 74.degree.  included angle all around the joint to receive the welding bead, electric welding being taken as an example. 
Bevels are usually formed on pipe ends either by machining, which is expensive and cumbersome, or by use of a gas cutting torch. 
A gas cutting torch such as an oxy-acetylene torch has the advantages of being quick, economical, lightweight, compact and easily maneuvered, but it requires years of experience to produce best results in pipe bevelling with a torch. 
A guide has been described for use in flat plate cutting with a gas torch, in U.S. Pat.  No.  4,273,313 issued on June 16, 1981 to John M. DeNardo for GUIDE FOR A CUTTING TORCH.  This patent discloses a cam with a convex axial face for installation on a torch tip to guide on a flat plate in cutting flat work. 
In addition, large, complex, heavy automatic equipment for pipe bevelling by flame is known.