To butt weld two pieces of material by the oxyacetylene process (commonly called simply 'Gas Welding') it is necessary to bevel the edges (or 'chamfer' them, to use the normal term). This is done so that when the two edges are placed or 'butted' together they form a V-shaped groove.
The purpose of this V is to allow greater penetration, in fact, without the V, 100% penetration would be impossible in thicker material. Actually, anything up to Vain. (say 3mm) in thickness can be welded without any V or any edge preparation, by simply using a small gap of about V1sin. (1.6mm) between the edges, which acts instead of the V. However, this is not always possible because of limits in dimension, etc.
Therefore, for the purpose of our exercise, we will prepare the edges of our '/ein. M/S plate for a single vee butt weld by filing or grinding them to an angle of 30° on each edge. But we do not chamfer (or bevel) them to a fine knife-edge. We stop short of that, and just leave a slightly blunt 'nose' on each edge. Thus, when the two edges are lined up together, they form a V of 60° angle for most of their depth, but with
the bottom fraction vertical-sided.
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