When man started to melt and cast metal he would pour the molten metal into a mold, usually formed in the sand. If he wanted to join two or more of these "castings" he would place them close together and pour more molten metal where they touched. This would melt the edges of the two castings and upon cooling join them with weld. This is a basic welding process.
Frederick M Bowers invented the first Welding Helmet on April 13, 1915. But I'm not sure where he lived or where the invention took place!! Please improve this answer if you do hear anything!! Ali x Maybe the question isn't about welding helmets but welding. If so, welding was first performed during the Bronze Age. Melting and casting metals (Copper, Brass, etc) and when 2 or more castings needed to be joined they were placed close together and molten Copper, Brass, Bronze was poured so that the puddle would melt the edges producing a "weld" joint. The term Welding means to melt the base material whether it is metal, glass, plastic or some other material.
Faces- 20 Edges- 30 Vertices- 12
When there are directed edges in the graph, as it is impossible to move back from B to A when the edges are directed.
It has 8 faces, 6 Vertices, and 12 edges * * * * * That is one configuration. An octahedron can also be a heptagonal pyramid which has 8 faces, 8 vertices and 14 edges.
Deburring.
Waste edges!
To stop the edges of the material from fraying.
The sealing material should extend least 2 inches past the edge of the wound.
Ejecta
at least 2 inchs ^(>.<)> SABC <(>.<)^
The waste material at the edges of a roll of woven cloth is called selvage. It is the self-finished edge that prevents the fabric from unraveling or fraying.
When man started to melt and cast metal he would pour the molten metal into a mold, usually formed in the sand. If he wanted to join two or more of these "castings" he would place them close together and pour more molten metal where they touched. This would melt the edges of the two castings and upon cooling join them with weld. This is a basic welding process.
Obsidian was known to primitive peoples who fashioned this material into points for weapons and into edges for tools. In that light, no one "discovered" this amazing material we sometimes call volcanic glass. It was "discovered" well in excess of ten thousand years ago. Its use predates any writing by many ages. Links can be found below to related posts and questions.
adhesive coating that is protected by a strip of brown, waxed paper?
Concave lens
outside