Hard-
Surfacing,
Building
Fusion
Welding
Carbon
Welding Non-Ferrous Metals
Heating
& Heat
Treating
Braze
Welding
Welding Cast Iron Welding Ferrous Metals
Brazing
&
Soldering
Equipment
Set-Up
Operation
Equipment
For
OXY-Acet
Structure
of
Steel
Mechanical
Properties
of Metals
Oxygen
&
Acetylene
OXY-Acet
Flame
Physical
Properties
of Metals
How Steels
Are
Classified
Expansion
&
Contraction
Prep
For
Welding
OXY-Acet
Welding
& Cutting
Safety
Practices
Manual
Cutting
Oxygen
Cutting By
Machine
Appendices
Testing
&
Inspecting
1
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TESTING AND INSPECTING Whenever materials are manufactured some procedure has to be established to determine whether the manufactured material or part meets the requirements that have been established. In the steel mill, samples are taken periodically from the furnace and checked to make sure that the chemical analysis of the steel is correct. After the ingots have been cast and are being rolled, they are visually examined to determine whether there are cracks or other defects present, and any defects found are removed before the work progresses. In the foundry and forge shop, the manufactured articles are examined to make sure that there are no holes in them and that they are of the size required. In the machine shop parts are gauged or otherwise measured to make sure that they are of the right dimensions. The completeness of any testing program and the carefulness of the inspection will depend naturally upon the requirements. It is obviously useless to use micrometer calipers on a part that is being rough-forged, and it is equally useless to check the measurements of an airplane motor cylinder with a foot rule. In the same way, it is a waste of effort to X-ray all the welds in a clothes locker; yet serious difficulty could occur if nothing were known about the corrosion resistance of the welds in a chemical piping system. Factor of Safety A part obviously need be no better than demanded by the requirements of service. It is important, however, that every service condition that is likely to be encountered be taken into consideration in the planning. A tent made out of ordinary cloth is sufficiently good to keep off the night dew, but if one expects to stay dry in a rainstorm, the cloth of the tent must be waterproof and a trench must be provided around the tent to make certain the water does not flow in underneath. If the rain is to be accompanied by a strong wind, the tent must be erected substantially enough not be blown over, an event that would make all the other precautions useless.