3-95. BLANKING. Blanking is usually accomplished utilizing a blanking die in almost any type of punch press
equipment. The essential factors requiring control are die clearance, shearing edge lead, and stripping action. The
shearing principle is primarily the same as that encountered with the squaring shear. However, the method of grinding
punch dies will vary according to the results required and in such manner that will reduce load on equipment. Commonly
two or more high points are ground on die to keep side thrust on the punch at a minimum. Lubrication is essential in
blanking operations. Suitable lubricants are engine oil, kerosene and lard oil which are normally used in mixed form.
3-96. JOINING ALUMINUM.
3-97. WELDING. Aluminum and its alloys that are considered practical to weld, can be welded satisfactorily by using
metal-arc, carbon arc, atomic-hydrogen, inert-gas shielded arc, and gas welding. Almost all alloys can be joined by
resistance welding such as spot, seam welding, and flash welding.
For general welding procedures, see T.O. 34W415.
3-98. Aluminum differs in welding characteristics from that of steel in that the melting point is much lower. For example,
pure aluminum melts at 1216°F and the alloys melt at even lower temperatures as compared to approximately 2500° F
3-99. Aluminum oxidation is another factor that requires understanding and control. Aluminum oxides form a film or
coating on all exposed surfaces. This must be removed before welding. Removal is frequently accomplished by use of
flux which combines chemically with the oxide to form a fluid slag. Due to the apparent weakness of aluminum alloys to
withstand high temperature and the high degrees of thermal conductivity, adequate support is necessary for all the areas
of parts subjected to appreciable temperature rises. If the above precautions are not taken difficulty will be encountered
with shrinkage warpage and reaction stresses. Aluminum does not change color at any temperature up to and including
the melting point, therefore, it is necessary for the welder or operator to watch the "wet" appearance of the surface which
indicates surface melting. This is contrary to ferrous metals where the color of the heated piece indicates the
3-100. There are basically two factors that determine whether an aluminum alloy can be welded by a particular process.
They are percentage of copper content and magnesium content. High copper (3-4% or more) causes embrittlement of
weld metal and considerable loss of mechanical properties of adjoining metal when fusion welded. Thus aluminum alloys
with an appreciable content of copper and not recommended for fusion welding. A high magnesium content alloy tends
to produce a heavier oxide coating and these alloys are not recommended for brazing or soldering operations where
oxide formation is a critical factor.
When performing any welding operation safety precautions shall be taken to prevent injury to
personnel, other equipment and to prevent fire. Wear eye, face, hand shields, consult local
safety officer for specific instructions.
3-101. FUSION WELDING. The common non-heat treatable alloys are the most easily fusion welded i.e., 1100, 3003,
3004, 5050, 5052, 5056, etc. An exception to the above is 6061 which is weldable, and heat-treatable. 6061 material is
normally used where strength and weldability is a required factor. Due to the many methods employed for fusion welding
aluminum and the many variables encountered this publication will be limited to the most common types which are gas
welding and inert gas shielded arc (heliarc and argon arc). Gas welding was one of the earliest successful processes
employed for welding aluminum and is generally used.
3-102. WELDERS TRAINING AND QUALIFICATION . Personnel assigned to accomplish aluminum welding .should be
trained in the handling of equipment fabrication procedures i.e. composition and identification of aluminum alloys,
jigging, tacking, cleaning and treating, blue print reading, safety, use of tools (hand and machine) and to meet
3-103. Tests for Aircraft and Missile Welding Operators qualifications are cited in Specification MIL-STD-1595 and T.O.
00-25-252. This specification and technical order are intended for use in ascertaining that welders to be engaged or that
are engaged in welding aircraft, aircraft parts and accessories, missiles, missile parts, pressure systems, and
accessories, possess and maintain a satisfactory level of proficiency. Periodic tests should be made to assure that
welders qualifications are maintained in addition to test and inspection of parts as required by drawings, specifications,
technical orders and other technical data. The primary factor involved in the fabrication of any part is that it will meet
requirement set forth and this requirement shall not be waivered because the work was accomplished by a qualified
welder/ or person.
3-104. GAS WELDING OF ALUMINUM . Oxy-acetylene or oxy-hydrogen are the two common processes utilized as
heating media. Other types may be used such as oxy-butane, oxy-propane and oxy-natural gas, etc., but they are more
costly and welding speeds are slower.