between the tip and the mixing head. When the
removable tips are used with an extension tube, they
are made of hard copper, brass, or bronze.
Tip sizes are designated by numbers, and each
manufacturer has an arrangement for classifying them.
Tip sizes differ in the diameter of the hole to obtain the
correct volume of heat for the work to be done.
HOSE.Hose used to make the connection
between a torch and a regulator is strong, nonporous,
and sufficiently flexible and light to make torch
movements easy. It is made to withstand high-internal
pressures. The rubber used in its manufacture is
specially treated to remove sulfur to avoid the danger
of spontaneous combustion. Welding hose comes in
various sizes, depending upon the size of work for
which it is intended. Hose used for light work is 3/16-
or l/4-inch-inside diameter, and it has one or two plies
of fabric. For heavy-duty welding and cutting
operations, hose with a 5/16-inch-inside diameter and
three to five plies of fabric should be used. Single hose
comes in lengths of 12 l/2 feet to 25 feet. Some
manufacturers make a double hose that conforms to the
same general specifications. The hoses used for
acetylene and oxygen are the same in grade, but they
differ in color. Oxygen hose is GREEN; MAPP-gas
hose is RED.
Use no oil, grease, or other lubricant on weld-
ing (or cutting) apparatus. Oil or grease in the
presence of oxygen under pressure ignites
FILLER RODS is the term that refers to a filler
metal, in wire or rod form, for use in gas welding and
brazing processes and certain electric welding
processes when the filler metal is not a part of the
electric circuit. A filler rod serves only one purpose; it
supplies filler metal to the joint.
Filler rods for steel are often coated with copper to
protect them from corrosion during storage. Most rods
are furnished in 36-inch lengths and a wide variety of
diameters, ranging from l/32 to 3/8 inch. Rods for
welding cast iron vary from 12 to 24 inches in length
and are frequently square, rather than round, in cross
section. The rod diameter selected for a given job is
governed by the thickness of the metals being joined.
Except for the rod diameter, the filler rod selected is
determined by military (MIL) specification on the
basis of the metals being joined.
Many different types of rods are manufactured for
welding ferrous and nonferrous metals. In general,
welding shops stock only a few basic types that are
suitable in all welding positions. These basic types are
known as general-purpose rods.
SELECTION OF TORCH TIP.Welding
torch tip size is designated by a number stamped on the
tip. The tip size is determined by the size of the orifice.
There is no standard system of numbering welding
torch tip sizes; each manufacturer has a numbering
system. In this manual, tip size instructions are
provided in orifice Numbers drill size. Number drills
consist of a series of 80 drills, Numbers 1 through 80.
Once you know a manufacturers torches and
numbering. system, you rarely have to refer to orifice
number drill sizes.
Since the orifice size determines the amount of
acetylene and oxygen fed to the flame, the orifice
determines the amount of heat produced by the torch.
The larger the orifice, the greater the amount of heat
generated. For practical purposes with a balanced,
pressure-type torch, use table 3-3.
If the torch tip orifice is too small, not enough
heat is available to bring the metal to its melting and
flowing temperature. If the torch tip is too large,
poor welds result because the weld has to be made
too fast. the welding rod melting is hard to control,
Table 3-3.Welding Rod Sizes and Tip Sizes Used to Weld
Various Thicknesses to Metal
*Sizes listed in this table are approximate
and provide satisfactory results. The size of the
piece being welded will govern the tip choice.
When welding small pieces, use a smaller tip and
welding rod. When welding larger pieces, use a
larger size tip and welding rod.