The steps involved in repairing a damaged
assembly or disassembly. Do this with great care and
threaded hole with a screw thread insert are as
only with proper supervision. This chapter explains
the operation of the oxyacetylene torch used to heat
parts only. It also covers the safety precautions you
1. Determine the original threaded hole size.
must observe when you use the torch and related
Select the correct standard-sized screw thread insert
with the length that best fits the application. Be sure
the metal from which the insert is made is
recommended for the particular application.
cylinder of acetylene, a cylinder of oxygen, two
regulators, two lengths of hose with fittings, a
2. Select the correct tap for the insert to be
welding torch with tips, and either a cutting
installed. Some taps come in sets of a roughing and a
attachment or a separate cutting torch. Accessories
include a spark lighter to light the torch; an apparatus
3. Select the correct size of drill based on the
wrench to fit the various connections, regulators,
information on the shank of the tap or from charts
cylinders, and torches; goggles with filter lenses to
normally supplied with the insert kits. Measure the
protect the eyes, and gloves to protect the hands.
part with a rule to determine if the previously
Wear flame-resistant clothing when necessary.
referenced minimum distance from the hole to the
Acetylene (C2H2) is a fuel gas made up of carbon
edge of the part exists. With all involved tools and
and hydrogen. When burned with oxygen, acetylene
parts secured rigidly in place, drill the hole to a
produces a very hot flame with a temperature between
minimum depth that will permit full threads to be
5700° and 6300°F. Acetylene gas is colorless, but has
tapped a distance equaling or exceeding the length of
a distinct, easily recognized odor. The acetylene used
the insert, not counting any spot-faced or countersunk
on board ship is usually taken from compressed gas
area at the top of the hole. Remove all chips from the
Oxygen is a colorless, tasteless, odorless gas that
4. Tap the hole. Use standard tapping procedures
is slightly heavier than air. Oxygen will not burn by
in this step. If the tapping procedure calls for both
itself, but it will support combustion when combined
roughing and finishing taps, be sure to use both taps
with other gases. You must be extremely careful to
make sure compressed oxygen does not become
improve the quality of the threads. When you have
contaminated with hydrogen or hydrocarbon gases or
completed the tapping, inspect the threads to make
liquids, unless the oxygen is controlled by such means
sure full threads have been cut to the required depth of
as the mixing chamber of a torch. A highly explosive
the hole. Remove all chips.
mixture will be formed if uncontrolled compressed
5. Next, install the insert. If the hole being
oxygen becomes contaminated. NEVER let oxygen
repaired is corroded badly, apply a small amount of
come in contact with oil or grease.
The gas pressure in a cylinder must be reduced to
installing the insert. Position the insert on the insert
a suitable working pressure before it can be used.
tool as required by the particular style being used.
This is done with a regulator or reducing valve.
Turn the tool clockwise to install the insert. Continue
Regulators are either the single-stage or the
to turn the tool until the insert is approximately 1/2
double-stage type. Single-stage regulators reduce the
turn below the surface of the part. Remove the tool by
pressure of the gas in one step; two-stage regulators
turning it counterclockwise.
do the same job in two steps, or stages. Two-stage
6. Use an approved antiseize compound when
regulators generally require less adjustment.
screwing the threaded bolt or stud into the insert.
Avoid using similar metals such as a stainless insert
The hose used to make the connection between
and a stainless bolt to prevent galling and seizing of
the torch and the regulators is strong, nonporous, and
light and flexible enough to make torch movements
easy. The hose is made to withstand high internal
pressures. The rubber from which it is made is
specially treated to remove sulfur to avoid the danger
As an MR, you may have to use an oxyacetylene
torch to heat parts to expand them enough to permit
various sizes, depending upon work for which it is