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TM 10-3930-633-34
is evident, retap the hole for the next oversize
a. In those cases of emergency where welding
repair is apparently the only practical means of
screw or stud. When retapping will result in
restoring the serviceability of the vehicle, the
weakening the part, or when the cost of the part
m a k e s retapping impractical, replace the
instructions given below must be rigidly followed.
b. Personnel should be cautioned against
damaged part. At times, merely chasing the
adding brackets and attachments by welding for
threads with the proper size tap or die will be
personal interests. The nature of this practice
adequate.
invites disregard for good welding design,. as well
2-10. General Reassembly
as creating unnecessary visibility problems for
a. Remove protective grease coatings from new
the operator.
parts prior to installation.
2-13. Welding Practices
b. To replace a preformed packing, first
The surfaces of parts to be welded shall be free
dovetail groove, then stretch packing and place
from paint, grease,  and scale which can be
into position. Rotate component on flat surface,
removed by chipping and wire brushing, and
applying a downward pressure to uniformly press
other foreign matter. When multiple layers of
the packing into position.
weld metal are required, each layer shall be
c. To provide added sealing for gaskets, coat
thoroughly cleaned before depositing another
both sides with non-hardening oil resistant
layer. All welded parts and assemblies shall be
sealing compound (MIL-S-45180B). Be sure that
free from cracks and other imperfections that may
all traces of previous gasket and sealant are
reduce the effectiveness of the part or assembly.
removed before installing new gasket,
All weldments shall be free from slag, flux, weld
d. Install oil seals with seal lip facing in,
spatter, and other impurities detrimental to the
applying an even force to the outer edge of seal.
strength and soundness of the weld. Work shall
Coat oil seals evenly with oil or grease before
be positioned for flat welding whenever prac-
installing. If oil seals are to be installed over
ticable. Butt type joints having members of equal
keyed or splined shafts, use a guide to prevent
thickness shall be aligned within 10 percent of the
sharp edges of the keyway of splines from cutting
thickness of the members involved. Weldments
the leather or neoprene seal. Guides can be
shall be free from overlays. Undercut in weld-
constructed of very thin gage sheet metal and
ments of type 2 and type 3 steels shall not be more
shaped to the required diameter. However, make
than 0.01 inch deep when its direction is trans-
certain the guide edges are not sharp and are bent
verse to the primary stress in the part that is
slightly inward so they do not cut the seal.
undercut. Undercut shall be not more than 1/32-
e. During reassembly of shafts and bearings in
inch deep when its direction is parallel to the
housing, first mount bearing on shaft, then install
primary stress in the part that is undercut.
the assembly by applying force to the shaft.
When mounting bearings on shafts, always apply
2-14. Pre-inspection
force to the inner races.
a. The area of the machine to be repaired must
f. Lubricate all preformed packings with a thin
be thoroughly cleaned. Steam-cleaning of the
coating of light mineral oil before installation.
entire machine is recommended.
g. Lubricate bearings prior to reassembly with
b. It must be remembered that whenever a
the type of lubricant normally used in the related
failure occurs in any component, the same shock
housing or container. This will provide lubrication
forces causing the failure have been present
during the first run-in until lubricant from the
elsewhere in that component, and have been
system can reach the bearings.
transmitted throughout the structure wherever
there is resistance to that force. Because of this
2-11. Repair Welding
factor, a thorough inspection of all members and
2-12. General
weld joints so affected must be made, such as:
The manufacturer has historically opposed field
(1) Reactive frame members
repair of critical components of any of their
(2) Spring shackles
products. It is recommended, rather, that the
(3) Engine mounts
failed or damaged component be replaced at the
(4) Transmission mounts
lowest serviceable level. The manufacturer does,
c. The use of magnetic particle and/or dye
however, recognize that situations may arise in
penetrant techniques of nondestructive testing
which replacement of the part(s) is not feasible for
for this inspection are highly recommended.
reasons of time limitations, spare parts short-
ages, etc.
2-10

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