General Reassembly

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