Repair

necessary and check for broken welds, loose

material covered in this procedure is Type 355-

rivets or weld nuts. If parts are cracked or torn,

T71

Federal

Specification

QQ-A-601.

they must be repaired or replaced. Check shroud

(2) E q u i p m e n t . An alternating current arc

welding m a c h i n e s h a l l b e u s e d f o r h e l i a r c

seals for hardness, tears, or other damage. Mark

welding. Class 4043, conforming to Specification

damaged seals for replacement if the part is

otherwise serviceable.

QQ-R-566a or MIL-E-16053 welding rod, is

compatible with the base material and shall be

6 - 4 . Repair

used for all welding repairs in this material

General. Most engine parts and com-

group. All equipment shall be consistent with

ponents may be repaired as outlined below. After

good

standard

welding

practices,

and

ac-

repair, clean all parts thoroughly to prevent

ceptable to the Government Inspector.

metal chips from repair operations, or abrasives

(3) P r o c e s s e s .

used in repair operations, from entering working

(a) MIG (Metal Inert Gas) process. T h e

parts of the engine.

MIG process is recommended when welding

General

Repair

Castings.

1/8

inch

aluminum plate greater than

(1) Replace all castings when cracks have

thickness.

penetrated high stress areas such as fillets or

(b) TIG (Tungsten Inert Gas) process.

webbing.

When

welding aluminum plate 1/8 inch thick

(2) Replace all castings which do not

and under, the TIG process is recommended.

conform to tolerances specified in the ap-

(4) C a s t i n g p r e p a r a t i o n .

propriate repair and rebuild standards table.

(a) C l e a n i n g . All foreign material must

(3) Replace all castings on which machined

be removed from the area to be welded prior to

surfaces are burred or nicked to the point of

repair operations. The area shall be cleaned

impairing

subsequent

assembly

operation.

using a stainless steel wire brush, drill, burring

Repair minor damage to machined surfaces with

tool, or approved chemical process, whichever is

a fine mill file or crocus cloth dipped in dry-

applicable.

cleaning solvent or mineral spirits paint thinner.

(b) C r a c k s . Determine flow of cracks by

(4) Replace all castings having flanges

using dye check method. Drill stop holes at crack

which are severely warped and cannot be

ends with a 1 / 4-inch drill and mill out cracks to

repaired to provide a proper seating surface with

provide a "V" aperture.

its

mating

part.

Repair

minor

warpage

Check

area

around

the

mounting flanges and mounting pads by working

fracture for cracks using dye check. Drill stop

surface across a sheet of crocus cloth held tightly

holes at the ends of detected cracks with a 1/4-

on a surface plate or similar flat surface.

inch drill and mill out crack to provide a "V"

(5) Repair damaged pipe threads in tapped

aperture.

holes with a used tap.

(d) Missing metal. If the size of the

Note. Pipe plug threads in castings must be

damaged area permits, mill out and chamfer that

in good condition to prevent oil leakage.

area to 30 degrees to provide a 60 degree in-

c. W e l d i n g o f A l u m i n u m A l l o y

Castings.

cluded angle. The insert piece required for this

Note. The following procedures

(1) through

area must be identical in composition and may

(7) are based on the applicable paragraphs in

be cut from scrapped castings or suitable sheet

Specification MIL-W-8604 and MIL-W-45205,

stock. Fit insert piece into milled area, so that

and outline the requirements, equipment, and

1/6-

1/8-inch

maintained

between

insert

welding process used for the repair of aluminum

and

casting

wall.

alloy castings. Specific information relating to

Precisely

(5) P r e p a r a t i o n f o r w e l d i n g .

the welding of individual castings will be covered

measure castings at appropriate locations to

in the appropriate section of this chapter.

detect dimensional changes caused by welding

(1) O p e r a t o r . Welding shall be performed

repair. Record dimensions for checking after

by welding operators who have successfully met

repair has been made to be sure that critical

the requirements of Specification MIL-T-5021,

dimensions have been held.

for

Material

Group

(Aluminum

Alloys).

Preheat

(6) Preheat prior to welding.

Operational:

TM 9-237 (Nov. 1967). The base

6-5