Operating instructions

6-4
6-6. FLUORESCENT PARTICLE INSPECTION.
This process, commonly known under the trade name
of "Zyglo", is recommended for inspecting aluminum
alloy parts for invisible cracks. The standard
operating technique for the process is applicable.
6-7. DIMENSIONAL INSPECTION.
6-8. INSTRUMENTS. Areas of running parts and
bushings subject to wear should be inspected for
serviceable fit with mating parts by comparative linear
measurements and alignment measurements, using
standard pattern precision measuring instruments such
as micrometer calipers, telescoping gauges and dial
indicators. The use of a dial-type cylinder bore gauge
is recommended in preference to other tools not
specifically designed for this purpose.
6-9. DIMENSIONAL LIMITS. After comparative
measurements of mating parts and determination of
running clearance, refer to the Table of Limits,
Section VI, and to the Limits and Lubrication Chart to
locate the reference number of each fit and the
acceptable limits assigned to it. Limits under the
column heading "New Parts" are manufacturing
limits. All running clearances in this column apply to
mating parts, both of which are new, and the low limit
applies in all instances; however, such clearances are
allowed to increase with wear to, but not beyond, the
values in the column headed "Serviceable Limit". All
press and shrink fits must be maintained as specified
in the "New Parts" columns when the inserted member
is replaced. Oversize parts are supplied, in some
instances, to permit conformity to this requirement.
6-10. ORIGINAL DIMENSIONS. Although
comparative measurements of mating parts will
determine the serviceability of the fit, it is not always
easy to determine which part has worn the most, and
in some instances (e.g., main journals in new bearing
inserts), accurate measurements of fit are not possible.
While no limits of wear on critical dimensions have
been assigned to specific parts in most instances, it is
helpful in estimating wear to know the original
dimensions. Hence, the manufacturing limits in Table
VIII on important dimensions of new parts should be
consulted when the serviceability of a specific part is
in doubt.
6-11. PROTECTIVE COATING. The manufac-
turer protects all aluminum alloy castings, sheet metal
and tubing from corrosion by treating all surfaces, of
the parts, with "Alodine 1200" (American Paint and
Chemical Company, Ambler, Pennsylvania 19002).
6-12. APPLICATION OF "ALODINE 1200". In
the event the original finish of an aluminum part has
deteriorated or been removed, the part may be
"Alodized" or as described in "Alodine"
manufacturer's Technical Service Data Sheet No. AL-
1200-D. Wrought or die cast (smooth surface) parts,
such as valve rocker covers and intake tubes, are
tumble blasted prior to machining, if any, to roughen
surface before treatment. Such treatment should not
be employed in overhaul work on parts with machined
surfaces. "Alodine", unlike enamel or primer, will not
flake or peel off to contaminate engine lubricating oil;
therefore, corrosion protection can be afforded to all
interior aluminum surfaces and parts. If an enamel
coating is required for a part previously treated with
"Alodine", application of a primer before painting is
not necessary. "Alodizing" will be performed after all
machining and/or repair operations have been
completed. The surface color of an "Alodized" part
may vary from light gold to dark brown. When a part
is treated with "Alodine 1200" the thickness of the
film, or build up, on the mating or bearing surfaces is
so small that the effect on dimensional tolerances is
negligible.
6-13. REPAIR OF "ALODIZED" SURFACES.
If "Alodized" parts have been remachined, rubbed
with abrasives or scratched in handling so as to,
expose areas of bare aluminum, the surface may be
repaired by local application of "Alodine" solution in
the following steps:
a. Clean bare area thoroughly with carbon tetra-
chloride. Do not under any circumstances use an oil
base solvent or strong alkaline cleaner.
b. Mix a small quantity of hot water (180°F.) with 1-
1/2 to 2 ounces of "Alodine 1200" powder to form a
paste, then gradually dilute with hot water until a
solution of one gallon is attained. This solution is to
be adjusted by addition of nitric acid to a PH value of
1.5 to 1.7.
c. Apply solution with a rubber set paint brush in such
a manner that solution flows over bare area. Allow
solution to remain on the part from one to five minutes
or until color of the new film is approximately same as
original.
d. Flush part with clear water and dry with warm air
current. Do not air blast or rub with cloth to dry new
film area. If color is too light, repeat step "C" until
desired color is obtained.