TB 1-1520-238-20-140
3.4.1
Clean the selected location using acetone and a lint-free cloth. Remove all oils and solids from area.
3.4.2
Lightly scuff a 1/2 inch diameter area using a Scotch-Brite pad or 220 grit emery paper. If during
scuffing, any bare metal is exposed, prime and paint the area. After the appropriate drying time, re-
scuff the area.
3.4.3
Clean the scuffed area with acetone. Dry wipe the area with a lint-free cloth before the solvent
evaporates to remove any drying residue.
3.4.4
Allow the area to dry completely (about 5 minutes), and inspect for proper surface preparation.
3.4.5
Lightly sand the black side of the CMB for a few seconds with 220 grit emery paper and wipe clean
with a lint-free cloth to prepare the back surface for bonding.
3.4.6
Mix the Hysol EA 9394 adhesive according to manufacturer's directions.
Place a small amount of Hysol EA 9394 on the back surface of the CMB.
3.4.7
3.4.8
Firmly press the CMB onto the component surface, ensuring a small bead forms entirely around the
CMB.
CAUTION
Make sure the CMB is safe from loading or jarring until proper handling
strength of the adhesive has been reached. Handling strength for Hysol
EA 9394 will occur after 8 hours at 77 F. Only if the cure inspection test is
passed (see 3.4.11 below), it is safe to fly the aircraft 24 hours after button
installation without risk of stressing the bonded joint to the point of
breaking during flight. Full cure time (7 days at 77 F or 25 C) is determined
to be the time after which the adhesive has developed maximum bond
strength, maximum environmental resistance, and ultimate performance
properties.
3.4.9
Hold the CMB with your thumb until it remains where placed.
3.4.10. Remove excess adhesive from the work area before it hardens. Use acetone for removing any
unnecessary, uncured adhesive. Do not disturb the adhesive bead.
3.4.11 To ensure proper curing of the adhesive, wait 24 hours, and test for hardness. Randomly inspect 5
CMBs or 10% of CMBs, whichever is greater. Inspect this quantity/percentage for each mixed batch
of adhesive used. The test involves using your fingernail or other object of similar hardness and
applying pressure to the bead of the adhesive.
3.4.11.1
If this test leaves a visible mark on the adhesive, then the adhesive is not adequately cured,
and operation of the component would introduce a possible FOD (foreign object damage) risk. The
adhesive might be bad, or it could just be a little cool and thus needs more time to cure. Either
remove and reinstall the CMBs (restarting at step 3.4.1) or wait and re-inspect later. If the adhesive
never passes this test, then the CMBs must be removed and reinstalled (restarting at step 3.4.1).
Either remove all CMBs installed using this mixed batch of adhesive, or remove only those for which
the cure test fails (after testing 100% of the CMBs installed with this mixed batch).
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