(9) Machined and drilled surfaces shall be visu-
(5) Never attempt to make arbors from nuts and
ally inspected for indications of delamina-
bolts for any cutter.
tions, excessive iber breakout or overheat-
ing. Surfaces exhibiting these indications
(6) Make sure tools and cutters are in good
shall be further inspected ultrasonically to
condition before installing and using in air
determine the extent of damage. Surfaces
motors (no bent shanks or loose hardware).
of machined and drilled parts shall have a
smooth, polished appearance as opposed to
(7) Never hold small parts in your hands for
a dull, rough surface as determined visually.
machining or drilling. Always secure parts
properly before beginning work.
(8) Always secure loose clothing (sleeves, etc.)
when using rotating equipment.
Do not use oil-based coolant. Do not use any
type of coolant when holes will penetrate into
(9) Always start router motors before applying to
bonded honeycomb or foam core structure.
(10) Coolant can be used in conjunction with the
(10) Never attempt to hold a vacuum cleaner
cutting tool to ease the cutting process by
hose with one hand while operating equip-
removing debris and reducing heat buildup.
ment with the other hand.
It also extends cutter life and provides some
control of dust. A high pressure, light spray
(11) Always wear the personal protective equip-
mist of water or air can be used when drilling
and reaming laminates alone or in com-
bination with metallic substructure. Non
6-9. CARBON- EPOXY, CARBON-BISMALEIMIDE
cetyl alcohol, and oil-free Freon may be
AND CARBON-POLYIMIDE REPAIRS. Carbon ibers
used when authorized by the system spe-
are brittle and have a tendency to break and pull
ciic technical manual. Coolant becomes
out of the laminate if not machined properly. Care
more important as the thickness of the lam-
must be exercised to not force the tool or exces-
inate increases. The composite should not
sive material removal will result. Speeds and feed
exceed 140 °F during drilling or machining.
rates are important. Because most composite parts
Often, holes can be drilled successfully on
are fabricated in layers or plies, forcing cutters into
thin carbon laminates without the use of
the material and not supporting the backside of the
coolant. Coolant use is mandatory when
area being machined can create ply separations or
machining boron iber-reinforced materials.
Do not use coolant when cutting or drilling
a. Repair Tools. Different types of carbon-epoxies
require varying tools to achieve the best repair. The
d. General Air Tool Safety. Air tools operate at
following paragraphs identify the recommended tools
high revolutions per minute (RPM) and can cause
for the type of epoxy being repaired.
injury if not used properly. These are general safety
instructions to know and follow when using air tools.
(1) Woven Carbon Laminates. Woven carbon
laminates can be machined with most conventional
(1) Always disconnect air supply hose from tools
tools. However, the abrasiveness of the carbon
before changing cutters or making adjust-
degrades the quality of the cut and drastically reduces
ments to attachments.
cutter life. To overcome this disadvantage, machining
should be done with carbide or diamond-coated tools.
(2) Chuck keys or collet wrenches must always
be removed from tools before reconnecting
air supply hose.
(2) Unidirectional Carbon Laminates. Unidire-
ctional carbon laminates are more susceptible than
(3) Use only sanding disks and disk holders with
woven laminates to delamination and splintering at
positive locking features incorporated.
the entrance and exit of the cutting tool. Depending
on the orientation of the materials, delamination and
(4) Observe the safe speed rating of cutters,
splintering can propagate extensively from improper
drums and sanding disk holders. The safe
speeds, feeds, and use of the wrong cutters. Carbide
speed must be equal to or greater than the
or diamond-coated tooling should always be used on
speed of the tool.
unidirectional carbon laminates.