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DRILLING

The Experience of drilling through composite is quite different than drilling through metal.

Composite can be very easily damaged so it is extremely important to follow carefully the

procedures during drilling operations

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DRILLING

Drilling data according to the specific repair

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DRILLING

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DRILLING

SRM 51-44-21

General

Hole sizes

Hole data

Drill data and drilling requirements

General requirements

Drill data

Drilling CFRP and GFRP, drilling AFRP

Drilling Composite / Metal combination

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SRM 51-44-21

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GENERAL

HOLE SIZES 1/4

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SRM 51-44-21HOLE SIZES 2/4

Hole dimension and tolerances according to the fastener and hole fit depending on the repair design

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Fasteners identification

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SRM 51-40-00

HOLE SIZES 3/4

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SRM 51-44-21

Fastener HL1011VF 6

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HOLE SIZES 4/4

Fastener ABS0257-6

Hole Tolerance

0.08 mm(0.00315 in)

0.017 mm(0.00067 in)

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Always clearance fit or close tolerance fit

Never interference fit (unlike for metal structure)

Fastener bending or turning in the hole is prevented by clamping force

FASTENER INSTALLATION

Interferences:

Even if interference are widely used in metallic structures, they should be avoided in composite structure due to possible local damage (delamination) during fastener installation. Holes are so generally drilled with a clearance fit.

In some cases ,where assembly is done between aluminium and composite parts (i.e.wing root area) moderate interference is used to minimize the aluminium part fatigue.

GENERAL REQUIREMENTS

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SRM 51-44-21

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GENERAL REQUIREMENTS

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HOLE AND DRILL DATA

Attach material to prevent any movement and use a sacrificial composite back-up material when drilling.

Drill guide tools must be used to drill at right angles with a twist-drill.

For large holes, it is recommended to drill pilot holes.

Screw pin or skin pin

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GENERAL REQUIREMENTS

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According to the material to be drilled, the drill material and drill type

DRILLING DATASRM 51-44-21

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Cutting speed Aluminium (m/min)

Cutting speed Carbone (m/min)

Cutting speed Carbone (m/min)

Cutting speed Carbone (m/min)

     

Drill with sickle-shaped grinding angle,MBBN 569

Twist drill ground on 4 faces, MBBN 570

Tapered drill-reamer

  Mini Maxi Mini Maxi Mini Maxi Mini MaxiDrill

Diameter 61 91 50 100 20 25 35 45

2.7 7200 10000 6000 12000 2300 2900 4150 5300

Cutting speed (RPM)

4.2 5000 6500 3500 7500 1500 2000 2700 34005.1 4000 5600 3200 6200 1300 1560 2200 2800

Cutting speed choice (RPM)

6000 and 8000 6000 1500 and 2500 2600 and 5000

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SRM 51-44-00

 

Cutting speed Ca / Alu (m/min)

Cutting speed Ca / Ti (m/min)

Cutting speed Stainless steel

  Mini Maxi Mini Maxi Mini MaxiDrill

Diameter 25 50 9 12 9 12

2.7 3000 6000 1000 1400 1000 1400

Cutting speed (RPM)

4.2 1900 3800 680 900 680 900

5.1 1600 3100 600 700 600 700

Cutting speed choice (RPM)

3000 700 and 1200 700 and 1200

DRILLING DATA COMPARISON

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SRM 51-44-21

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DRILLING TOOLS

Twist-drills applicable to Composite Structures

To produce holes in composite structures, it is recommended that twist-drills with special ground tips should be used. These twist-drills should be solid carbide or carbide-tipped.

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MBBN 570

TWIST-DRILL GROUND ON 4 FACESSOLID CARBIDE OR CARBIDE TIPPED

SRM 51-44-21 DRILLING TOOLS

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MBBN 569

DRILL WITH SICKLE-SHAPED GRINDING ANGLESOLID CARBIDE

SRM 51-44-21 DRILLING TOOLS

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DRILL WITH SICKLE-SHAPED GRINDING ANGLE AND LEADSOLID CARBIDE

SRM 51-44-21 DRILLING TOOLS

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SRM 51-44-21 DRILLING TOOLS

Drill – reamer for composite structure

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SRM 51-44-21

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DRILLING SEQUENCES

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SRM 51-44-21

Hole diameter range

Composilok

Tolerance

0.08 mm(0.00315 in)

0.017 mm(0.00067 in)

Hi lok

Tolerance

DRILLING SEQUENCES

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Hi lok Composilok

Pilot hole

Ream under size

Ream to size

Pilot hole

Drill to size

Drill under size

SRM 51-44-21

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Countersink defined by:- depth- angle

Depth in relation with:- fastener nominal diameter - head form (Tension / Shear)

Angle is usually 100° but may be 130° for some applications

COUNTERSINKINGREQUIREMENTS

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COUNTERSINKING

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FLUSHNESS

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COUNTERSINKING TOOLS AND SETTINGS

Depen

ding o

n the

counte

rsunk

angle

Pilot pin

Fast. hole

Pilot pin Countersunk bit

The pilot pin diametermust fit with the

fastener hole diameter.

Carbide inserts

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COUNTERSINKING TOOLS AND SETTINGS

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As defined in the SRM for fastener installation, corner must be ‘radiused’ or chamfered

CORNERREPAIR IMPLEMENTATION

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Countersunk recess

Countersunk fastener

Smooth surface

Countersunk fastener

Countersunk recess

Smooth surface

COUNTERSINKING DATA

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DRILLING DATA IDENTIFICATION

COUNTERSINKING

DRILLING SEQUENCE

DRILLING TOOLS

DRILLING DATA

GENERAL REQUIREMENTS

HOLE SIZE