T h i n k r e l i a b i l i t y , T h i n k H S S

DRILLING

DRILLING

DRILLING TOOLS2 Zoom on a drill3 Which HSS for maximum efficiency?4 Surface treatments for the best performance5 Vocabulary6 Choose the optimal flute length7 Choose the right design8 Other solid drill designs9 Web thickness

10 Different helix angles11 Point angles12 Examples of point designs13 Examples of point thinnings14 Benefits of point thinning15 Drill types16 Hole accuracy and positioning17 Clamping drills

DRILLING PROCESS18 The basics of drilling

19 Typical cutting speeds

20 Feeds

21 Cooling and chip removal

22 Oil-hole drills

23 How to monitor wear

24 What chips have to say

25 Solve your drilling problems

26 Tips for special drilling conditions

27 Useful drilling formulae

1

SU

MM

AR

Y

ZOOM ON A DRILL2

Surface treatmentand coating

Point shapes: design, angles, thinning

Number of teeth:from 1 to 4

Helix angle

Dimensions

Tool material

Shank types: straight, morse taper, etc.

Flute form and web thickness

WHICH HSS FOR MAXIMUM EFFICIENCY ?

• For conventionaluse

• Basic choice for industrialapplications

• For drilling ofdifficult-to-machinematerials

• For highperformancemachining

• Combines theperformance ofcarbide with thetoughness of HSS

TOOL MAKER’S TIP

Discover theperformance of

coated HSS-PMdrills, especially

when carbide drills are not

successful

3

HSS HSS-E5% cobalt

HSS-E8% cobalt

HSS-PM(powder

metallurgy)

SUCCESS STORY

Operation • Drilling of holes Ø 8.25 mm, depth 80 mmTool • Coated HSS-PM drillCutting data • vc 60 m/min, fz 0.25 mm /rev.Tool life • More than double compared with carbide (812 holes vs. 375)Cost per hole • Divided by 2 compared with carbide

Grey cast iron

SURFACE TREATMENTS FOR THE BEST PERFORMANCE

TOOL MAKER’S TIP

Chip removal iseasier with coateddrills, due to lower

friction and increasedcutting data.

DLC coatings canalso be used to drill

non-ferrous materials.

4

• Popular surfacetreatment

• For ferrous materialsonly

Steam oxide

• High wear resistance• For steels• For interrupted cuts in

difficult-to-machinematerials

• Seldom used• For cast iron and

aluminiumNitride

• High performancemultipurpose coating,for higher cutting speeds

• For ferrous alloys (steels,cast iron), hard orabrasive materials

• Suitable for dry machining

• Conventional multi-purpose coating

• Cost efficient• Medium performance

TiNGold

TiCNGrey-violet

TiAlN orTiAlCN Black-violet

MoS2 or

WC-CGrey-black

• Good anti-weldingproperties, reduces friction

• Used in combination withother coatings

• Suitable for dry machining

VOCABULARY5

A DRILL AROUNDTHE WORLD

French: un foret

German: ein Bohrer

Italian: una punta

Spanish: una brocaMargin width

Margin

Lip relief

Lip

Flut

e w

idth

Land width

Lip relief width

Body diameterclearance

Body clearance

PointFlute length

Overall length

Shank length

Sha

nk d

iam

eter

Lip relief angle

Drilldiameter

Radial corner

Core

Web Flute run-out

Point angleHelix angle

130°

Radial pointthinning

Radial point thinning

CHOOSE THE OPTIMAL FLUTE LENGTH6

TOOL MAKER’S TIP

Longer drills shouldbe used only when

strictly necessary

Flute length is one of the most critical determinants oftool life: for longer tool life, the flute length should be asshort as possible. Longer flute length results in a lowerrigidity of the drill, which causes unstable drilling

In most operations, the flute length can be calculated asfollows:Depth of hole + bush length + distance between bush and workpiece + 2x diameter (clearance for chip ejection)+ resharpening length + penetration length

Flute length (of new drill)

Length of point

Resharpening length

Penetration length Thickness of work pieceClearance for chip ejection

(2.0 x D)

Bush

Bush plate

CHOOSE THE RIGHT DESIGN

Solid twist drill

+ Multi-purpose tools

+ The widest range of diameters (from 0.05 up to 80 mmor more)

+ Available in 4 lengths: extra short, short, long, extralong

+ The longest tools (for instance 1000 mm, in diameter10 mm)

Drill with HSS indexable inserts

For drilling large holes, especially above 20 mm, or forcombined operations

+ No resharpening needed (throw-away inserts)

+ Multi-purpose tool holder, for several insert diameters

+ Auto-centering point and sharp edges for lower cuttingforces, compared with carbide inserts

+ Can be used in stacked plates and holes > 50 mm

- More fragile and not cost efficient in small diameters

TOOL MAKER’S TIP

Solid twist drills arealso suitable for highperformance drilling,thanks to advanced

designs, coatings andHSS-PM

7

The most popular

OTHER SOLID DRILL DESIGNS

Oil-hole drill

For high performance anddeep hole drilling

Double margin drill

For improved hole quality

Parabolic drill

For deep holes

Pivot drill

Increased rigidity for smalldiameter holes

Core drill

Basic choice to enlarge aholeHighly productive for IT8hole quality

Step drill

For combined operationsin one pass

Center drill

To produce the centerholes needed for turning orgrinding operations

Starting drill

For spotting andchamfering

8

Oil hole

WEB THICKNESS

Conventional

• For general purpose

• Wide chip room

• Small web thickness: 0.10~0.25 D

Medium web

• High rigidity against high feed rate.Thinnings for low thrust load arenecessary

• Used for steels and cast iron

• For high efficiency drilling andlonger tool life

• Web thickness: 0.20~0.35 D

Parabolic type

• High rigidity with smooth chipremoval

• Used for aluminium alloys andstainless steels

• Long tool life

• For deep holes, to prevent drillbreakage or curved hole

• Web thickness: 0.30~0.45 D

TOOL MAKER’S TIP

The web is the drill’sbackbone

9

DIFFERENT HELIX ANGLES

TOOL MAKER’S TIP

Do not forget that on a drill

the helix angle is the cutting angle

10

Low helix angle

Use: hard materials, bronze, brass

Also recommended for smalldiameter drills, to improve toolrigidity

+ Increases cutting edge resistance

- Increases cutting forces

Standard helix angle

Basic choice

The most popular design

High helix angle

Use: soft materials (aluminium,copper)

+ Reduces cutting forces

- Decreases cutting edge resistance

30°

POINT ANGLES

TOOL MAKER’S TIP

HSS drills offer the widest range ofpoint angles: make

use of them !

11

Small angle

Small angles: 90°

For soft materials

Standard angle

General purpose

Note: point angle has an impact onthrust load and torque as well as onthe length of the cutting edge andthe thickness of the chips

Large angle

Large angles: 130°, 135°or 140°

For hard materials

Prevents drill deviation under specialdrilling conditions (deep holes,crossing holes, lock pin holes,angular holes, etc.)

118°or 120°

EXAMPLES OF POINT DESIGNS

TOOL MAKER’S TIP

Boost drilling qualityand performance:

choose the right pointdesign

12

Conical

• Conventional drill

• General purpose

Center point

• Easy drill positioning

• Prevents burrs and vibrationswhen used for drilling thinsheets and pipes

• Use: structural steels

Four facet

• For precise holetolerances

• Recommended for smallholes

• Easy to resharpen

Double angle

• High corner resistance

• Use: hardened material,abrasive material, castiron

Spiral

• Good centering

• Reduce burrs

• Use: aluminium

The most popular

EXAMPLES OF POINT THINNINGS

No thinning

• General purpose

Three-rake

• Precise cutting edge

• For difficult-to-machinematerials or deep holes

W type

• For heavy drilling andhard materials

• Effective for prevention ofchipping

Radial point

• For heavy drilling. Goodbiting action

• Produces short, brokenchips

• Effective for reduction ofthrust load

TOOL MAKER’S TIP

Advanced HSS drillsare autocentering:

starting drills are not required

13

BENEFITS OF POINT THINNING14

Standard drill geometry (without point thinning)TOOL MAKER’S TIP

Point thinningreduces thrust forcefor improved cuttingdata, hole accuracy

and tool life

A-A Cross SectionPositive angle

B-B Cross SectionPositive angle

C-C Cross SectionNo cutting, only deformation

Advanced drill geometry (with point thinning)

A-A Cross SectionPositive angle

B-B Cross SectionPositive angle

C-C Cross SectionPositive angle

C-C Cross SectionPositive angle

DRILL TYPES15

TYPE WEB HELIX ANGLE POINT ANGLE USE

Difficult-to-machinematerials (stainlesssteels, heat resistantsteels, spring steels)

Ferrous materialsCast iron

Short chip materialsBronzeBrass

Long chip materialsAluminium alloysCopper

Easy-to-machinematerialsLong chip materials

Standard (118° or 120°)

Standard (118° or 120°)or large (130°)

Large (130°)

Standard (118° or 120°)or large (130°)

Large (130°)

Standard (30°)

Small (12 or 16°)

High (35-40°)

High (35-40°)

Medium (20-35°)

Standard web

Small web

Small web

Large webor small web

Large web

N

H

W

Parabolic

Highly rigid

HOLE ACCURACY AND POSITIONING

Standard geometry

• Tool diameter: 10 mm

• Hole diameter: 10.07 mm

• Poor localization: AV 0.15 mm

• IT12

Advanced geometry

• Tool diameter: 10 mm

• Hole diameter: 10.025 mm

• Improved localization: AV 0.045 mm

• IT9

TOOL MAKER’S TIP

Improve holeaccuracy with

advanced HSS drills

16

CLAMPING DRILLS

Straight shank

• Basic choice

Straight shank with aninclined flat

• For large diameters(between 6 - 20 mm)

• For oil-hole drills

• Prevents the drill fromslipping out of the chuck

Straight shank with atang

• For quick tool change

• Simple holder with highrigidity

• Large runout

Morse taper shankwith a tang

• For large diameters

• For quick tool change

• High rigidity

TOOL MAKER’S TIP

Drills are alsoavailable:

-with a reinforcedshank for higher

rigidity andsmall tools

-or with a smallershank for barturning lathes

17

THE BASICS OF DRILLING18

• Drilling is a machining operation in which the toolrotates with an axial displacement, except whenmounted on lathes, where the drill is fixed and thedrilled bars rotate.

• In drilling, the cutting speed varies along thecutting edge. At the drill point, the cutting speedis zero. The point does not cut, but pushes themetal.

TOOL MAKER’S TIP

Did you know? Thereare drilled holes

in 75% of allmechanical parts

TYPICAL CUTTING SPEEDS

0

Nickel alloys >850 Mpa (Feed No. 2)

Titanium alloys (type TA6V) (Feed No. 2)

Duplex / highly alloyed stainless steels (Feed No. 4)Nickel alloys < 850 Mpa (Feed No. 3)

Ferritic , martensitic , ferritic-austenitic stainless steels (Feed No. 4)Cu Al Fe (Feed No. 5)

Austenitic stainless steels (Feed No. 4)Hardened cast iron > 270 HB (Feed No. 4)

Thermosetting plastics (Feed No. 5)Steels 850 - 1200 Mpa (Feed No. 3)

Lamellar graphite cast iron (Feed No. 7)Pure Titanium (Feed No. 2)

Steels: 550 - 850 Mpa (Feed No. 5)Nodular graphite cast iron (Feed No. 7)

Cu Al Ni (Feed No. 4)Graphite (Feed No. 5)

Pure Nickel (Feed No. 4)Steels < 550 Mpa (Feed No. 6)

Aluminium Si > 10% (Feed No. 6)Magnesium (Feed No. 6)

Aluminium Si 5-10% (Feed No. 7)Plastics (Feed No. 5)

Pure copper (Feed No. 5)Copper alloys - short chips (Feed No. 5)

Cooper alloys - long chips (Feed No. 5)Aluminium Si <5% (Feed No. 7)

20 40 60 80 100 120 140 160 180 200

19

Uncoated HSSdrill

Coated HSSdrill

Coated PM-HSSdrill

Cutting speed in m/min

FEEDS20

2.00 0.020 0.025 0.032 0.040 0.050 0.063 0.080 0.100 0.1252.50 0.025 0.032 0.040 0.050 0.063 0.080 0.100 0.125 0.1603.15 0.032 0.040 0.050 0.063 0.080 0.100 0.125 0.160 0.1604.00 0.040 0.050 0.063 0.080 0.100 0.125 0.160 0.200 0.2005.00 0.040 0.050 0.063 0.080 0.100 0.125 0.160 0.200 0.2506.30 0.050 0.063 0.080 0.100 0.125 0.160 0.200 0.250 0.3158.00 0.063 0.080 0.100 0.125 0.160 0.200 0.250 0.315 0.315

10.00 0.080 0.100 0.125 0.160 0.200 0.250 0.315 0.400 0.40012.50 0.080 0.100 0.125 0.160 0.200 0.250 0.315 0.400 0.50016.00 0.100 0.125 0.160 0.200 0.250 0.315 0.400 0.500 0.63020.00 0.125 0.160 0.200 0.250 0.315 0.400 0.500 0.630 0.63025.00 0.160 0.200 0.250 0.315 0.400 0.500 0.630 0.800 0.80031.50 0.160 0.200 0.250 0.315 0.400 0.500 0.630 0.800 1.00040.00 0.200 0.250 0.315 0.400 0.500 0.630 0.800 1.000 1.25050.00 0.250 0.315 0.400 0.500 0.630 0.800 1.000 1.250 1.25063.00 0.315 0.400 0.500 0.630 0.800 1.000 1.250 1.600 1.60080.00 0.400 0.500 0.630 0.800 1.000 1.250 1.600 1.600 2.000

1 2 3 4 5 6 7 8 9

0.50 0.004 0.006 0.007 0.008 0.010 0.012 0.014 0.016 0.0191.00 0.006 0.008 0.012 0.014 0.016 0.018 0.020 0.023 0.025

F (mm/rev.)

Feed column No.Drill Ømm

COOLING AND CHIP REMOVAL

• Cutting fluids are essential for heat evacuation, chipremoval and for lubrication, to prevent adhesive wearat the drill point (where the cutting speed is zero).

• In drilling, soluble oils are usually preferred but oil canalso be used.

• Soluble oils with additives significantly prolong the toollife of HSS drills.

• The cutting fluid must be supplied directly to thecutting edge.

• The amount of lubricant required depends on drilldiameter, hole depth and cutting data.

TOOL MAKER’S TIP

Oil-hole drillsincrease tool life

21

Pressure and quantity

Coo

lant

pre

ssur

e (in

bar

s)

Coo

lant

qua

ntity

in I/

min

Drill Ø in mm

MAKE THE BEST USE OF OIL-HOLE DRILLS22

TOOL MAKER’S TIP

Oil-hole drills areessential for longer

tool life, higherspeeds and deep

holes

Benefits of oil-hole drills and high pressure coolant

+ prevent chip welding

+ prevent damaging chemical reactions that occur athigh temperatures

+ prolong tool life (up to 300%)

+ allow an increase of cutting speeds by more than 30%

+ improve surface finish

Oil hole

SUCCESS STORY

Operation • Drilling of holes Ø 8.25 mm, L 80 mm in an automotive part

Tool • HSS-PM 9% Co. Drill with oil holes + coating + special geometryCutting data • vc 60 m/min, f 0.25 mm/rev

Tool life • more than doubled compared with a carbide drill (812 holes insteadof 375 holes)

Costs per hole • divided by 2 compared with a carbide drill

Cast iron

HOW TO MONITOR WEAR

• Normal wearpattern

• Increase thecutting speed (vc)and/or the feed (fz)

• Increase theeffective cuttingangle

• To be avoided

• Decrease thecutting speed (vc)and/or the feed (fz)

• Use a coated tooland a harder HSSmaterial

• To be avoided

• Decrease thecutting speed (vc),increase thecoolant pressure

• Use a tougherHSS material

• To be avoided

• Decrease thecutting speed (vc)and/or the feed (fz)

• Use a coated tooland a harder HSSmaterial

• To be avoided

• Increase thecutting speed (vc)and/or the feed (fz)

• Use a coated tooland a harder HSSmaterial

23

Flank wear Crater wear Chipping Deformation Built-up edge

WHAT CHIPS HAVE TO SAY

• Long curly chips stick to the flute and prevent thecoolant from going through the hole. The result is toolmelting or breakage.

• When too short, chips are difficult to evacuate andsometimes pack in the flute. This worsens the qualityof the drilled hole and shortens tool life.

TOOL MAKER’S TIP

Short chips are proofthat the feed rate is

well chosen

24

Drilling chip shapes

Chip form at each stage of the drilling processwhen a drill with point thinning is used

SOLVE YOUR DRILLING PROBLEMS25

Problem

Oversize hole

Irregular hole size

Low position accuracy

Poor hole perpendicularity

Bad cylindrical accuracy

Poor surface finish

Drill breakage

Tang breakage

Solutions

Check holder and run-outRegrind and check precision

Check holder and run-outRegrind and check precisionDecrease feed rateUse an oil-hole drill

Check holder and run-out, checkalignment, select a low cutting resistancethinning, use a drill bush, or use centering

Regrind and check precision, check theworkpiece position, make a center hole

Regrind and check precision Check holder and run-outUse a large web drill

Regrind correctly, increase coolant volumeand improve quality, reduce feed rate,select a wide flute, high helix oil-hole drill

Increase rigidity, reduce feed rate, selecta wide flute, high helix oil-hole drill, use adrill bush or centering

Modify the surface of the holder orchange the holder

Causes

Loose hold, unequal point angle, varying length of lip

Loose hold, unequal point angle, large length of lip, excessive feed rate, poor lubrication

Spindle run outLow alignment accuracyRun out when cutting

Excessive tool wear, unequal point angle, drilling surface not horizontal, poor alignment (on lathes)

Unequal point angle, loose hold, relief angle too wide, low drill rigidity

Poor regrinding, cooling problem, loose hold, excessive feed rate, chip packing

Low rigidity, excessive feed rate, tool wear,chip packing, difficult entering

Slipping chuck, defect (damage, swarf)of the inner surface of morse taper

TIPS FOR SPECIAL DRILLING CONDITIONS

• Mill a flat surfacebefore drilling

• Make a pre-holewith a center orstarting drill

• Use a guide bush

• Use a highly rigiddrill

• Decrease the feedrate

• To be avoided

• Use a highly rigiddrill or a doublemargin drill

• Reduce the feedrate

• Fill the hole withthe same materialin order to balancethe cutting

• Use a back-upplate

• Use a brad pointor a step drill

• Reduce the feedrate

• Use a brad pointor a step drill

• Reduce the feedrate

• Use a brad pointor a step drill

• Use an end millinstead of a drill

26

Drilling ofinclined surface

Cross-hole andnon-symetric

hole

Drilling sheets Drilling stackedplates

Pipe drilling

USEFUL DRILLING FORMULAE27

Symbol Unit Name

D mm Tool diameter

I mm Hole depth

L mm Total run:approach run+ hole depth+ length of point

N rev/mm Revolution perminute

Symbol Unit Name Formulae

vc m/min Cutting speed

vf m/min Feed per minute

f mm/rev Feed per revolution

T min Machining time

vf =Nf

vf

vc= πDN1000

T= L fN

f= N