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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