T h i n k s a f e t y , T h i n k H S S

TAPPING

TAPPING

TAPPING TOOLS2 Zoom on a tap

3 Which HSS for maximum efficiency?

4 Surface treatments for the best performance

5 Vocabulary

6 Tapping

7 Thread forming

8 Thread milling

9 Chamfer forms

10 Chamfer length

11 Tap size and thread size

12 Basic thread forms

13 Clamping taps

TAPPING PROCESS14 The basics of tapping

15 Typical cutting speeds

16 Cooling

17 Problem solving

18 Wear

1

SU

MM

AR

Y

ZOOM ON A TAP2

Type of flute

Chamfer form and length

Dimensions

Tool material

Coating

Clamping

WHICH HSS FOR MAXIMUM EFFICIENCY ?3

TOOL MAKER’S TIP

Reach the highestperformance with

HSS-PM taps

• Mainly for handtaps

• Basic choice • For higher cuttingspeeds andincreasedproductivity

• For higherperformance andlonger tool life

• For nickel alloys,titanium alloys andhard steels

HSS HSS-E5% cobalt

or high vanadium

HSS-E8% cobalt

HSS-PM

SURFACE TREATMENTS FOR THE BEST PERFORMANCE

TOOL MAKER’S TIP

For maximum coating efficiency, prefer a HSS-PM

substrate

4

• Basic choice• For a lower friction

coefficientSteam oxide

• For high speed tapping• For dry tapping

• For cast iron, siliconalloys, and thermosettingplasticsNitride

• Good anti-weldingproperties, reduces friction

• Used in combination withother coatings

• Suitable for dry machining

• Basic choice• For mild steels,

hard steels, tool steelsand hardened steels

• For dry tapping• For hard steels,

tool steels and hardened steels

TiNGold

TiCNGrey-violet

TiAlN orTiAlCN

Black-violet

MoS2 or WC-CGrey-black

CrNMetal

• For copper alloys, brass,bronze etc.

VOCABULARY

A TAP AROUND THEWORLD

French: un taraud

German: einGewindebohrer

Italian: un maschio

Spanish: un machode roscar

5

Flute

Web diameter

(Female) Center

(Male) Center

Chamfer length

Chamfer length

Thread length

Thread length

Overall length

Overall length

Square length

Square length

Square

widt

h

Square

widt

h

Sha

nkdi

amet

er

Sha

nkdi

amet

er

Land width

TAPPING6

Straight flutedtap with spiralpoint

• For through holes

• Removes the chipsin the cuttingdirection

Left hand spiralfluted tap

• For through holes

• Removes the chipsin the cuttingdirection

Straight flutedtap with longchamfer lead

• For through holes

Straight flutedtap with shortchamfer lead

• For blind holes

• For generalpurpose

• Chamfer leadlength calculatedto prevent chipsfrom jammingduring the returnmovement. Chipsare sheared offclearly

Right hand spiralfluted tap

• For blind holes

• Removes the chipsup the flutes

THREAD FORMING7

Fluteless taps produce internal threads without chipremoval. Fluteless taps are recommended for non ferrousmetals such as aluminum and cooper alloys, soft brassand soft steels.

Advantages:

• no chips• no cutting errors• no pitch errors• higher tensile strength• better surface finish• long tool life• high cutting speeds (double that of tapping)

For deep holes, fluteless taps with oil grooves arerecommended.

A-A section: different polygonal shapes

Crestforming

SUCCESS STORY

Operation • Tapping of holes M8x1.25 mm, height 9.7 mm

Problem • Too long swarf, requiring constant removal by operator and checkingeach thread for chip fragments

Solution • TiN coated HSS fluteless tap, without oil grooves

Benefits • Tool life x 20, i.e. 5000 threads (vs. 250 with former tap)

Boron alloyed Steel

800 N/mm2

THREAD MILLING8

Thread milling cutters produce internal threads by helicalinterpolation: the tool moves with axial (rotation) andorbital (revolution) motions, requiring simultaneous 3-axiscontrol and high machine and tool rigidity.

Advantages:

• For large hole diameters

• Only one tool needed to produce threads for differentnominal diameters

• Fine chips, preventing clogging

• Internal threading over the length of blind holes

• No stop marks

CHAMFER FORMS9

TOOL MAKER’S TIP

In tapping, all themachining is carried

out by the cuttingteeth of the chamfer

Form A

• Long

• 6-8 threads

• For short throughholes

• Increases thetorque and thusthe danger ofbreakage

Form B

• Medium

• 3.5-5 threads

• With spiral point,useful for blindholes

• For all throughholes and deeptapping holes

• Efficient in toughand tough hardmaterials

Form C

• Short

• 2-3 threads

• For blind holes

• Generally foraluminum, greycast iron and brass

Form D

• Medium

• 3.5-5 threads

• For through andblind holes withsufficient run-out

Form E

• Extremely short

• 1.5-2 threads

• For blind holeswith little run-outdepth

• Avoid use ifpossible

CHAMFER LENGTH10

Chamfer

N°1 lip N°5 lip N°9 lip

Complete thread

First taper tap

Second tap

Bottoming tap

Chip section area of the lastlip in the chamfer

Chip section area of the thirdlip in the chamfer

Chip section area of thesecond lip in the chamferChip section area of the firstlip in the chamfer

Tapping process with a four-flute tap andfive-thread chamfer

Chamfer lead length for sets of three taps

TAP SIZE AND THREAD SIZE

TOOL MAKER’S TIP

In most cases, after tapping,

the internal threadsize is larger than the

tap size

11

D min = Min. major diameter

D2 max = Max. pitch diameter

D2 min = Min. pitch diameter

D1 max = Max. minor diameter

D1 min = Min. minor diameter

d = Major diameter

d2 = Pitch diameter

d1 = Minor diameter

P = Pitch

α = Thread angle

INTERNAL THREAD

Dm

in

D2

max

P

α

D2

min

D1

max

D1

min

d 1

d 2

d

BASIC THREAD FORMS12

Metric thread ISO R68 (DIN13)

Whitworth thread BS 84

British StandardWhitworth

British StandardBUTTRESS

British StandardPipe Tap & ISO Taper Pipe

British StandardCYCLE

British Association

British & AmericanStandard GENERALPURPOSE ACME

TRAPEZOIDAL

American StandardPipe Taper

American StandardSTUB ACME

American StandardPIPE STRAIGHT

American StandardBUTTRESS

BUTTRESS(Continental)

Metric (S.I.)

ISO MetricISO Inch Unified

American StandardPipe TaperDRYSEAL NPTF

CLAMPING TAPS13

Square shank(with solid cone)

Square shank(with chamfer)

Square shank(with internal hole)

Weldon shank(with clamping flat)Seldom used

THE BASICS OF TAPPING14

Tapping is a machining operation which produces internalthreads in a drilled hole.

Tapping is the most efficient way to produce preciseinternal threads with cost efficiency.

Tapping is an easy operation but subject to chip packingin deep blind holes.

Tapping can be performed on all types of machines orwith a self-reversing tap holder.

TYPICAL CUTTING SPEEDS15

0

Nickel alloys >850 Mpa

Nickel alloys < 850 Mpa

Duplex / highly alloyed stainless steelsTitanium alloys (type TA6V)

Ferritic , martensitic , ferritic-austenitic stainless steelsCu Al Fe

Steels 850 - 1200 MpaAustenitic stainless steels

Hardened cast iron > 270 HBSteels: 550 - 850 Mpa

Pure NickelNodular graphite cast iron

Pure TitaniumThermosetting plastics

Pure copperAluminium Si > 10%

Steels < 550 MpaGraphite

Lamellar graphite cast ironCooper alloys - long chips

Cu Al NiPlastics

Aluminium Si 5-10%Copper alloys - short chips

Aluminium Si <5%Magnesium

20 40 60 80 100 120 140 160 180 200

Uncoated HSStap

Coated HSStap

Coated PM-HSStap

Cutting speed in m/min

COOLING16

SUCCESS STORY - Dry tapping in…

Operation • Through hole tapping of a hole 1.6 x dia., without coolant

Tool • HSS Co5 + TiCN coating tap with special geometry

Benefits • High speed tapping vc 50 m/min (vs. 15-20 m/min with 5% emulsion)

• Long tool life of approx. 900 holes, 10 times longer than without coating

• Increased productivity plus environmental benefits from dry tapping

Carbon steel C45, 650 N/mm2

Cutting fluids in tapping

Lubricating, cooling and chip removal are essential in thetapping operation because the cutting speed is slowand chips tend to pack.

In tapping, oils are usually preferred but highperformance soluble oils are increasingly used.

Oil-hole taps

Oil-hole taps are recommended for high performancetapping or for difficult-to-machine materials.

Dry tapping

Tapping with micro-lubrication is also possible.

Radial coolant duct exit

Axialcoolantduct exit

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PROBLEM SOLVING17

Select a tap with tighter thread tolerance or with a longer chamfer length. Avoid tap deflection.Use a tap with a spiral flute. Decrease the speed. Use a coated tap to prevent edge built-up.Increase coolant flow.

Solutions

Use an oversized tap, when machining copper, aluminium alloys and cast iron or when tappingthin plates, or if meeting holes. Increase the speed. Decrease the speed during the return motion.Increase coolant flow.

Undersizedinternal thread

Select a tap with a longer chamfer length. Use a coated tap and increase coolant flow.Reduce the cutting speed. Use a tap with a spiral flute. Prevent excessive cutting torque byenlarging the hole before tapping.

Use a more rigid tap holder and piece clamping. Increase coolant flow or use a high qualitycoolant.

Galling and torninternal thread

Rough surface ofinternal thread

Use a tap with a spiral flute. Prevent excessive cutting torque by enlarging the hole beforetapping. Reduce the cutting speed. Prevent the tap from colliding with the bottom of the hole.

Breakage of tap

Select a tap with a longer chamfer length. Use a tap with a spiral flute. Reduce the cutting speed. Use a high quality coolant.

Chipping of tapthread

Use a coated tap. Select a tap with a longer chamfer length. Reduce the cutting speed. Use a high quality coolant.Early tap wear

Increase coolant flow. Adjust the cutting speed. Use a coated tap.Welding on the tap

Problem

Oversizedinternal thread

WEAR18

WearChipping

Galling Torn thread