Blind hole tap – Aluminium and light alloys

45° right-hand spiral flute tap for blind holes in aluminium and light alloys: the chip flows back towards the shank. Bright, 20 – 25° rake.

ISO N

Blind holes

45° helix

Bright

M2 – M36

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Geometry by material

Chamfer, helix and rake chosen for the material

DIN 371 / 376 sizes

Metric, fine, pipe and inch, also custom made

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Description

Technical drawing

At a glance

Hole type	Blind holes
Geometry	Right-hand helix 45° · 3 spiral flutes
Chamfer	Form C, 2 – 3 threads
Chip	Flows back along the helix towards the shank: the bottom of the hole stays clean
Thread depth	Up to 2 × d
Rake angle	20 – 25°
Tool material	HSS-E
Coating	bright (first choice) · alternatively CrN, DLC
Tolerance	6H; 6G and 7G for threads to be galvanised or painted
Design	Reinforced shank from M2 to M10 (DIN 371), reduced shank from M12 (DIN 376); from M3 to M10 also with reduced shank for deep holes
Cutting direction	Right-hand; left-hand on request

Workpiece materials

Group	Aluminium and light alloysISO N
Strength	up to 600 N/mm²
Examples	EN AW-6082, 6061, 7075, 2011, 5083 and casting alloys with Si up to 10 %

Sizes – ISO metric thread

Thread	Pitch P	Tap drill Ø	L overall	l thread	Ø d2 shank	Square a
M2	0,4	1,6	45	8	2,8	2,1
M2,5	0,45	2,05	50	9	2,8	2,1
M3	0,5	2,5	56	7	3,5	2,7
M3,5	0,6	2,9	56	7	4	3
M4	0,7	3,3	63	8	4,5	3,4
M5	0,8	4,2	70	10	6	4,9
M6	1	5	80	12	6	4,9
M8	1,25	6,8	90	16	8	6,2
M10	1,5	8,5	100	16	10	8
M12	1,75	10,2	110	18	9	7
M14	2	12	110	20	11	9
M16	2	14	110	22	12	9
M18	2,5	15,5	125	25	14	11
M20	2,5	17,5	140	25	16	12
M22	2,5	19,5	140	25	18	14,5
M24	3	21	160	30	18	14,5
M27	3	24	160	30	20	16
M30	3,5	26,5	180	35	22	18
M33	3,5	29,5	180	35	25	20
M36	4	32	200	45	28	22

Dimensions in mm. M39 to M100 and fine, pipe and inch threads on request. The tap drill Ø is the one recommended for tolerance 6H. In blind holes the thread length is shorter to leave room for the chip in the helix.

Coatings for aluminium and light alloys

Coating	When to choose it
Bright (uncoated) ★	The sharpest possible cutting edge: aluminium, copper and soft materials that do not tolerate rounded edges.
CrN – chromium nitride	Anti-sticking surface: aluminium, copper, brass and titanium, where the chip tends to weld onto the thread.
DLC – amorphous carbon (diamond-like)	Very low friction and no built-up edge: aluminium alloys, copper and engineering plastics in high-volume production.

★ INNOT first choice for this material. Every tap can be supplied with any coating in the range: specify it in your request.

Starting data

Printable cutting data tableAll the data on this page in an INNOT PDF to keep in the shop.Download PDF

Cutting speed Vc	12 – 25 m/min (lower value for uncoated substrate or machines with a compensating chuck)
Feed	Equal to the thread pitch: synchronised tapping or chuck with axial compensation
Lubrication	Plenty of emulsion or oil; never dry

Thread	Spindle speed (n)
M6	640 – 1.330
M10	380 – 800
M16	240 – 500
M24	160 – 330

Guide values to be adapted to machine, clamping and lubrication. n = Vc × 1000 / (π × d).

Tips for use

Drill at least 3 pitches deeper than the thread: the tap must never touch the bottom of the hole.
The chip flows back along the helix: beyond 1.5 × d depth you need plenty of coolant or internal coolant (on request).
Set a smooth reversal at the end of the stroke: abrupt reversals chip the cutting edge.
Avoid lean emulsions: aluminium welds onto the thread. With high-silicon alloys (over 10 %) use the cast iron tap.
Chamfer the hole entry at 90°: clean start and no burr on the first thread.

Selection guide

Material

Through holes

Blind holes

Structural and annealed steelsup to 800 N/mm²

Spiral pointTiN 35° helixTiN

Quenched and tempered and alloy steels800 – 1400 N/mm²

Spiral pointTiCN 40° helixTiCN

Stainless steels450 – 1000 N/mm²

Spiral pointsteam oxide 35° – 40° helixsteam oxide

Cast irons and short chipsup to 300 HB

Straight flutesTiCN

Aluminium and light alloysSi up to 10 %

Spiral pointbright 45° helixbright

↻

Chiplesssteels, stainless steels, aluminium

Forming tapTiN · steam oxide · CrN

Fine, pipe, inch and left-hand threads: special and custom threads.

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