ISO 7721通用头型沉头螺钉用沉孔

Countersinks for countersunk head screws with ISO 7721 common head style

Senkungen für Senkschrauben mit Einheitköpfen nach ISO 7721

In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker.

Dimensions in mm

1 Field of application

This standard specifies countersinks for medium series clearance holes as covered in ISO 273 which are designed to receive countersunk head screws with ISO 7721 common head style, as covered in ISO 1482, 1483, 2009, 2010, 7046, 7047, 7050, and 7051. For countersinks for other types of countersunk head screws, see DIN 74 Part 1.

Continued on pages 2 and 3

Beuth Verlag GmbH, Berlin, has the exclusive right of sale for German Standards (DIN-Normen).

1

2 Dimensions and designation

Designation of a size 4 countersink for an M4 countersunk head screw with common head style or a ST4,2 tapping screw:

Countersink DIN 66 – 4

Table 1.

Size		1,6	2	2,5	3	3,5	4	5	5,5
For	metric screws	M1,6	M2	M2,5	M3	M3,5	M4	M5	–
	tapping screws	–	ST2,2	–	ST2,9	ST3,5	ST4,2	ST4,8	ST5,5
Clearance hole, d1 H 13 (medium series)	Nominal size	1,8	2,4	2,9	3,4	3,9	4,5	5,5	6*)
	Limit deviations	+ 0,14 / 0	+ 0,14 / 0	+ 0,14 / 0	+ 0,18 / 0	+ 0,18 / 0	+ 0,18 / 0	+ 0,18 / 0	+ 0,18 / 0
d2	Nominal size	3,6	4,4	5,5	6,3	8,2	9,4	10,4	11,5
	Limit deviations	+ 0,1 / 0	+ 0,1 / 0	+ 0,1 / 0	+ 0,2 / 0	+ 0,2 / 0	+ 0,2 / 0	+ 0,25 / 0	+ 0,25 / 0
t	≈	0,95	1,05	1,35	1,55	2,25	2,55	2,58	2,88
*) Not included in ISO 273.

Size		6	8	10	12	14	16	18	20
For	metric screws	M6	M8	M10	M12	M14	M16	M18	M20
	tapping screws	ST6,3	ST8	ST9,5	–	–	–	–	–
Clearance hole, d1 H 13 (medium series)	Nominal size	6,6	9	11	13,5	15,5	17,5	20	22
	Limit deviations	+ 0,22 / 0	+ 0,22 / 0	+ 0,27 / 0	+ 0,27 / 0	+ 0,27 / 0	+ 0,27 / 0	+ 0,33 / 0	+ 0,33 / 0
d2	Nominal size	12,6	17,3	20	24	28	32	36	40
	Limit deviations	+ 0,25 / 0	+ 0,25 / 0	+ 0,3 / 0	+ 0,3 / 0	+ 0,3 / 0	+ 0,4 / 0	+ 0,4 / 0	+ 0,4 / 0
t	≈	3,13	4,28	4,65	5,4	6,4	7,45	8,2	9,2

2

3 Surface roughness

The ten-point-height of irregularities, R_z, of countersinks shall be 25.

4 Indications on drawings

4.1 Use of symbols (examples)

4.2 Indication of actual dimensions (example)

Standards referred to

DIN 74 Part 1	Countersinks for countersunk head screws
ISO 273	Fasteners; clearance holes for bolts and screws
ISO 1482	Slotted countersunk (flat) head tapping screws (common head style)
ISO 1483	Slotted raised countersunk (oval) head tapping screws (common head style)
ISO 2009	Slotted countersunk head screws (common head style); product grade A
ISO 2010	Slotted raised countersunk head screws (common head style); product grade A
ISO 7046	Cross recessed countersunk flat head screws (common head style); product grade A and property class 4.8 only
ISO 7047	Cross recessed raised countersunk head screws (common head style); product grade A
ISO 7050	Cross recessed countersunk (flat) head tapping screws (common head style)
ISO 7051	Cross recessed raised countersunk (oval) head tapping screws
ISO 7721	Countersunk head screws; head configuration and gauging

Explanatory notes

The Normenausschuß Mechanische Verbindungselemente (Fasteners Standards Committee) made the decision to adopt the ISO Standards on ISO 7721 common head style countersunk head screws as national standards. As a consequence, the mating countersinks had also to be specified. As a departure from DIN 74 Part 1, this standard covers both metric screws and tapping screws, most countersink dimensions remaining unchanged.

The countersink dimensions have been specified here so as to ensure that cases where the head diameter is a maximum and the countersink diameter, d₂, a minimum, the screw head is still flush with the workpiece surface.

Although the standard deals with countersinks for ISO 272 medium series clearance holes, it may also be applied, by analogy, to fine series clearance holes, since d₂ is not a function of the clearance hole diameter. Thus, a differentiation between both series need not be made in the designation.

International Patent Classification

F 16 B 5/02

3

Table 3. Lightweight horizontally perforated brick panels, dimensions

Column	1	2	3	4	5
Line	Dimensions	Work size	Minimum limit of size	Maximum limit of size	Dimensional range t
1	Length l	330	317	333	12
2		495	480	500	15
3		995	975	1000	18
4	Height h	175	168	178	8
5		238	230	245	10
6		320	310	328	12
7	Thickness s	40	38	42	3
8		50	48	52	3
9		60	57	63	4
10		70	67	73	4
11		80	76	84	5
12		100	96	104	5
		115	100	120	6

Figure 5. Lightweight horizontally perforated brick panel

Table 4. Apparent brick density

Apparent brick density class	Mean apparent brick density1) kg/dm3
0,5	0,41 to 0,50
0,6	0,51 to 0,60
0,7	0,61 to 0,70
0,8	0,71 to 0,80
0,9	0,81 to 0,90
1,0	0,91 to 1,00
1) Individual values shall not exceed or fall below the limits by more than 0,05 kg/dm3.

3.6 Compressive strength

The compressive strength classes specified in table 5 shall apply for lightweight horizontally perforated bricks. The actual values shall not fall below either the mean values or the minimum individual values.

Table 5. Compressive strength

Column	1	2		3
Line	Compressive strength class	Mean value	Lowest individual value
1	2	2,5	2,0
2	4	5,0	4,0
3	6	7,5	6,0
4	12	15,0	12,0

3.7 Bending strength of lightweight horizontally perforated brick panels

In the bending test specified in subclause 6.4, the lightweight horizontally perforated brick panels shall withstand a bending load of 500 N (minimum permissible individual value 400 N).

3.8 Harmful, expansive particles content

Lightweight horizontally perforated bricks and lightweight horizontally perforated brick panels shall be free from expansive particles, e.g. lime. If bricks contain expansive particles liable to diminish their usability, the test described in subclause 6.5 (water vapour test) shall be carried out.

Bricks shall be deemed to have passed the test if they exhibit no structural damage or if not more than 5 chips with a maximum depth of 3 mm occur for every 100 cm² of external face.

If the result of testing does not allow a definite assessment to be made, a comparative compressive test as specified in subclause 6.3 shall be carried out. The bricks

4

3.9 Content of harmful salts causing efflorescence

Bricks shall be free from harmful salts leading to structural damage in the bricks or plaster. Bricks shall be deemed to have passed the test for harmful salts if the test described in subclause 6.5, carried out on loose bricks, shows that the proportion by mass of magnesium sulfate (MgSO4) does not exceed 0,12 %.

4 Designation

The following symbols shall be used for the various types of brick:

LLz lightweight horizontally perforated brick

LLp lightweight horizontally perforated brick panel

The sequence of elements used when designating lightweight horizontally perforated bricks shall be term, DIN number, type of brick (symbol), compressive strength class, apparent brick density class and format symbol as given in table 6.

Example of designation:

Designation of a lightweight horizontally perforated brick (LLz) of compressive strength class 12, apparent brick density class 0,9, length l = 240 mm, width b = 175 mm and height h = 113 mm (3 DF):

Brick DIN 105 — LLz 12 — 0,9 — 3 DF

The sequence of elements used when designating lightweight horizontally perforated brick panels shall be DIN number, type of brick (symbol), apparent brick density class and format symbol as given in table 7.

Example of designation:

Designation of a lightweight horizontally perforated brick panel (LLp) of apparent brick density class 0,6, length l = 330 mm, height h = 238 mm and thickness s = 80 mm (80 s):

Brick DIN 105 — LLp 0,6 — 80 s

If lightweight horizontally perforated brick panels are produced with differing length or height, these dimensions shall also be stated in the designation.

Example of designation:

Designation of a lightweight horizontally perforated brick panel (LLp) of apparent brick density class 0,6, length l = 495 mm, height h = 320 mm and thickness s = 60 mm:

Brick DIN 105 — LLp 0,6 — 495 × 320 × 60

5 Marking

All bricks shall be provided with a works mark (manufacturer's mark) and the symbol identifying the brick type (LLz or LLp).

Lightweight horizontally perforated bricks ready for dispatch shall additionally be marked on one stretcher face with a colour coding stripe not less than 20 mm in width, indicating the compressive strength class (see table 8) and details of their apparent brick density class.

An indication of the apparent density class is considered adequate for lightweight horizontally perforated brick panels.

It shall be deemed sufficient if one brick is marked for up to 200 lightweight horizontally perforated bricks not less than 10 DF and for up to 50 lightweight horizontally perforated brick panels.

Table 6. Lightweight horizontally perforated bricks, format symbols (examples)

Format symbol DF (thin format)	Dimensions
	l	b	h
NF	240	115	71
2 DF	240	115	113
3 DF	240	175	113
8 DF	240	240	238
12 DF	365	240	238
16 DF	490	240	238
10 DF	240	300	238
15 DF	365	300	238
20 DF	490	300	238

Table 7. Lightweight horizontally perforated brick panels, format symbols (examples)

Format symbols	Dimensions
	l	h	s
40 s	330	238	40
50 s	330	238	50
60 s	330	238	60
70 s	330	238	70
80 s	330	238	80
100 s	330	238	100
115 s	330	238	115

Table 8. Colour coding

Compressive strength class	Colour
2	Green
4	Blue
6	Red
12	No marking

5

6 Testing

6.1 Shape, dimensions, perforation

In accordance with DIN 105 Part 1.

A measuring rule or a gauge board with a millimetre scale is sufficient for measuring the length of lightweight horizontally perforated brick panels with dimensions exceeding 495 mm.

The deflection shall also be determined for lightweight horizontally perforated brick panels as illustrated in figure 5. In this determination, the panel shall be pressed on a longitudinal face or width against a smooth surface. Deviations from straightness shall be determined using a measuring wedge and stated to the nearest whole millimetre.

6.2 Apparent brick density

In accordance with DIN 105 Part 1.

6.3 Compressive strength

In accordance with DIN 105 Part 1.

Lightweight horizontally perforated bricks, including standard format bricks, shall be tested as whole bricks. Form factors shall not be applied.

6.4 Bending strength

The bending strength of lightweight horizontally perforated brick panels shall be determined on 5 air-dried samples.

Each panel shall be tested lying flat. The panel shall be placed on two supports so that it can move and stressed in the middle parallel to the supports by means of a 20 mm wide mandrel. The distance between supports shall equal the length of the panel minus 50 mm. The load shall be increased steadily at a rate of approximately 10 N per second.

6.5 Expansive particles and water-soluble salts

In accordance with DIN 105 Part 1.

7 Inspection

7.1 General

See DIN 105 Part 1.

7.2 Internal control

In accordance with DIN 105 Part 1.

7.3 Third party inspection

In accordance with DIN 105 Part 1.

The inspection of lightweight horizontally perforated brick panels shall include the bending strength test instead of the compressive strength test and the determination of deflection.

8 Delivery note

In accordance with DIN 105 Part 1.

Standards referred to

DIN 105 Part 1 Clay bricks; solid bricks and vertically perforated bricks

International Patent Classification

E 04 C 1-00

6