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DIN 7984 Specifications

DIN 7984 Specifications – Hex Socket Head Cap Screws with Low Head

Core Technical Specifications Summary of DIN 7984

1. Scope of Application & Core Characteristics

  • Product: Hexagon socket low head cap screws.

  • Standard: DIN 7984 (February 1998 edition, replacing the May 1985 edition).

  • Thread Range: M3 to M24, product grade A.

  • Key Interchangeability: Its head dimensions are interchangeable with DIN 84 (Cap screws), facilitating design substitution.

  • Important Caution: The standard explicitly states that due to its head design and hexagon socket structure, its axial load-bearing capacity is limited. It is not recommended for applications requiring high preload and must not be used in conjunction with DIN 6900 combined washers.

2. Core Dimensional Specifications

  • Key Dimensions (Summary from tables):

    • Head Diameter (d_k): e.g., the max head diameter for an M6 screw is 10.5mm.

    • Head Height (k): e.g., the nominal head height for an M6 screw is 5mm.

    • Wrench Size (s): e.g., the hexagon key size for an M6 screw is 4mm.

    • Nominal Length (l): Covers a wide range from very short (5mm) to over 100mm (increasing in 10mm increments for lengths >100mm).

  • Thread Length Rules: The standard defines calculation rules for l_s (minimum length of unthreaded shank) and l_g (maximum length of threaded portion), which are crucial for determining the clamping area.

3. Materials & Mechanical Properties

  • Default Materials & Grades:

    • Steel: Default property class is 8.8 (conforming to DIN ISO 898-1). Other grades require agreement.

    • Stainless Steel: For screws ≤ M20, commonly A2-70; for screws > M20, commonly A2-50 (conforming to DIN 267-11).

    • Non-Ferrous Metals: e.g., brass.

  • Tolerances: Product grade A (conforming to DIN ISO 4759-1). Thread tolerance is typically 6g.

  • Surface Treatment: Steel screws are typically blackened (chemically or thermally). Stainless steel and non-ferrous metal screws have a bright finish. Other coatings (e.g., electroplating) require agreement upon ordering.

4. Testing, Technical Details & Marking

  • Special Testing Requirements: For property class 8.8 screws, hardness testing is a mandatory acceptance criterion (e.g., hardness for screws ≤ M16 must be between HV 250-320).

  • Weight Reference: The DIN 7984 weight chart page provides a detailed theoretical weight table (unit: grams) for logistics and cost calculation reference.

  • Product Marking Example:

    • A screw of size M12x60, property class 8.8, should be marked as:
      ** DIN 7984 – M12 × 60 – 8.8**

5. Key Referenced Standards

This standard references several key foundational standards, including:

  • Threads: DIN 13 series

  • Mechanical Properties: DIN ISO 898-1 (steel), DIN 267-11 (stainless steel)

  • Tolerances: DIN ISO 4759-1

  • Technical Delivery Conditions: DIN 267 series

Summary: The core advantage of the DIN 7984 screw is its low-profile head design and interchangeability with DIN 84. However, its most significant limitation is its low axial load-bearing capacity. During selection, it is essential to first evaluate whether its mechanical properties meet the specific application requirements, especially in scenarios involving preload.

 

DIN 7984 Specification

Thread Size M3 M4 M5 M6 M8 M10 M12
d
P Pitch 0.5 0.7 0.8 1 1.25 1.5 1.75
Length of Thread L≤125 12 14 16 18 22 26 30
b 125＜L≤200 / / / / 28 32 36
L＞200 / / / / / / /
dk max=nominal size 5.5 7 8.5 10 13 16 18
min 5.32 6.78 8.28 9.78 12.73 15.73 17.73
ds max=nominal size 3 4 5 6 8 10 12
min 2.86 3.82 4.82 5.82 7.78 9.78 11.73
k max=nominal size 2 2.8 3.5 4 5 6 7
min 1.86 2.66 3.32 3.82 4.82 5.82 6.78
s Nominal Size 2 2.5 3 4 5 7 8
max 2.1 2.6 3.1 4.12 5.14 7.175 8.175
min 2.02 2.52 3.02 4.02 5.02 7.025 8.025
t Nominal Size 1.5 2.3 2.7 3 3.8 4.5 5
max 1.62 2.42 2.82 3.12 3.95 4.65 5.15
min 1.38 2.18 2.58 2.88 3.65 4.35 4.85
e min 2.3 2.87 3.44 4.58 5.72 8.01 9.15

DIN 7984 Specification

Thread Size (M14) M16 (M18) M20 (M22) M24
d
P Pitch 2 2 2.5 2.5 2.5 3
Length of Thread L≤125 34 38 42 46 50 54
b 125＜L≤200 40 44 48 52 56 60
L＞200 / 57 61 65 69 73
dk max=nominal size 21 24 27 30 33 36
min 20.67 23.67 26.67 29.67 32.61 35.61
ds max=nominal size 14 16 18 20 22 24
min 13.73 15.73 17.73 19.67 21.67 23.67
k max=nominal size 8 9 10 11 12 13
min 7.78 8.78 9.78 10.73 11.73 12.73
s Nominal Size 10 12 12 14 14 17
max 10.175 12.212 12.212 14.212 14.212 17.23
min 10.025 12.032 12.032 14.032 14.032 17.05
t Nominal Size 5.3 5.5 6.5 7.5 8 8
max 5.45 5.65 6.68 7.68 8.18 8.18
min 5.15 5.35 6.32 7.32 7.82 7.82

e

 min 11.43 13.72 13.72 16 16 19.44

 

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