DIN 127 spring washers
DIN 127 spring washers cover 18 standardized diameters from M1.6 to M39, with section thicknesses ranging from 0.3 mm / 0.012 in to 7.0 mm / 0.276 in. Designed as open rings with rectangular section and offset ends, they generate an elastic force that prevents loosening in bolted joints subjected to vibration.
Dimensions
Section titled “Dimensions”The main dimensions of the DIN 127 washer are the inner diameter (d₁), outer diameter (d₂), and thickness (s). The following table lists the standardized values for form B (flat ends), the most common in industry.
| Nominal bolt diameter | d₁ (mm / in) | d₂ (mm / in) | s (mm / in) | Approx. weight per 1000 pcs (kg / lb) |
|---|---|---|---|---|
| M1.6 | 1,7 / 0.067 | 3,6 / 0.142 | 0,4 / 0.016 | 0,030 / 0.066 |
| M2 | 2,1 / 0.083 | 4,4 / 0.173 | 0,6 / 0.024 | 0,058 / 0.128 |
| M2.5 | 2,6 / 0.102 | 5,1 / 0.201 | 0,7 / 0.028 | 0,080 / 0.176 |
| M3 | 3,1 / 0.122 | 5,9 / 0.232 | 0,8 / 0.031 | 0,117 / 0.258 |
| M3.5 | 3,6 / 0.142 | 7,1 / 0.280 | 0,9 / 0.035 | 0,180 / 0.397 |
| M4 | 4,1 / 0.161 | 7,6 / 0.299 | 1,0 / 0.039 | 0,224 / 0.494 |
| M5 | 5,1 / 0.201 | 9,2 / 0.362 | 1,2 / 0.047 | 0,347 / 0.765 |
| M6 | 6,1 / 0.240 | 11,8 / 0.465 | 1,6 / 0.063 | 0,675 / 1.488 |
| M8 | 8,1 / 0.319 | 14,8 / 0.583 | 2,0 / 0.079 | 1,030 / 2.271 |
| M10 | 10,2 / 0.402 | 18,1 / 0.713 | 2,5 / 0.098 | 1,640 / 3.616 |
| M12 | 12,2 / 0.480 | 21,1 / 0.831 | 3,0 / 0.118 | 2,650 / 5.843 |
| M14 | 14,2 / 0.559 | 24,1 / 0.949 | 3,2 / 0.126 | 3,480 / 7.672 |
| M16 | 16,2 / 0.638 | 27,4 / 1.079 | 3,5 / 0.138 | 4,950 / 10.91 |
| M18 | 18,2 / 0.717 | 29,4 / 1.157 | 4,0 / 0.157 | 6,450 / 14.22 |
| M20 | 20,2 / 0.795 | 33,6 / 1.323 | 4,5 / 0.177 | 8,820 / 19.44 |
| M22 | 22,5 / 0.886 | 35,9 / 1.413 | 5,0 / 0.197 | 10,4 / 22.93 |
| M24 | 24,5 / 0.965 | 40,0 / 1.575 | 5,0 / 0.197 | 14,3 / 31.53 |
| M27 | 27,5 / 1.083 | 43,0 / 1.693 | 5,6 / 0.220 | 18,2 / 40.12 |
| M30 | 30,5 / 1.201 | 48,2 / 1.898 | 6,0 / 0.236 | 23,5 / 51.81 |
| M36 | 36,5 / 1.437 | 56,0 / 2.205 | 7,0 / 0.276 | 35,2 / 77.60 |
| M39 | 39,5 / 1.555 | 60,0 / 2.362 | 7,0 / 0.276 | 39,8 / 87.74 |
Materials and finishes
Section titled “Materials and finishes”The most common base material is C67S spring steel (1.1231), hardened and tempered to achieve a surface hardness of 42 to 50 HRC. For corrosive environments, A2 stainless steel (1.4301) or A4 (1.4401) is used, with hardness in the range 250‑350 HV. Surface finishes include electrolytic zinc plating (Fe/Zn 8), zinc dichromate, nickel plating, and phosphating; in parentheses, stainless steel washers are supplied uncoated or with passivation.
Mechanical properties
Section titled “Mechanical properties”The elastic capacity of the DIN 127 washer is guaranteed by a high-strength steel with minimum yield strength Rp0.2 ≥ 1250 MPa / 181 ksi. The compression test according to DIN 267‑26 requires that after being compressed to 75% of its initial free height, the washer shows no appreciable permanent deformation. Typical hardness values are summarized in the following table.
| Material | Hardness HRC (HV) | Tensile strength Rm (MPa / ksi) |
|---|---|---|
| Spring steel C67S | 42 – 50 HRC (412 – 509 HV) | 1300 – 1700 / 188 – 246 |
| Stainless steel A2 | 25 – 35 HRC (255 – 335 HV) | 700 – 900 / 101 – 130 |
Recommended tightening torques
Section titled “Recommended tightening torques”The recommended torque values correspond to metric bolts with standard thread pitch in class 8.8 (lubricated and dry), assembled with DIN 127 washer. It is recommended to replace the washer each time the joint is disassembled.
| Thread | Pitch (mm / in) | Dry tightening torque (Nm / ft·lb) | Lubricated tightening torque (Nm / ft·lb) |
|---|---|---|---|
| M3 | 0,5 / 0.020 | 1,2 / 0.89 | 0,9 / 0.66 |
| M4 | 0,7 / 0.028 | 2,8 / 2.07 | 2,1 / 1.55 |
| M5 | 0,8 / 0.031 | 5,5 / 4.06 | 4,1 / 3.02 |
| M6 | 1,0 / 0.039 | 9,5 / 7.01 | 7,1 / 5.24 |
| M8 | 1,25 / 0.049 | 23,0 / 16.96 | 17,0 / 12.54 |
| M10 | 1,5 / 0.059 | 46,0 / 33.93 | 34,0 / 25.08 |
| M12 | 1,75 / 0.069 | 80,0 / 59.00 | 60,0 / 44.25 |
| M14 | 2,0 / 0.079 | 125 / 92.2 | 95,0 / 70.1 |
| M16 | 2,0 / 0.079 | 195 / 143.8 | 145 / 106.9 |
| M20 | 2,5 / 0.098 | 380 / 280.2 | 280 / 206.5 |
| M24 | 3,0 / 0.118 | 660 / 486.8 | 500 / 368.8 |
| M30 | 3,5 / 0.138 | 1300 / 958.8 | 980 / 722.8 |
Drill sizes for corresponding bolts
Section titled “Drill sizes for corresponding bolts”For assembly with DIN 127 washer, clearance holes are used. The following table indicates the recommended drill sizes for clearance hole and for ISO coarse metric thread.
| Thread | Clearance drill (mm / in) | Tap drill (mm / in) |
|---|---|---|
| M3 | 3,4 / 0.134 | 2,5 / 0.098 |
| M4 | 4,5 / 0.177 | 3,3 / 0.130 |
| M5 | 5,5 / 0.216 | 4,2 / 0.165 |
| M6 | 6,6 / 0.260 | 5,0 / 0.197 |
| M8 | 9,0 / 0.354 | 6,8 / 0.268 |
| M10 | 12,0 / 0.472 | 8,5 / 0.334 |
| M12 | 14,0 / 0.551 | 10,2 / 0.402 |
| M14 | 16,0 / 0.630 | 12,0 / 0.472 |
| M16 | 18,0 / 0.709 | 14,0 / 0.551 |
| M20 | 22,0 / 0.866 | 17,5 / 0.689 |
| M24 | 27,0 / 1.063 | 21,0 / 0.827 |
| M30 | 33,0 / 1.299 | 26,5 / 1.043 |
Allowable loads
Section titled “Allowable loads”The maximum recommended clamping force is limited to 75% of the proof load of the bolt, thus ensuring that the washer works within the elastic range. Values for class 8.8:
| Thread | Tensile stress area (mm² / in²) | Proof load (kN / kip) | Max. clamping force (kN / kip) |
|---|---|---|---|
| M3 | 5,03 / 0.0078 | 3,02 / 0.679 | 2,26 / 0.508 |
| M4 | 8,78 / 0.0136 | 5,27 / 1.18 | 3,95 / 0.888 |
| M5 | 14,2 / 0.0220 | 8,52 / 1.92 | 6,39 / 1.44 |
| M6 | 20,1 / 0.0312 | 12,1 / 2.72 | 9,05 / 2.03 |
| M8 | 36,6 / 0.0567 | 22,0 / 4.94 | 16,5 / 3.71 |
| M10 | 58,0 / 0.0899 | 34,8 / 7.82 | 26,1 / 5.87 |
| M12 | 84,3 / 0.1307 | 50,6 / 11.4 | 37,9 / 8.53 |
| M14 | 115 / 0.1783 | 69,0 / 15.5 | 52,0 / 11.7 |
| M16 | 157 / 0.2434 | 94,2 / 21.2 | 70,7 / 15.9 |
| M20 | 245 / 0.3798 | 147 / 33.0 | 110 / 24.8 |
| M24 | 353 / 0.5472 | 212 / 47.6 | 159 / 35.7 |
| M30 | 561 / 0.8696 | 337 / 75.7 | 252 / 56.8 |
Standard equivalences
Section titled “Standard equivalences”There is no direct ISO replacement for spring washers, since the ISO 7089 series covers only flat washers. However, DIN 127 functionally overlaps with the following international standards:
| Standard | Description | Equivalence |
|---|---|---|
| DIN 127 B | Spring washer, flat ends (most widely used) | BN 672 (Bossard), functional equivalent to ASME B18.21.1 type B |
| ASME B18.21.1 | Helical spring lock washers (split lock washers) | Interchangeable in inches; for metric, DIN 127 is recommended |
| UNI 1751 | Spring washer (Italy) | Dimensions virtually identical to DIN 127 |
| BS 4464 | Spring lock washers (United Kingdom) | Metric equivalent; currently withdrawn and replaced by DIN 127 |
| JIS B 1251 | Spring lock washers (Japan) | Same dimensions for the covered diameters |
Applications
Section titled “Applications”DIN 127 washers are used in bolted joints subjected to moderate dynamic loads and temperatures up to 200 °C / 392 °F in carbon steel, although the A2 stainless steel version withstands up to 300 °C / 572 °F. They are common in agricultural machinery, steel structures, transportation equipment, and home appliances. They are not recommended for critical joints where precise preload control is required, nor for flanges with O-rings, where flat washers with surface treatment offer better sealing.
Design notes
Section titled “Design notes”- Reusing a DIN 127 washer after disassembly reduces its elastic capacity by at least 30%, therefore systematic replacement is recommended.
- The washer must rest on a flat surface perpendicular to the bolt axis; on parts with cast surfaces, a flat washer DIN 125 should be interposed.
- The cut end is oriented toward the fixed piece and the raised end toward the bolt head or nut.
- For diameters larger than M39, wave spring washers or chemical locking systems are used.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What are the dimensions of a DIN 127 washer for an M10 bolt?
Section titled “What are the dimensions of a DIN 127 washer for an M10 bolt?”The DIN 127 B washer for M10 has an inner diameter of 10.2 mm / 0.402 in, outer diameter of 18.1 mm / 0.713 in, and thickness of 2.5 mm / 0.098 in, with an approximate weight of 1.64 g / 0.058 oz per piece.
What is the recommended tightening torque for an M8 8.8 bolt with a spring washer in dry condition?
Section titled “What is the recommended tightening torque for an M8 8.8 bolt with a spring washer in dry condition?”The recommended dry tightening torque for M8 class 8.8 is 23 Nm / 16.96 ft·lb; if the bolt is lubricated, the torque is reduced to 17 Nm / 12.54 ft·lb to avoid overloading the washer.
What is the maximum force to which an M12 class 8.8 can be tightened with a DIN 127 washer?
Section titled “What is the maximum force to which an M12 class 8.8 can be tightened with a DIN 127 washer?”The maximum allowable clamping force for M12 8.8 is 37.9 kN / 8.53 kip, equivalent to 75% of the bolt proof load, which keeps the washer within the elastic regime.
Which ANSI standard is equivalent to DIN 127?
Section titled “Which ANSI standard is equivalent to DIN 127?”The functional equivalent in inches is ASME B18.21.1 (helical spring lock washers), which defines two types: type A with beveled ends similar to DIN 127 A, and type B with flat ends analogous to DIN 127 B.
What material predominates in DIN 127 washers and what hardness does it achieve?
Section titled “What material predominates in DIN 127 washers and what hardness does it achieve?”The standard material is C67S spring steel hardened and tempered, with a surface hardness of 42 to 50 HRC; the A2 stainless steel versions have a hardness of 25 to 35 HRC / 255 to 335 HV.
What is the service temperature limit of a carbon steel DIN 127 washer?
Section titled “What is the service temperature limit of a carbon steel DIN 127 washer?”The carbon steel version retains its elastic properties up to 200 °C / 392 °F; above this temperature, temper loss and spring relaxation occur, while the A2 stainless steel variants can operate up to 300 °C / 572 °F.