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Technical datasheet DIN 127B — Split spring washer, square section

Reference only — for design, verification or contractual purposes refer to the current issue of the original standard. MF Fastener Industries LLC · sales@mfindllc.com · +971 6 767 2469 · mfindllc.com

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Dimensional datasheet

DIN 127B spring washer

Split spring lock washer, square section, ground flat. The traditional anti-loosening washer for general assembly. Read the notes before specifying it for a high-tensile joint.

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d₁ inside diameterd₂ outside diameters section thickness

Dimensions

millimetres

Nominal dimensions in millimetres. Form B has a square section with flat ends; Form A is the older rounded-end form and is largely superseded.

For bolt	d₁ — inside	d₂ — outside	s — section	Free height approx
M6	6.1	11.8	1.6	3.2
M8	8.1	14.8	2.0	4.0
M10	10.2	18.1	2.2	4.4
M12	12.2	21.1	2.5	5.0
M16	16.2	27.4	3.5	7.0
M20	20.2	33.6	4.0	8.0
M24	24.5	40.0	5.0	10.0
M30	30.5	49.0	6.0	12.0

A spring washer does little under a high-tensile bolt

Under a class 8.8 or higher bolt the clamp load flattens the washer completely. Once flat it is a plain washer, and it contributes almost nothing to locking.

Spring washers work where the clamp load is modest. For a properly tensioned high-tensile joint the preload itself is what stops loosening — and where vibration is real, use a nyloc, a serrated flange nut or a wedge-lock washer.

Not for structural bolting

Spring washers have no place in an A325 or A490 connection. The RCSC specification does not permit them, and F436 hardened washers serve a different purpose entirely.

Do not substitute one for the other because they look similar.

Forms and alternatives

selection

Option	Standard	How it works	Best for
Split spring, square	DIN 127B	Spring force and edge bite	General assembly
Split spring, rounded	DIN 127A	As above, older form	Superseded
Serrated external tooth	DIN 6798A	Teeth bite both faces	Soft materials, earthing
Serrated flange nut	DIN 6923	Serrations under flange	Vibration, reusable
Nylon insert nut	DIN 985	Insert grips thread	Vibration, ≤ 120 °C
Wedge-lock washer pair	Proprietary	Cam faces resist rotation	Severe vibration

Where a joint has loosened before, changing the washer is rarely the answer. Check the preload first — most loosening is under-tightening.

Materials

—

Material	Finish	Note
Spring steel	Plain, zinc plated	The standard supply
Stainless A2	Self-colour	Lower spring rate than spring steel
Stainless A4	Self-colour	Marine and chloride service

Stainless spring washers are noticeably softer than spring steel and flatten at lower load.

At a glance

Standard	DIN 127B
Form	Split, square section, flat ends
Material	Spring steel · stainless A2 · A4
Older form	DIN 127A, rounded ends
Not permitted in	A325 / A490 structural connections
Better for vibration	DIN 985 nyloc · DIN 6923 flange nut
Plain washer	DIN 125A · ISO 7089
Hardened washer	ASTM F436 · DIN 6916

Supply

Imported and held in stock, sourced from established mills and supplied from our warehouse in Umm Al Quwain.

Anchor bolts, studs and plate washers are manufactured at our own plant. This item is not.

Materials and finish

Spring steel	Plain or zinc plated
Stainless	A2, A4
Hot-dip galvanized	Not usual — coating thickness affects the spring
Certification	Material certificate on request

Testing

Dimensional and thread inspection is carried out in our own plant on calibrated instruments. Tensile, hardness and chemical testing is carried out by independent UAE-accredited laboratories.

Reference only

This datasheet is published for reference. Dimensions and property values are reproduced in good faith from published standards, but for design, verification or contractual purposes always refer to the current issue of the original standard.

If a figure here conflicts with the standard, the standard governs.

Need a quotation?

Send the bolt size, material, finish and quantity. If the joint has loosened in service before, tell us — a different locking method may suit better.