DIN 137-A
Curved Spring Washers
Form A · Manufacturer Mumbai
What Is a DIN 137-A Curved Spring Washers
Not every joint needs a strong locking device or a precisely engineered preload — sometimes all that’s required is a small amount of axial compliance, so a slight variation in torque, plate thickness, or thermal expansion doesn’t leave a joint completely rigid or completely loose. DIN 137 Form A is the most basic way to add that give: a flat washer stamped with a single, gentle dish-shaped curve rather than multiple waves.
That single curve compresses under load and returns a light, distributed spring pressure — considerably less deflection range and a stiffer, more direct force curve than the multi-wave Form B washer, but also simpler and less costly to produce. Form A is specified wherever the axial compensation needed is genuinely modest: taking up a small manufacturing tolerance stack-up, adding light spring tension in an instrument assembly, or simply providing a bit of forgiveness in a joint that doesn’t need serious locking or heavy preload.
Akbar Fasteners Pvt. Ltd. manufactures DIN 137-A curved washers in-house at our Mumbai facility, under ISO 9001:2015, with full mill test documentation, and exports this range to over 50 countries.
Where DIN 137-A Washers Genuinely Earn Their Place
Simple, Low-Cost Compliance
A single stamped curve is the most cost-effective way to add light axial give to a joint without a complex multi-wave form.
Predictable, Modest Deflection
A stiffer, more direct force curve than Form B, suited to applications where only a small compensation range is genuinely needed.
Full Dimension Reference
A published size and thickness chart lets you select the correct washer for your bore, thread, and clearance requirement.
Wide Material & Finish Choice
Spring steel and stainless steel available across the full size range, in bulk quantities for OEM and general assembly needs.
DIN 137-A Curved Washer Dimension Chart
Standard nominal dimensions by thread size — inner diameter (d1), outer diameter (d2), and free-state thickness are the figures to check first against your bore and clearance requirement. Form A’s single-curve profile gives a stiffer, more direct spring response than the multi-wave Form B washer of the same nominal size.
| Thread Size (d) | Inner Dia. (d1) | Outer Dia. (d2) | Free Thickness |
|---|---|---|---|
| M3 | 3.2 mm | 7.0 mm | 0.3 mm |
| M4 | 4.3 mm | 8.7 mm | 0.4 mm |
| M5 | 5.3 mm | 10.2 mm | 0.4 mm |
| M6 | 6.4 mm | 12.2 mm | 0.5 mm |
| M8 | 8.4 mm | 15.8 mm | 0.6 mm |
| M10 | 10.5 mm | 19.0 mm | 0.6 mm |
| M12 | 13.0 mm | 23.0 mm | 0.7 mm |
| M16 | 17.0 mm | 29.0 mm | 0.8 mm |
| M20 | 21.0 mm | 36.0 mm | 1.0 mm |
| M24 | 25.0 mm | 42.0 mm | 1.2 mm |
Figures shown are representative reference values for quick planning purposes; actual deflection characteristics can vary by manufacturer and material temper. Please confirm exact dimensions against the current DIN 137 standard document or your engineering drawing, and request our certified dimensional data sheet, before finalizing a purchase order.
Spring Washer Product Range
Curved Washers (Form A)
Single-curve axial spring washers in spring steel and stainless, M3 to M48 thread reference.
DIN 137-BWave Washers (Form B)
Multi-wave washers for a softer, more linear spring rate and greater deflection range.
DIN 128Spring Lock Washers
Split-ring spring washers providing friction-based resistance to nut loosening.
DIN 2093Belleville Disc Springs
Cone-shaped disc springs for higher load, stacked-configuration spring applications.
DIN 137-A Technical Overview
Available Materials
- Spring Steel Standard Offering
- Stainless Steel A2 / A4 on Request
- Phosphor Bronze Non-Magnetic Applications
- Surface Finish Zinc Plated / Bright
- Custom Material To Specification
Design Details
- Form A (Single Curve)
- Function Light Axial Compensation
- Deflection Range Lower Than Form B
- Hardness Standard Spring Temper
- Testing MTC / NABL on Request
Available Dimensions
- Thread Reference M3 – M48
- Custom Bore Sizes To Drawing on Request
- Profile Single Continuous Curve
- Standard Reference DIN 137-A
- Packaging Loose / Boxed / Bulk
Application Areas
Wherever a joint needs just a small amount of controlled axial give.
General Fastening Assemblies
standard bolted joints
Electrical Panel Assembly
for terminal connections
Instrumentation Assembly
for sensitive assemblies
Small Electric Motors
compensation
Consumer Appliance Assembly
fastening compliance
Electronics & Connectors
pressure in housings
Furniture & Cabinet Hardware
in adjustable fittings
General Light Machinery
modest axial compliance
Standard Export Documentation
Prepared as standard practice for every curved washer shipment.
Mill Test Certificate (MTC)
Material composition and hardness verification for every production batch.
Certificate of Conformance
Confirms the shipment matches the purchase order specification, size, and grade in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Dimensional Data Sheet
Certified inner/outer diameter and thickness data against DIN 137-A available on request before order confirmation.
Bill of Lading
Ocean or air freight shipping document confirming carrier, mode, and consignee details.
Internationally Recognised Standards Coverage
Related Fastener Grades & Standards
DIN 137-B Wave Washers
A softer, more linear spring rate for bearing preload and larger clearance take-up.
View DIN 137-B →DIN 93 Tab Washers
Bendable locking washers offering a physical, verifiable safety locking philosophy.
View DIN 93 →DIN 99 Clamping Levers
Hand-adjustable clamping levers for repeated fixturing and adjustment applications.
View DIN 99 →Top Nickel Fasteners Manufacturer
See our full in-house nickel alloy manufacturing and documentation capability.
View Manufacturer Page →Send Us Your
Bore Size & Application Detail
Tell us your bore size, whether you need Form A or Form B, and material preference — we’ll confirm the correct specification and issue a certified dimensional data sheet with your quote. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in