Spring Steel Grades Explained: SM/DM, SH/DH and SS304

When you order a spring from a manufacturer in India, you will often see references to wire grades such as SM/DM, SH/DH or SS304.

Most buyers know they need a spring steel spring — but are not sure which grade to specify, or what the difference is.

This guide explains the four most common wire grades used in spring manufacturing in India, and when to use each one.

What Do SM, DM, SH and DH Stand For?

The letters describe two things: the carbon content of the wire, and the number of times it was drawn (pulled through a die to reduce its diameter and increase its tensile strength).

•  SM — Single draw, Medium carbon

•  DM — Double draw, Medium carbon

•  SH — Single draw, Hard (high carbon)

•  DH — Double draw, Hard (high carbon)

A higher number of drawing passes produces a wire with tighter dimensional tolerances and more consistent mechanical properties. Double drawn wire (DM and DH) is more consistent than single drawn wire across a production batch.

Higher carbon content (SH and DH) produces a harder, stronger wire with higher tensile strength and better fatigue resistance.

Grade SM/DM — Medium Carbon Spring Steel

SM/DM — General purpose industrial use

SM/DM is a medium carbon spring steel wire. It is the standard grade for general industrial applications where load requirements are moderate and the operating environment is not corrosive.

When to use SM/DM

•  General purpose industrial springs — hardware, appliances, consumer products

•  Moderate load applications where high fatigue life is not critical

•  Indoor environments without moisture or chemical exposure

•  Cost-sensitive projects where SH/DH performance is not required

When not to use SM/DM

•  Outdoor agricultural equipment — exposed to soil, moisture and fertiliser

•  High cycle applications — will fatigue faster than SH/DH

•  Heavy load bearing — insufficient tensile strength for demanding applications

Grade SH/DH — High Carbon Spring Steel

SH/DH — Heavy duty, agricultural and high cycle applications

SH/DH is a high carbon spring steel wire. It has higher tensile strength and better fatigue life than SM/DM. It is the recommended grade for demanding applications.

When to use SH/DH

•  Agricultural machinery — cultivators, drawbar connections, harrow tines

•  High cycle applications — springs that compress or extend thousands of times in service

•  Heavy load bearing — where a higher spring rate or load capacity is required

•  Outdoor equipment with zinc plating as corrosion protection

•  Trampoline springs, drawbar springs, octopus springs — all manufactured in SH/DH as standard at Super Springs

If you are unsure whether your application needs SM/DM or SH/DH, choose SH/DH. The performance difference is meaningful and the cost difference is small.

Stainless Steel SS304

SS304 — Corrosion resistant environments, outdoor exposure, food contact

SS304 is an austenitic stainless steel grade. It is corrosion resistant, non-magnetic and food-safe. It is used where the spring will be exposed to conditions that would cause spring steel to corrode.

When to use SS304

•  Outdoor exposure without protective coating — bird spikes, garden equipment, marine hardware

•  Humid environments — Middle East, Southeast Asia, coastal locations

•  Food processing equipment — food-safe and easy to clean

•  Chemical exposure — where spring steel would corrode

•  Medical or pharmaceutical equipment

•  Visible components where appearance matters — stainless has a clean, professional finish

What to know about SS304 vs spring steel

SS304 has a lower shear modulus than spring steel — approximately 73,000 MPa vs 81,500 MPa for spring steel. This means that for the same wire diameter, outer diameter and number of coils, a stainless steel spring will be slightly softer than an equivalent spring steel spring.

If you are converting an existing spring steel design to SS304, the spring rate will change slightly. Mention this to your manufacturer so the dimensions can be adjusted if needed.

SS316 — For More Demanding Conditions

SS316 is a higher grade stainless steel with molybdenum added. It has better resistance to chlorides and aggressive chemicals than SS304.

Use SS316 for marine applications, salt water exposure, chemical processing or medical implants. It is available on request at Super Springs.

Quick Decision Guide

Use this to select the right grade for your application:

•  Standard indoor industrial use, moderate load → SM/DM

•  Agricultural, outdoor, high cycle or heavy load → SH/DH

•  Corrosive environment, food contact, outdoor without coating → SS304

•  Marine, aggressive chemical or medical → SS316

If you are still unsure, share your application details with us — the operating environment, the load requirement and whether the spring will be exposed to moisture or chemicals. We will recommend the correct grade before manufacturing.

Wire Grades Available at Super Springs

We manufacture springs and supply wire rolls in all four grades: SM/DM, SH/DH, SS304 and SS316. Wire rolls are available in grades SM/DM, SH/DH and SS304 in wire diameters from 0.25mm to 2.0mm, supplied in 0.25kg to 2.0kg packs.

About Super Springs

Super Springs has been manufacturing springs and wire components from our factory in Gurgaon, India since 1984. We are an ISO 9001:2015 certified manufacturer supplying OEMs, brands and distributors across 14 countries.

We manufacture in SM/DM, SH/DH, SS304 and SS316 across our full spring range. Custom specifications, low MOQ and export packaging are all available.

View our wire rolls range →  superspringsglobal.com/category/wire-rolls

Request a custom spring quote →  superspringsglobal.com/contact-us