TORSION SPRINGS

Custom Torsion Springs · Engineering Review · Drawing Fast-Track

Torsion Spring drawing
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Leg / End Configurations — How Your Spring Attaches

Torsion spring ends can be formed in various ways to suit your application. The leg type affects installation, torque transmission, and available space

Straight Leg

Torsion Spring Straight Leg
  • Tangential exit from body
  • General industrial，consumer goods

Offset Leg

Torsion Spring Offset Leg
  • Bent radially inward/outward
  • Around shafts, flanges,tight spaces

Hinge Leg

Torsion Spring Hinge Leg
  • 90° bend, forms pivot point
  • Clipboards, clothespins,door hinges

Short Hook

  • Small hook, quick connect
  • Toys, appliances, temporary assemblies

Hook End

  • Full hook, secure retention
  • Permanent assemblies,moderate loads

Double Torsion

  • Two coils, left + right wind, connected by arm
  • Balanced torque, zero side load

Spring Index — Manufacturability & Design Guide

Spring index (C = mean diameter / wire diameter) determines how easily your torsion spring can be produced — and how it behaves in use.

C < 4

  • not feasible in most cases
  • Arbor breakage risk during winding
  • Inner surface stress cracks from extreme bending
  • Cannot be run on standard coiling machines

C = 4–5

  • possible but with limitations
  • Requires special tooling and experienced setup
  • Higher cost per part due to slower production
  • Limited tool life increases maintenance frequency

C = 6–12

  • recommended range
  • Stable winding process, consistent torque output
  • Good surface finish, long tool life
  • Best balance of cost, quality, and production speed

C > 12

  • production slowdown
  • Winding speed drops significantly (coils tend to slip)
  • Coils sag, causing inconsistent torque between coils
  • Final dimensions (free angle, mean diameter) hard to control

Dynamic effect: As the spring deflects, coil diameter decreases — effective C changes during operation. Designs with low initial C need extra margin.

After Coiling — What Makes a Torsion Spring Reliable

The way a torsion spring is finished determines whether it performs consistently — or drifts, sags, or fails early.

Stress Relieving

  • Removes residual stress from colding forming
  • Prevents dimensional change and premature failure

Presetting-optional

  • Stabilizes torque and free position
  • Load and free length remain stable from first cycle to millionth

Shot Peening-optional

  • Includes compressive residual stress
  • Blocks crack growth — fatigue life increases 3–5×

These steps are not automatically applied to every spring. They are engineering decisions — selected based on your load profile, cycle requirements, and operating environment. 

Torsion springs

Wire Cross‑Section

  • Round Wire
  • Square / Rectangular

Common Materials

  • Music Wire
  • Oil Tempered Wire — incl. alloy grades
  • Carbon Steel
  • Stainless Steel
  • Inconel / Hastelloy
  • Phosphor Bronze / Beryllium Copper

Finishes

  • Electroplating（Zinc, nickel and ect)
  • Electroless Plating(NIckel)
  • Black Oxide
  • Phosphating
  • Passivation (for stainless steel)
  • Chromating
  • Powder Coating
  • Vacuum Coating (PVD, IP plating)
  • Polishing / Buffing
  • Oil Coating
  • Zinc-Nickel Alloy Plating
  • Geomet
  • Dacromet
  • Anodizing (for non-ferrous)
  • Teflon (PTFE)
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