Hairspring: Diameter 4-12 mm, Active Length 200-400 mm

Q: What is the purpose of a hairspring in a mechanical movement?

The hairspring regulates the oscillation frequency of the balance wheel, serving as the timekeeping element that controls the accuracy of the mechanical movement through precise elastic deformation cycles.

Q: Why are hairsprings made from special alloys?

Special alloys like Nivarox and Elinvar provide minimal thermal expansion, excellent elasticity, and resistance to magnetic fields and corrosion, ensuring stable timekeeping across varying environmental conditions.

Q: How does hairspring geometry affect timekeeping accuracy?

The coil spacing, thickness, and overall geometry determine the spring constant and moment of inertia, directly influencing the oscillation frequency and isochronism (consistent period regardless of amplitude).

Component Specifications

Definition

The hairspring is a critical precision component in mechanical timekeeping devices, consisting of a thin, coiled spring typically made from specialized alloys. It works in conjunction with the balance wheel to create a harmonic oscillator that controls the rate of timekeeping through precise elastic deformation and recovery cycles. The hairspring's geometry, material properties, and thermal characteristics directly determine the accuracy and stability of the timing mechanism.

Working Principle

The hairspring operates on Hooke's law of elasticity, where the spring's restoring force is proportional to its displacement from equilibrium. When the balance wheel rotates, the hairspring coils and uncoils, creating a periodic oscillation with a specific frequency. This oscillation frequency serves as the timebase for the movement, with the hairspring's stiffness and moment of inertia determining the oscillation period through the formula T=2π√(I/k), where I is the moment of inertia and k is the spring constant.

Materials

Typically made from specialized alloys including: Nivarox (iron-nickel-chromium-titanium), Silicon (Si) for MEMS applications, Glucydur (beryllium-copper), or Elinvar (iron-nickel-chromium). Modern high-end applications may use silicon with DRIE (Deep Reactive Ion Etching) manufacturing.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Diameter	4-12 mm
Frequency	2.5-4 Hz (18,000-28,800 vph)
Thickness	0.02-0.05 mm
Active Length	200-400 mm
Number Of Coils	10-14
Spring Constant	0.0001-0.001 N·m/rad
Temperature Coefficient	<1 second/°C/day

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 3159, DIN 8308, NIHS 95-10

Parent Products

This component is used in the following industrial products

Gauge Movement

The internal mechanism of a temperature gauge that converts thermal expansion into pointer movement.

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Engineering Analysis

Risks & Mitigation

Magnetic interference
Thermal expansion effects
Fatigue failure
Shock damage
Corrosion in humid environments
Hairspring sticking or tangling

FMEA Triads

Trigger: Magnetic field exposure
Failure: Altered spring constant leading to timing errors
Mitigation: Use anti-magnetic alloys (Nivarox, silicon) or magnetic shielding

Trigger: Mechanical shock
Failure: Deformation or breakage of delicate spring
Mitigation: Implement shock protection systems (Incabloc, Kif) and proper handling procedures

Trigger: Temperature variations
Failure: Thermal expansion altering spring properties
Mitigation: Use temperature-compensating alloys (Elinvar) with low thermal coefficients

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.005 mm diameter, ±0.001 mm thickness, ±1° coil spacing

Test Method

ISO 3159 chronometer testing, frequency measurement with timing machines, thermal compensation testing, magnetic resistance testing per NIHS 90-10

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

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Manufacturers of Hairspring

Manufacturer profiles associated with Hairspring.

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Frequently Asked Questions

What is the purpose of a hairspring in a mechanical movement?