Seiko 6117A Technical Guide

Overview

The Seiko 6117A is a vintage automatic mechanical movement introduced in the mid-1960s. It is renowned for its GMT functionality, allowing the wearer to track multiple time zones simultaneously. This caliber powered several of Seiko’s iconic GMT watches, combining practical features with reliable automatic winding and robust construction.

Specifications

• Caliber: 6117A

• Movement Type: Automatic mechanical with manual winding

• Jewels: 21 synthetic rubies

• Frequency: 21,600 vibrations per hour (3 Hz)

• Power Reserve: Approximately 44 hours

• Functions: Hours, minutes, central seconds, GMT hand, date complication

• Diameter: Approximately 28 mm

• Thickness: Approximately 5.7 mm

Movement Architecture and Components

Mainspring and Barrel

Energy is stored in the mainspring, which can be wound manually or automatically via the rotor, providing about 44 hours of power reserve.

Automatic Winding System

Features Seiko’s bidirectional “Magic Lever” winding mechanism, efficiently winding the mainspring in both rotor directions.

Gear Train

Transfers energy from the barrel to the escapement and hands, including the independent GMT hand.

Escapement

Utilizes a Swiss lever escapement to regulate the release of energy to the balance wheel.

Balance Wheel and Hairspring

Oscillates at 21,600 vibrations per hour, ensuring precise timekeeping.

GMT Module

Includes an independently adjustable 24-hour GMT hand to track a second time zone.

Calendar Module

Date display with quickset adjustment accessible via the crown.

Operation

The rotor winds the mainspring automatically with wrist movement, storing energy that powers the movement. The escapement regulates energy release to the balance wheel, which oscillates to maintain accurate timekeeping. The GMT hand operates independently, allowing the wearer to monitor a second time zone. The date advances daily and can be set quickly through the crown.

Servicing and Maintenance

• Lubrication: Proper application of oils and greases at the mainspring barrel, gear pivots, escapement jewels, rotor bearings, and GMT module components is essential.

• Common Issues: Wear of rotor bearings, mainspring fatigue, and GMT mechanism wear can affect performance.

• Maintenance Schedule: Recommended servicing every 3 to 5 years to clean, lubricate, and regulate the movement.

Summary

The Seiko 6117A is a highly functional and reliable automatic GMT movement, celebrated for its ability to track multiple time zones with precision. Its robust design and practical complications make it a favorite among vintage Seiko collectors and travelers. With regular maintenance, the 6117A continues to offer accurate and dependable performance.