The Bulova Caliber 247 is a manual-winding mechanical movement from the mid-20th century, part of Bulova’s broader family of small-sized calibers built for slim wristwatches and elegant dress models. Known for its compact construction and dependable operation, Caliber 247 shares architectural similarities with its siblings (Cal. 245 and 246), while incorporating small design variations for specific case or dial configurations.

Technical Specifications

• Movement Type: Manual-winding

• Jewels: Typically 17

• Frequency: 18,000 vibrations per hour (vph)

• Diameter: Approx. 10.5 ligne (≈23.7 mm)

• Height: ~4.0 mm

• Functions: Hours, minutes, and small seconds (at 6 o’clock in most versions)

• Shock Protection: Commonly Kif or Incabloc

• Mainspring: Barrel with removable cover, designed for easy replacement

This caliber was designed to fit in smaller, often gold-filled or steel cases, particularly those used in Bulova watches marketed between the 1950s and 1960s.

Construction and Features

• Train Layout: Classic Swiss lever escapement with center wheel drive.

• Balance: Flat hairspring with an adjustable regulator arm.

• Winding and Setting: Utilizes a traditional stem, clutch, and setting lever configuration for time-setting and winding.

• Power Reserve: Typically between 36 and 42 hours when fully wound.

The movement features a solid three-quarter plate over the gear train, providing robustness and ease of serviceability.

Servicing and Maintenance

Disassembly

• The movement disassembles in a conventional sequence:

  • Remove dial and hands.

  • Unscrew bridges and lift gear train components.

  • Access keyless works through the dial side.

• The small seconds wheel requires gentle handling during removal and reinstallation.

Lubrication

• Use Moebius 9010 for train pivots and 941 for escapement lubrication.

• Mainspring barrel should be cleaned and re-greased or replaced if set (loss of elasticity).

• Keyless works should be lightly greased at contact points to ensure smooth operation.

Common Issues

• Low amplitude due to old or gummed-up oils.

• Balance staff wear, especially on watches that suffered drops or impacts.

• Stem or clutch wear, resulting in loose or ineffective winding.

Parts Availability

Replacement parts for the 247 remain available through vintage parts dealers and donor watches. Common components still found include:

• Winding stems

• Mainsprings

• Balance wheels and staffs

• Escape wheels and pallet forks

Given its similarity to Calibers 245 and 246, some parts are interchangeable, though caution is needed to verify dimensions.

Summary

The Bulova Caliber 247 is a compact and reliable hand-wound movement that continues to serve well in restored vintage timepieces. Its durability, simple design, and ease of servicing make it a good choice for both beginner and experienced watchmakers looking to work on classic Bulova watches. With careful maintenance, these movements offer decades more of accurate timekeeping and vintage charm.