The Bulova Caliber 70T is a vintage mechanical movement known for its straightforward design and reliability, particularly popular during the mid-20th century. It was part of Bulova's family of manual-wind calibers designed for dress watches and smaller men's timepieces.

Key Specifications

• Type: Manual-winding mechanical movement

• Jewels: Typically 17 jewels (though variants exist)

• Functions: Hours, minutes, small seconds (usually at 6 o'clock)

• Beat rate: Around 18,000 A/h (2.5 Hz)

• Diameter: Approximately 10.5 ligne (≈ 23.7 mm)

• Height: Roughly 3.9 mm

• Shock protection: Some versions feature Kif or Incabloc systems depending on the market and model year

Design Features

The 70T was engineered with simplicity in mind, using a bridge-style gear train layout that allowed easier servicing. The small seconds complication is driven by a fourth wheel and is commonly found in models with a sub-dial at 6 o'clock.

Other distinguishing characteristics include:

• A large balance wheel providing stable amplitude

• A flat hairspring, often paired with a regulator arm

• A conventional Swiss lever escapement

• Breguet-style gear teeth for efficient power transfer

Servicing and Maintenance

This movement is considered watchmaker-friendly. Disassembly follows standard procedures, with accessible components and generous tolerances. Key servicing notes include:

• Lubrication: Standard oils can be used (Moebius 9010 for train jewels, 941 for escapement).

• Barrel and mainspring: Should be inspected for sticking or wear. Original springs can be replaced with generic equivalents if the exact part is unavailable.

• Hairspring adjustment: Requires care; avoid manipulating the balance wheel without proper tools, as the balance staff pivots are delicate.

Parts Availability

Although the 70T is no longer in production, parts are still available from vintage stock suppliers. Common replacement items include:

• Mainsprings

• Balance staffs

• Crown stems and winding gears

• Train wheels and escape wheels

Common Watches Using 70T

This caliber was used in several Bulova-branded wristwatches from the 1950s and 1960s. These watches are often found in slim, gold-filled or stainless steel cases with domed acrylic crystals and minimalist dials.

Conclusion

The Bulova 70T is a classic example of mid-century watchmaking. Its durable design and simplicity make it a favorite among collectors and repairers. With proper servicing and occasional parts sourcing, these movements can continue running smoothly for decades.