Bulova 6BL Teardown: Vintage Watch Disassembly & Service Manual

The Bulova 6BL is a classic 17-jewel, manual-wind ladies' mechanical movement produced during the mid-20th century. Measuring just 6¾ by 8 lignes (approx. 15.3mm x 17.8mm), this compact tonneau-shaped calibre represents the golden age of American watch engineering. For aspiring horologists and restoration hobbyists, disassembling a vintage 6BL teaches fine motor control and gear train fundamentals.

Preparation & Safety: Working on Miniature Calibres

Because components in a 6BL are less than half the size of standard men's pocket watch parts, work under at least 5x to 10x magnification (such as a Bergeon loupe or stereo microscope). Keep all screws segregated in a multi-compartment Petri tray to ensure each screw returns to its exact threaded hole.

Step 1: De-Powering the Mainspring (Safety First)

Never disassemble a mechanical movement while the mainspring retains tension. Hold the crown firmly between thumb and forefinger, gently disengage the click from the ratchet wheel using a fine pegwood or needle, and allow the crown to unwind slowly in your fingers until all reserve power is completely dissipated.

Step 2: Removing the Balance Assembly & Pallet Fork

Unscrew the balance cock screw and lift the complete balance wheel and hairspring assembly straight up. Store the balance immediately under a protective glass dust cover. Next, remove the pallet bridge and extract the pallet fork with non-magnetic tweezers, taking extreme care not to chip the synthetic ruby pallet jewels.

Step 3: The Going Train & Mainspring Barrel

Remove the ratchet wheel screw (note: some vintage calibres feature reverse left-hand threads) and crown wheel. Unscrew the barrel bridge to expose the mainspring barrel. Next, remove the train wheel bridge to release the escape wheel, fourth wheel (second hand arbor), third wheel, and center wheel.

Step 4: Cleaning, Inspection & Reassembly

Clean all metallic gears, bridges, and pivots in an ultrasonic watch cleaning solution followed by two rinsing stages of pure heptane or watchmaker's rinse. Inspect pivot tips under 10x magnification for wear or bends. During reassembly, lubricate cap jewels with Moebius 9010 synthetic oil and the mainspring with Moebius 8200 grease. Regulate the beat and rate on a digital timegrapher to within +/- 15 seconds per day.