Classic Shutter Mechanism Disassembly and Maintenance: Degreasing and Cleaning Standards for Mechanical Leaf Shutters

1. The precise physical structure of the mechanical shutter (Leaf Shutter)

The interlens shutter is installed at the physical aperture plane between the front and rear elements of the lens (such as the Synchro-Compur or Copal shutter in Rolleiflex, Hasselblad V-series C/CF lenses, large-format Xana/Lynhaff lenses):

1. Starburst overlapping blade mechanism:

• 5 to 7 ultra-thin and highly elastic blued spring steel blades overlap each other in an annular shape;
• When the shutter is released, the drive ring drives the blade pin to instantly open to the surroundings at extremely high acceleration. After staying for a specified time, the spring mechanism violently pulls back and closes.

2. Slow-Speed Escapement gear set:

• When shooting at slow speeds of 1 second, 1/2 second, and 1/4 second, a set of micro clock-grade gear reducers and a hairspring flywheel (Pallet & Escape Wheel) perform mechanical delay after the shutter is fully opened.

3. The mechanism of the fatal terminal disease "Sticky Shutter":

• The mechanical failure of most old cameras is not due to gear wear or breakage, but rather to the oxidative polymerization and migration of oil molecules caused by the animal bone oil or mineral grease injected decades ago;
• The thick grease evaporated covered the surface of the shutter blade between the lenses. Since the gap between the leaves is only a few microns, the dried oil forms an extremely strong liquid surface tension viscosity between the leaves!
• Symptoms: After the shutter is pressed, the blades open, and then get stuck in the fully open position and are unable to rebound and close (the 1 second slow shutter often delays for several minutes before being unable to rebound), and the machine is completely paralyzed.

2. It is strictly forbidden to use WD-40 when selecting chemical degreasing solvents.

Many lay users just spray WD-40 anti-rust lubricant when they see the machine is stuck. This is a devastating operation that directly sentences the lens to death:

1. WD-40’s Second Disaster:

• WD-40 contains a large amount of low boiling point volatile solvents and mineral protected heavy oils. It seems smooth for a short time after spraying, but after a few weeks, the solvent evaporates and leaves an extremely stubborn and sticky oil film, which completely sticks the shutter blade and aperture blade into an iron plate, and quickly spreads to contaminate the front and rear lens coatings.

2. Professional and safe degreasing solvent list:

• High-purity industrial isoheptane/cyclohexane (Heptane): extremely strong degreasing power, evaporates very quickly, and leaves no water traces;
• High Quality Lighter Fluid (Zippo / Stellar Lighter Fluid, Light Naphtha Refined Fraction): The most efficient and safe degreaser available in home darkrooms, non-corrosive to blued steel and brass gears;
• Waterless Electronic Grade Isopropyl Alcohol (IPA 99.9%): For secondary rinse.

3. Standard method of step-by-step immersion cleaning and ultrasonic degreasing

1. Completely disassemble all glass lens groups (absolute prerequisite):

• You must use a tic-tac-toe wrench to unscrew the front and rear lenses of the lens and store them properly in the dust-proof box!
• It is absolutely strictly prohibited to soak with lenses! Any solvent that penetrates into the interior of Doublet Cemented Elements will instantly dissolve Canada Balsam or optical UV glue, causing the lens to become permanently debonded, bleached and scrapped.

2. Local drip infiltration cleaning method (mildly sticky):

• Expose the shutter blade and slow door gear set;
• Use a glass syringe to draw 0.5ml of pure lighter oil, and drop a very small amount on the overlapping gap of the shutter blades and the axis of the slow-release escapement wheel;
• Wind and release the shutter 30 times with your fingers! As the solvent dilutes the sludge, the shutter, which was originally pinned and astringent, instantly emits a crisp and cheerful "click-click" mechanical sound;
• Immediately use a pointed dust-free cotton swab to gently absorb the oozing dark yellow turbid oil stain repeatedly until the cotton swab appears absolutely white.

3. Ultrasonic vibration degreasing of the whole machine (severe hardening):

• Immerse the entire mechanical shutter body into a beaker containing isoheptane;
• Place it in an ultrasonic cleaning machine and vibrate at low power for 3 minutes. The micron-level cavitation bubbles will completely peel off decades of aging oil and dirt inside the tooth grooves;
• Take it out and place it on a dust-free workbench, use the low setting of the heat gun (40℃ pure warm air) to gently blow it to dry completely.

4. The ultimate iron law of lubrication: Never add liquid oil to "dry operation"

Many users mistakenly believe that they must "add engine oil" after cleaning. This is completely wrong:

1. Shutter blade must be in 100% absolute dry state (Dry Operation):

• It is strictly prohibited to add any trace amount of liquid lubricant to the surface of the shutter steel!
• The movement inertia of the blades between the mirrors is extremely weak, and they rely solely on the explosive force of the spring to push and pull. Any liquid grease will produce fluid shear resistance when moving at high speed, resulting in a serious delay in exposure time.

2. Micro-Fine Graphite Powder:

• If the gear shaft hole pivot needs lubrication, only ultrafine (above 2000 mesh) high-purity dry graphite powder is allowed;
• Use the tip of a needle to pick up a very small amount of graphite powder the size of dust and point it into the bearing groove to blow away the floating powder to achieve the ultimate dry lubrication.

3. Shutter Tester Calibration:

• Lighting test on photoelectric shutter speed tester: 1/500s, 1/125s, 1/1s. The error must be narrowed within the $\pm 15%$ tolerance specified in the national standard before assembly and delivery.

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