Oil Level Sight Glass (Bullseye Type)

KOK designs and manufactures bullseye oil level sight glasses (guarded type) for oil-containing housings and mechanical assemblies where a fixed visual confirmation of oil presence or level is required at a defined installation height.

These components provide a direct visual reference through a transparent inspection window. The oil level observed corresponds to the installation position on the housing, rather than a measured range.

Functional Role & Application Context

Bullseye oil level sight glasses act as static inspection points within oil-filled components such as gearboxes, reducers, and enclosed mechanical systems.

They are used where:

• Oil presence or nominal level must be visually confirmed
• The reference level is defined by component placement
• Continuous level measurement is not required

The guarded design protects the viewing window from accidental impact or external mechanical contact.

Design & Construction

KOK bullseye sight glasses consist of:

• A metal housing
• A transparent inspection window
• An integrated protective metal guard

Design considerations include:

• Threaded or press-fit mounting interfaces (application dependent)
• Sealing via O-ring or gasket
• Housing wall thickness and material compatibility
• Clear visibility at the defined inspection height

The bullseye configuration provides a compact, robust solution suitable for confined or exposed installation environments.

Materials & Compatibility

Inspection windows are manufactured from materials selected for optical clarity, durability, and compatibility with oils and additives, including:

• Acrylic
• Polyamide
• High-performance copolyesters

Material selection is defined based on operating temperature, oil chemistry, and long-term exposure to minimise clouding, cracking, or discoloration.

Operating Conditions

KOK bullseye oil level sight glasses are designed for:

• Continuous exposure to oil
• Static or low internal pressure conditions
• Mechanical vibration and thermal cycling typical of enclosed machinery

Manufacturing Control & OEM Supply

All bullseye oil level sight glasses are manufactured under controlled production processes to ensure dimensional accuracy at mounting and sealing interfaces, reliable sealing performance, and consistent optical quality across production batches.

KOK supplies bullseye oil level sight glasses to OEM customers, supporting both standard designs and application-specific configurations from development through series production.