688ZZ shielded ball bearing – 8 × 16 × 5 mm

The 688ZZ is a compact-section deep-groove radial ball bearing with an 8 mm inner diameter, 16 mm outer diameter and 5 mm width. It has metal shields on both sides to help retain lubricant and limit contamination.

It can be used in 3D printers, CNC machines, extruders, rollers, guides, wheels and small rotating mechanisms requiring a compact bearing for an 8 mm shaft.

Nominal 688ZZ bearing dimensions

• Inner diameter: 8 mm.
• Outer diameter: 16 mm.
• Width: 5 mm.
• Type: deep-groove radial ball bearing.
• Protection: ZZ metal shields on both sides.
• Dimensional reference: 688ZZ or 688-2Z.

The 8 × 16 × 5 mm dimensions correspond to the standardised 688 reference. Because the specific manufacturer is not identified, tolerance, internal clearance, lubrication, precision, load capacity and maximum speed may vary. If any of these characteristics is critical, verify it on the supplied unit or select a bearing from an identified manufacturer.

A compact bearing for an 8 mm shaft

The 688ZZ shares an 8 mm inner diameter with several other bearings but uses a particularly compact 16 mm outer body. For example, the 608ZZ also uses an 8 mm shaft but measures 22 mm in outer diameter and 7 mm in width.

These bearings are therefore not interchangeable even though they use the same shaft diameter. Always check all three main dimensions and the housing geometry.

Compatibility and installation

The housing must be designed for a bearing with a 16 mm outer diameter and a width of 5 mm. The inner shaft, sleeve or screw must provide the appropriate diameter and fit for the 8 mm inner ring.

• Clean the shaft and housing before installation.
• Remove burrs that could misalign or damage the bearing.
• Apply insertion force only to the ring being fitted.
• Do not install the bearing by transmitting pressure or impacts through the balls.
• Do not deform the side metal shields.
• Check that the assembly rotates freely after installation.

The ZZ shields provide basic protection against moderate contamination but are not watertight seals. Additional protection may be necessary in environments containing water, fine dust, swarf or abrasive particles.

Flanged version

When the housing requires an integrated lateral shoulder, consider the F688ZZ bearing with an 18 mm flange. It shares the same 8 × 16 × 5 mm shaft and body dimensions but adds a flange on one side.

The flanged version and conventional 688ZZ should not be considered directly interchangeable. The housing must provide sufficient space and suitable geometry for the flange.

When a larger-section bearing for an 8 mm shaft is required, consider the 608ZZ bearing measuring 8 × 22 × 7 mm.

Package contents: 1 688ZZ bearing.