F8-16M thrust ball bearing 8 × 16 × 5 mm for Z axis and lead screw

The F8-16M is a single-direction thrust ball bearing designed to transfer forces parallel to a shaft between a rotating component and a fixed support. Its nominal 8 × 16 × 5 mm dimensions make it particularly useful in Z-axis drives with an 8 mm lead screw, installed underneath the coupling.

HTA3D uses this bearing in the HPRO-330 and HPRO-400. The coupling rests on the bearing so that the Z assembly's axial load is transferred to the mount and frame, instead of placing the entire weight directly on the motor rotor and its internal bearings.

Dimensions and construction

• Reference: F8-16M.
• Nominal bore diameter: 8 mm.
• Nominal outside diameter: 16 mm.
• Overall height: 5 mm.
• Shaft washer: 8 mm bore and nominal 15.8 mm outside diameter.
• Housing washer: nominal 8.2 mm clearance bore and 16 mm outside diameter.
• Rolling elements: cage with 9 balls.
• Construction: open and separable into three components.
• Contents: 1 complete bearing.

Use underneath a Z-axis coupling

In a correctly designed vertical assembly, one washer is supported by the stationary mount while the other rotates with the coupling or lead screw. The facing raceways and ball cage allow rotation while transferring the vertical force to the frame.

Rat Rig uses the same principle in documented designs including the V-Core 3.0, V-Core 1.3 Pro and V-Core 3.1 IDEX. The V-Core 3.0 guide specifically states that the coupling must rest on the thrust bearing to take the load off the motor shaft. This confirms the purpose of the arrangement, but it does not mean that every Rat Rig revision uses the same part: check the bill of materials for the exact machine.

Installation

1. Check that the housing accepts a 16 mm diameter and 5 mm height, and that the shaft or lead screw is nominally 8 mm.
2. Place the washer with the 8.2 mm bore on the fixed support and the 8 mm washer towards the rotating component.
3. Orient the machined raceway on each washer towards the ball cage.
4. Rest the 5-to-8 mm flexible coupling or 5-to-8 mm rigid coupling on the moving washer only when the Z-axis architecture is designed for this arrangement.
5. Seat the assembly without excessive preload and confirm that one washer can rotate relative to the other.
6. Align the motor, coupling and lead screw before checking the complete Z travel. A thrust bearing does not correct lateral misalignment.

Cleaning and lubrication

This is an open bearing, so keep its raceways free from dust, filament debris and metal particles. If lubrication is required, use a small amount of suitable bearing grease. Excess lubricant can retain contamination and increase drag.

We do not publish a universal load capacity or limiting speed: these values depend on the manufacturer, materials, tolerances and lubrication of each production batch. In a Z axis, selection must also consider the actual moving mass, number of supports and assembly geometry.

It is for you if...

• You want to unload a Z motor shaft by adding an axial support underneath the coupling.
• Your design specifies an F8-16M or an 8 × 16 × 5 mm thrust bearing.
• Your housing supports one washer while allowing the other to rotate freely.

It is not for you if...

• You need to support radial load or guide the lead screw laterally.
• Your shaft, housing or available height does not match 8, 16 and 5 mm.
• You are trying to correct misalignment between the motor, coupling and lead screw.

It can be combined with a TR8×8 trapezoidal lead screw when the mechanical design includes this support. Sharing a nominal 8 mm diameter does not prove compatibility by itself: the housing, coupling, height and travel must also match.