Open linear ball bearings are supplied with a wet or dry preservative and can be lubricated using either grease or oil. The oil-based preservative is compatible and miscible with lubricants having a mineral oil base, which means that it is not generally necessary to wash out the bearings before fitting.

Bearings with a dry preservative must be greased or oiled immediately after they are removed from the packaging.

Grease lubrication should be used in preference to oil lubrication, since the grease adheres to the inside of the bearing and thus prevents the ingress of contamination. This sealing effect protects the rolling elements against corrosion.

In addition, the design work involved in providing grease lubrication is less than that for providing oil, since design of the sealing arrangement is less demanding.

The greases for linear ball bearings have the following composition:

• lithium or lithium complex soaps
• base oil: mineral oil or poly-alpha-olefin (PAO)
• special anti-wear additives for loads C/P ＜ 8, indicated by “P” in the DIN designation KP2K–30
• consistency to NLGI class 2 in accordance with DIN 51818.

Based on experience, the operating life is achieved when bearings are operated with grease lubrication in normal environmental conditions (C/P ＞ 10), at room temperature and at v ≦ 0,6 · v_max. If it is not possible to achieve these conditions, the bearings must be relubricated.

Sealed linear ball bearings are already adequately greased when delivered and are therefore maintenance-free in many applications.

The initial greasing and relubrication of linear ball bearings without seals and relubrication holes must be carried out via the shaft. It must be ensured that all rolling elements come into contact with grease during recirculation. The bearing must be moved over at least twice its length during relubrication.

During initial greasing, the bearing fitted on the shaft should be fed with lubricant until this begins to emerge from the bearing.

In linear ball bearings KH, KN..-B-PP-AS, KS..-PP-AS and PAB..-PP-AS, relubrication can be carried out via holes or openings in the retaining ring or outer ring.

The relubrication interval is dependent on many operating conditions such as load, temperature, speed, stroke length, lubricant, environmental conditions and the mounting position.

The precise lubrication intervals should be determined by tests conducted under application conditions.

If linear ball bearings are mounted in a housing, special nozzle tubes may be required for relubrication, Figure 1 and Figure 2. Sources for nozzle tubes with suitable needle point heads can be requested from us.

Lubrication nipples for housings with KS are shown in Figure 3, suitable DIN lubrication nipples for housings with KN-B are shown in Figure 4 and Figure 5, for other housings, Figure 6. The dimensions are given in the tables.

In vacuum applications, lubricants with low vapourisation rates are required in order to maintain the vacuum atmosphere.

In the foodstuffs sector and clean rooms, special requirements are also placed on lubricants in relation to emissions and compatibility. For such environmental conditions, please consult us.

Oil lubrication should be used in preference if heat is to be dissipated and contaminants are to be carried out of the bearing by the lubricant.

This advantage should be set against the increased design work required (lubricant feed, sealing).

As a function of the load case, we recommend the following oils:

• At low to moderate loads (C/P ＞ 15):
  • Hydraulic oils HL to DIN 51524 and oils CL to DIN 51517 in the viscosity range ISO-VG 10 to ISO-VG 22.
• At high loads (C/P ＜ 8):
  • Hydraulic oils HLP to DIN 51524 and oils CLP to DIN 51517 in the viscosity range ISO-VG 68 to ISO-VG 100.