Page 21 - february

METALWORKING EQUIPMENT AND TOOLS

preload value for linear Rolling guides are usually equal to about 1/3 of the load if the rolling
elements are balls (steel), and about 1/2 of the load if rollers (cylindrical) are used. If the
guideways must have very high rigidity to resist vibration or alternating loads, then the preload
value can be increased.

Table 1. Coefficient of friction

Series Dynamic friction coefficient μ (1)

Linear guide 0,0040 – 0,0060

Linear roller guide 0,0020 - 0,0040

Slotted ball guide 0,0020 - 0,0040
Cross roller guideway 0,0010 – 0,0030

Precision linear slide 0,0010 – 0,0020

Linear bearing 0,0020 – 0,0030

Short Stroke Rotating Bushing 0,0006 – 0,0012

Flat roller cage 0,0010 – 0,0030

Note (1). These coefficients of friction do not include seal friction.

PRECAUTIONS WHEN SELECTING A PRESET
Even if very high stiffness is to be obtained, excessive preload should be avoided, as it
creates high stresses between the rolling elements and the raceways, which ultimately leads to a
reduction in the resource of the rolling guides. It is important to select the correct preload value
for the operating conditions. If linear rolling guides are to be operated at high preloads, contact
the manufacturer for more information. Linear bearings and short stroke rotary bushings should
never be operated with high preload.

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