Plain Bearings Typically Handle Only Lower Speeds

Bearings vary greatly over the size and directions of forces that they can support.Forces

can be predominately radial, axial (thrust China Bearing distributor ) or Bending moments perpendicular to the main axis.Different bearing types have different operating speed limits. Speed is typically specified as maximum relative surface speeds, often specified ft/s or m/s. Rotational bearings typically describe performance in terms of the product DN where D is the diameter (often in mm) of the bearing and N is the rotation rate in revolutions per minute.

Generally there is considerable speed range overlap between bearing types. Plain bearings typically handle only lower speeds, rolling element bearings are faster, followed by fluid bearings and finally magnetic SKF bearings which are limited ultimately by centripetal force overcoming material strength.Some applications apply bearing loads from varying directions and accept only limited play or "slop" as the applied load changes. One source of motion is gaps or "play" in the bearing. For example, a 10 mm shaft in a 12 mm hole has 2 mm play.

Allowable play varies greatly depending on the use. As example, a wheelbarrow wheel supports radial and axial loads. Axial loads may be hundreds of newtons force left or right, and it is typically acceptable for the wheel to wobble by as much as 10 mm under the varying load. In contrast, a lathe may position a cutting tool to 0.02 mm using a ball lead screw held by rotating bearings. The SKF bearings distributor support axial loads of thousands of newtons in either direction, and must hold the ball lead screw to 0.002 mm across that range of loads.A second source of motion is elasticity in the bearing itself. For example, the balls in a ball bearing are like stiff rubber, and under load deform from round to a slightly flattened shape. The race is also elastic and develops a slight dent where the ball presses on it.

The stiffness of a bearing is how the distance between the parts which are separated by the bearing varies with applied load. With rolling element bearings this is due to the strain of the ball and race. With fluid china SKF bearings distributor it is due to how the pressure of the fluid varies with the gap (when correctly loaded fluid bearings are typically stiffer than rolling element bearings).

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