Slewing rings      Slewing rings

Slewing rings (base bearings) are used for various applications in many industrial sectors when the rotation of a structural part, with respect to another,is required according to a unique axis, ensuring the bond between the parts. This sector includes the Slewing rings with two rows of balls,  with crossed rollers, but also the with one and two turns of balls, non-toothed and toothed, slewing rings with one, two, three turns of rollers, with internal, external and or without teeth, etc. Distitec produces base bearings in various executions that meet almost all market demands. The sectors we currently supply goes from mining to offshore technology, from the steel industry to the more traditional sectors of industrial handling and lifting of materials and the mechanical industry in general. These products are manufactured according to the general rules relating to rolling bearings, using materials and treatments suitable for good operation which at the same time guarantee the required duration. The photos show some examples of use of these products.

Since Distitec works on specific customer request and offers customized products, it is able to satisfy even small requests in terms of quantity (Distitec produces and delivers in some cases also a single piece).

TECHNICAL FEATURES OF SLEWING RINGS

Slewing rings

The slewing rings produced by Distitec have the following technical characteristics:

Outer and inner rings made mainly in C45 carbon steel (UNI 7845) or 42CrMo4 alloy steel (UNI 7846) both in the initial tempered condition. The use of one material rather than another is linked to specific mechanical requirements, including toughness and hardness, but also to technological factors. 42CrMo4 offers the possibility a greater depth of the hardened layer of the raceways and therefore higher load capacities. C45 (or equivalent) is the material with which most of the standard bearings with small to medium diameters are built, 42CrMo4 is used for medium to large diameters and for many special constructions. The induction hardening to which the sliding races are subjected is necessary to increase the load capacity of the bearing and to preserve the raceways from plasticization phenomena due to contact pressures with the rolling elements. The hardness of the sliding tracks of the rolling elements after this treatment can reach 62 HRc. The depth of hardening varies according to the dimensions and therefore to the loads to be supported.

Rolling elements: The balls, built according to DIN 5401, are used for bearings with four contact points, while cylindrical rollers, built according to DIN 5402, for crossed roller bearings and both are produced in 100Cr6 (UNI 3097) hardened steel. ). The hardness of these elements reaches 64 HRc.
Spacers made of materials such as NYLON or P.T.F.E (TEFLON) with high mechanical characteristics. They are used to keep elements separate and avoid contact. The spacers may not be provided in those applications where the admissible loads of the fifth wheel must be of high bearing capacity.
Seals or gaskets made of NBR nitrile elastomer. This gasket closes the vacuum that is created between one ring and the other, preventing the entry of dirt and impurities, dust and moisture. Proper lubrication increases the effectiveness of the seals.
Grease: The slewing rings that Distitec produces are supplied with an initial lubrication of the ball or roller sliding track with specific greases listed in the use and maintenance manual that we supply together with the product and on which there are indications for a correct periodic relubrication.

 

Grease nipples: Distitec slewing rings are supplied with special grease nipples positioned in the special seats recessed in the diameter where there is no toothing or where it is requested by the customer in special executions.
Cylindrical toothing with straight teeth (see photo) performed respecting all the technical features of this type of toothing. The drawing issued by Distitec indicates all parameters relating to the toothing for a correct execution of the pinion that will mesh with it. The standard surface hardness of the tempered material used reaches a maximum of 30 HRc (42CrMo4) and this hardness value may not always be acceptable to preserve the life of the toothing in some applications. A high rotation torque that produces a high frictional stress on the tooth, high rotation speeds, unfavorable environmental conditions with the presence of dust or abrasive elements, or the need to bring the life cycle of the slewing ring to its maximum, means that the induction hardening treatment is also carried out on the teeth. The treatment can be carried out only on the side or on the side and bottom of the tooth, depending on the loads and the type of application. The maximum surface hardness that can be obtained is 60 HRc.

For more detailed information on tolerances, normal or reduced clearances, surface treatments etc. please refer to the specific slewing rings  catalogue or contact our technical department.

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