Grinding and turning of top jaws in the chuck
Design and mode of operation
| In order to achieve high concentricity on the chuck, subsequently supplied hard top jaws and one-piece hard stepped jaws should be ground and marked for the work piece machining operation for which they are intended. |  |
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 Fig. 1 In a delivery condition, they suffice for chucking unmachined parts, where the serrations of the gripping surface are useful, but centering accuracy is not required. For exact chucking of already machined surfaces, subsequently delivered top jaws cannot be used without further measures being taken.  The tolerance-related dimension variations of all components involved in the drive of the individual jaws result in varying radial positions of the three jaws as a result of their summation. These differences are greater than the permissible radial eccentricities according to DIN 6386 and can be eliminated by grinding in the chuck in which the jaws are used.  Information on turning as PDF-file |
 Fig. 2 By marking the jaws 1, 2 and 3, it must additionally be ensured that the same jaw is always used in the same guide and with the same base jaw. Jaw grinding must take place in the operational chuck. For grinding stepped jaws (FStB) or hard top jaws (FHB) for external chukking, a mandrel must be clamped as close as possible next to the surface to be ground (Fig. 1). Grinding takes place under clamping pressure. When grinding gripping surfaces for internal chucking, an appropriately dimensioned ring must be slipped over the steps of the jaws and clamped with the same force as used for the actual work (Fig. 2). This applies similarly to turning soft top jaws or monoblock jaws (FMB) or hard turning hardened top jaws in order to obtain a specific clamping diameter. |
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The FORKARDT range of chuck jaws includes a large selection of special jaws and clamping inserts, e.g. for indexing applications. Contact us for more information. |
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Safety information
