Undercut (manufacturing)

A relief groove according to DIN 509 a " removal of a rotationally symmetrical inner edge having a predetermined shape and predetermined dimensions that will provide both the tools used in the production as well as the adjacent part in assembling the required space. "

Here, between undercuts for shafts ( external undercut ) and hubs ( internal undercut ) is distinguished.

Thread undercuts inlets and discharges are set to the standard DIN 76.

Function

The undercut serves to provide open spaces, which are used as run-off areas in the production of tools such as lathe tools and especially grinding wheels. As a functional element of the undercut is required for assemblies / assemblies to ensure the flush plugging of counterparts, if not sufficiently large chamfers or fillets can be attached to these counterparts.

The radius used also reduces stress peaks which arise from paragraphs in the rotational contour and the notch effect.

Standard designation

Are standardized undercuts in DIN 509 As a rule, does not record undercuts in detail, but marks them via a solid line and the standard designation. In the front view of waves Undercuts are not displayed. Unless otherwise stated, undercuts have a roughness of 3.2 microns, which corresponds to a Rauzahl Rz of 25.

Example:

  • DIN 509 - F 0.6 x 0.3 DIN 509 - Standard for Undercuts
  • F - Code letter for the form of undercut
  • 0.6 - radius of the groove
  • 0.3 - depth of the groove

Undercut forms and their application

The two most commonly used forms of undercut E and F, but alternatively find G and H use. The forms A, B, C and D are not used.

  • E - radial groove, when only the outer surface is needed for further processing, such as for external or internal cylindrical grinding
  • F - combined axial and radial penetration for cases in which coat and plane surfaces to be ground, eg with bearing shoulders for rolling bearings
  • G - combined axial and radial groove, which is smaller than the form F and causes a higher stress concentration, but is more space-saving
  • H - combined axial and radial groove having a large radius for reducing the notch effect
  • Machine element
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