Thread undercuts are easy to add with Creo Elements/Direct Part Library. Define a threaded face first, unless you want to add the thread, chamfer, and undercut to a circular face in one step, like this:
Several standard undercut types are available:
• Type A: DIN 76 type A (normal case) is created on a shaft.
• Type B: DIN 76 type B (short form) is created on a shaft.
• Type C: DIN 76 type C (normal case) is created in a hole.
• Type D: DIN 76 type D (short form) is created in a hole.
By default, undercuts are added as user-defined features. You can change this in the Defaults dialog box. Click (dialog box launcher) in the Features group to open the Defaults dialog box.
To add an undercut to a threaded face,
1. Click Part Library and then, in the Feature group, click the arrow next to Thr. U.-cuts.
2. Click on the undercut type you want. Select a command in the Bolt and Thread Undercut section if you also want to add an outer thread and chamfer to a circular face.
3. Set the undercut dimensions and options. Please note the following:
◦ The thread pitch is taken from the thread face adjacent to the selected edge. To change it, click thread pitch and select from the list of standards.
◦ DIN standards only allow two blend angles: 30 and 60 degrees.
◦ The direction must be along the axis of the cylindrical face. You usually do not need to change this.