: A "short" undercut used when space is tight, though it requires more precision and specialized tools.
(Note: DIN 76 also defines Forms C and D, but these are for internal threads such as blind tapped holes, where the groove diameter is machined larger than the nominal diameter.) Understanding DIN 76 Form A Geometry
To safely integrate these measurements into CAD software (like SolidWorks, AutoCAD, or Fusion) or to program CNC lathes, it is always recommended to reference the official, authoritative technical documents.
During the manufacturing of external threads—whether via chasing, rolling, or milling—the threading tool cannot cut a full, perfect thread profile all the way to a perpendicular shoulder. It naturally leaves a partial, non-functional thread form known as a thread run-out. din 76a pdf
): This defines the length of the transitional threads leading into the relief groove.
Among the globally recognized standards for these geometries, is the premier specification for external thread undercuts for metric ISO threads. What is DIN 76-A?
The DIN 76 series of standards (specifically DIN 76-1 and DIN 76-2) defines the dimensions for thread run-outs and thread undercuts for fasteners : A "short" undercut used when space is
You can find detailed documentation and technical diagrams for this standard on several platforms: Standard Previews
The Ultimate Guide to DIN 76-A: Understanding Thread Undercuts and Specifications
) will have a much wider and deeper undercut than an M12 fine thread ( It naturally leaves a partial, non-functional thread form
Without access to a proper , engineers make three critical errors:
(bolts/screws). It is used when there are no strict space limitations. : A "short" design for external threads
You can find the PDF here: