DIN 6535 is a German standard that defines the cylindrical shank dimensions and forms for solid carbide cutting tools (such as end mills, drills, and reamers).
There are three common types:
DIN 6535-HA
Plain cylindrical shank
Smooth, without flats; typically used with standard collet chucks.DIN 6535-HB
Cylindrical shank with one flat
Provides anti-rotation; commonly used in Weldon-type holders.DIN 6535-HE
Cylindrical shank with two flats
Offers stronger clamping stability; ideal for heavy-duty machining with high torque.Ø1 mm to Ø25 mm (varies depending on the tool type)
Shank length and tolerance are also specified in the standard.
HA → best for high-precision machining (finishing, drilling), quick tool changes.
HB/HE → best for roughing, heavy cutting, or when higher torque transmission is required.
