Round/Knuckle Thread \\ Fillet / Chamfer Tab (Tab 2):

Set the radius or chamfer size on corners of the thread profile.

Fillet/Chamfer : Value here is the calculated radius/chamfer for the thread defined in Tab 1.

Chamfer Angle : Angle of chamfer. Click the radio button to switch to chamfer. The value in the Fillet/Chamfer input box will then be used as the size of the chamfer.

For Knuckle threads, the Crest values for both sides must be equal and the Root values must be equal.

Refactoring of Knuckle Threads (DIN405)
Knuckle Threads, (spesifically DIN405 threads) must have a fully rounded crest and root.
The DIN405 spec give a spesific formula for calculating these radiuses using fixed numbers and multiplying these with the pitch.
Using these fixed numbers, combined with supplying two tolerance classes will often result in not everything adding up correctly.

Pressing the "Refactor Rad" button, will try to adjust the crest and root radius a tiny bit and create this inaccuracy as small as possible.
After pressing the "Refactor Rad" button the new values should give a slightly more accurate profile.