The affix ḍāc comes after the words 1. sapattra and 2. niṣpatra followed by the verb kṛ 'to make' when the sense is that of causing intense pain.,
The word कृ is understood here also. The word ati-vyathana means violent pain. Thus सपत्रा करोति मृगं व्याधः = सपत्रं शरमस्य शरीरे प्रवेशयति \the hunter pierces the stag with the arrow so violently that the feathered part of the arrow also enters the body\. So also निष्पत्रा करोति = शरीराच् छरमपरपार्श्वे निष्क्रामयति \he pierces so voilently that the arrow entering one side comes out of the other with its feathers\. Why do we say when meaning \to cause violent pain\? Observe सपत्रं वृक्षं करोति जलसेचकः, निष्पत्रं वृक्षतलं करोति भूमिशोधकः ॥,