As when. Figure of speech Synecdoche (of Species), App-6, one example put for every kind.
head. Hebrew. Iron.
helve. handle. Hebrew. wood, which may mean the handle or the tree.
Related Commentaries of Deuteronomy 19:5
Deuteronomy 19:5
5 As when a man goeth into the wood with his neighbour to hew wood, and his hand fetcheth a stroke with the axe to cut down the tree, and the headb slippeth from the helve, and lighteth upon his neighbour, that he die; he shall flee unto one of those cities, and live: