If the axe is dull and the blade unsharpened, more strength must be exerted, but skill produces success.
The scope of these verses is to keep subjects loyal and dutiful to the government. In Solomon's reign the people were very rich, and lived in prosperity, which perhaps made them proud and petulant, and when the taxes were high, though they had enough to pay them with, it is probable that many conducted themselves insolently towards the government and threatened to rebel.
Commenting on Ecclesiastes 10:4-11
If the iron be blunt,.... With which a man cleaves wood: the axe, made of iron: and he do not whet the edge; with some proper instrument to make it sharper, that it may cut the more easily; then must he put to more strength; he must give a greater blow, strike the harder, and use more force; and yet it may not be sufficient...
iron . . . blunt--in "cleaving wood" (Ecc 10:9), answering to the "fool set in dignity" (Ecc 10:6), who wants sharpness. More force has then to be used in both cases; but "force" without judgment "endangers" one's self. Translate, "If one hath blunted his iron" [MAURER]. The preference of rash to judicious counsellors, which entailed the pushing of matters by force, proved to be the "hurt" of Rehoboam (1Ki. 12:1-33).