Farming with swords isn't a good idea. They move slower then axes, so in the long run axes are cheaper. Additionally you are much more endanger of getting spiked.
No need to pay for research costs, and for one farming party you need minimum 5 swords or 3 axes. 3 axes cost 180 wood, 5 swords cost 150 wood. More than balances out the extra time each run, imo.
As for getting spiked, sword spikes will harm axe users just as much as sword users, spear spikes will be laughed off just as much by both. Splitting with swords instead of axes also means you split earlier, meaning you are "safe(r)" from spiking earlier, as hitting a spike with only a farming party is far less harmful than hitting it with your full farming force while you're trying to save up for axe research.