Plunging oil prices have hit Caterpillar hard. Image source: Company Year in Review 2015 presentationCaterpillar's (NYSE: CAT) first-quarter results were nothing short of a disaster. From profits to sales to orders to guidance, everything tumbled. While investors were hoping for some relief in the wake of the recent rally in prices of metals and oil, Caterpillar confirmed that recoveries in commodities prices don't translate into higher revenue on its end until spending in those industries picks up.