A recent change in Iowa’s tax code spared Mark Chelgren’s machine shop, welding company and wheelchair-parts plant from paying sales tax when buying certain supplies such as saws and cutting fluid. The change passed by the state Legislature last year wasn’t just good for Chelgren’s businesses. It was brought about in part by Chelgren himself. The Iowa state senator championed the tax break for manufacturing purchases as part of his work at the Statehouse in Des Moines. Chelgren, R-Ottumwa, isn’t the only state lawmaker doing his outside interests a favor.