Personally, I wouldn't do it with my drill press. It's just like running the drill press under low-voltage conditions and those can be bad for the motor (e.g., cause it to overheat because of not enough cooling).
Here's a quote from the web: an induction motor operating near its rated load on 90% of nameplate voltage can be expected to have its efficiency reduced 1 to 3%, have its operating temperature increased 10 to 15% and have its running torque reduced nearly 20%.
