Use a bi-metal hole saw. The skin of a steel door is only a few hundredths of an inch thick. On the side, where you mortise in the hinges and the latch, you should find plenty of wood.
I'm replacing 3 windows as part of a renovation project. This is strictly a DIY project. I have never done this before. My question for anyone who has any experience in this area is: which is best (wood or vinyl) for replacement windows) Cost is a major consideration in this project. I would also like info. on web sites that might have step by step instructions for DIY projects such as this. I am a sinle mom living from paycheck to paycheck. I am going to enter my project in a BH&G contest. Any info. or advise is greatly appreciated.Read More