You need a bit that will fit the drill. Assuming that he has the most common drill, it will take a 3/8 shank. You will have a hard time finding a normal drill bit that will be 1" and fit that shank. HD and Lowes will probably point you to the 1" wood drill bits.
You may find that you need a smaller drill bit, and a Unibit to get 1".
http://www.ebay.com/itm/Irwin-1-1-8-...item3cbcd317b8






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