I have a 3/8 hand-held drill and that's pretty much all I need for my projects. But now I have a project where I have to insert large dowels, and they will need a 7/16" hole. I don't have that size bit, but before I rush out and buy one only to find that it won't fit my 3/8" drill, I want to know if there are adaptors or other tricks I can use to make it fit.
There are bits with shanks ground down to 1/4", 3/8", 1/2" dimeters to fit chucks. They may need to be special ordered and may be expensive. I have several but I inherited a bunch of bits so I don't know what they cost. I have also ground 3 flats on shanks when they were a little too large for the chuck ( assuming you have a 3 nib(?) chuck).
Since this is on "home improvement" and you are mentioning dowels and a handheld drill, I assume you are working in wood.
Another answer has suggested searching "reduced shank drill", when I tried this I got mostly twist drills. AIUI twist drills are primerally intended for drilling metal and while they can be used on wood, another type of bit is likely to be more appropriate for drilling large holes in wood.
My understanding is there are three main options for drilling large holes in wood. In my experience all of them will come with shanks small enough to fit in a standard drill, but I'm in the UK where a standard drill can take a 10mm shank, I don't know what things are like in the USA.
- Spade bits, these are the cheap and rough option for moderate size holes.
- Forstner bits, these are the cleaner and more expensive option for moderate size holes.
- Holesaws, these are the best option for really big holes because they do less cutting work then other tools. However removing the plug of waste from the holesaw can be annoying, depth of cut is limited, and they can't drill a blind hole (though they could be used to define the edge of a blind hole before removing the waste with other tools).