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.

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  • 9
    If this is for drilling in wood, there are spade or fostner bits that will make large holes with a small shaft that will fit in a 3/8 drill. There are also bits with the shaft stepped down to fit 3/8 drills if you want a regular bit. Just buy bits for 3/8 drills.
    – crip659
    May 13 at 21:14
  • Just bought a 28mm bit with 1/4" hex shank for fitting dowels…
    – Solar Mike
    May 13 at 22:43

2 Answers 2


You can find reduced shank drill bits that have 3/8" size shanks for drills like yours that go up to sizes up to at least 1/2" and more. I have several drill sets that include these.

You can find these almost everywhere. Check online with this search phrase "reduced shank drill bits".

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  • Yup, I have a set that looks very much like your second picture--a whole range of sizes. I think the set was only like 2x or 3x the price of an individual bit. Ordinary item at the local big box hardware store. May 15 at 3:11

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).

  • 5
    Doubt that 3/8 sized shanks need special order or expensive. Even most cheap bit kits for 3/8 drills will have the larger bits sized to fit. 3/8 drills are quite common.
    – crip659
    May 13 at 22:28

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