How to Select Drill Bit Sizes

Written by wade shaddy | 13/05/2017
How to Select Drill Bit Sizes
Selecting the right bit is important. (Stockbyte/Stockbyte/Getty Images)

Drill bit sizing is important. When drilling for wood screw placement, the drill bit must be slightly larger than the shank of the screw. If the hole is too small, the screw can crack the wood. Too big, and it weakens the screw function. The drill bit should be approximately the same size as the screw threads. Take a few minutes and select the correct size bit for the job.

Place a screw inside the jaws of an adjustable wrench. Close the jaws slightly until they touch both sides of the screw threads.

Take the screw out of the jaws. Insert drill bits between the jaws until you find one that fits as tightly as the screw did.

Place the bit into the drill. Drill a hole in a test piece of wood.

Insert the screw into the hole. Push and pull it up and down. It should fit snugly, but should not get stuck in the hole.

Check the length of the screw. If it's more than 3 inches long, you'll need an extra long bit.


Use the same method to find the correct bit size for larger bolts.

Tips and warnings

  • Use the same method to find the correct bit size for larger bolts.

Things you need

  • Adjustable wrench
  • Drill bit assortment
  • Cordless drill

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