What size drill bit to use for predrilling?

I am connecting two 2 x 4s together withe drywall screws.

I am using 2.5" screws.

I will be going through the entire 1.5" of the first 2x4 and 1" of the second 2x4.

My question is

a) what size diamteter drill bit should i use to predrill

b) how far deep should I predrill?

Any general rules, tips, tricks that you go for when predrilling?

thanks

17 Answers

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  • Zenkai
    Lv 6
    1 decade ago
    Best Answer

    if they are self tapping screws you shouldn't have to predrill. it doesnt matter the length of the screw it is the diamater. Usually you got about 1/16 less than the diameter of the screw for small screws

  • 3 years ago

    Sheetrock Drill Bit

  • 1 decade ago

    I have always used a bit just a little smaller ..or one size down from the diameter of the screw...or smaller...you do want the screw to bite a little in the hole drilled..if you are using 2.5" screws I would drill no more than 2 inches deep...maybe even a bit shy of 2 inches..you want a good bite with those end threads...hope this helps,you will no what sizes hole and how deep you want to go after a few screws ,you'll feel it .

  • Anonymous
    4 years ago

    This Site Might Help You.

    RE:

    What size drill bit to use for predrilling?

    I am connecting two 2 x 4s together withe drywall screws.

    I am using 2.5" screws.

    I will be going through the entire 1.5" of the first 2x4 and 1" of the second 2x4.

    My question is

    a) what size diamteter drill bit should i use to predrill

    b) how far deep should I...

    Source(s): size drill bit predrilling: https://tr.im/kyg3R
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  • 1 decade ago

    I always hold the bit up in front of the screw, and look past the bit at the screw. If the bit covers the core of the screw but I can still see the spirals, that is the right size. If the bit is smaller than the core of the screw, it won't help enough, and if it does not leave enough of the spirals showing, it will be too big and the screw won't hold good. This method will work for any size screw you have. As for length, I always drill about 1/4 " to 3/8" shorter than the screw. I like to use painters blue tape on the bit for a drill stop, or sometimes a magic marker line on the bit works too. Hope this helps!

  • 1 decade ago

    I use a drill 1/2 the diameter of the screw. Drywall screws are not tapered like wood screws. I would drill through the first 2x and no drill in the other. Be sure to clamp the pieces together before driving the screw.

  • 1 decade ago

    Just make sure the diameter of the drill bit is slightly smaller than the thread size of the screw and you'll be fine. Clamp the two boards together so they won't move in the process and drill through.

  • 1 decade ago

    If your using drywall screws you don't need to predrill. You only need to predrill when using hard wood like oak. Then you would drill a 1/16 smaller than the outside diameter of the screw.

    Tool & die maker 35 yrs

  • 4 years ago

    If you are planning to start on your woodworking project, this isn't something you should use, it's something that you would be insane not to. Go here https://tr.im/QwNZe

    Truth is, I've been a carpenter for almost 36 years, and I haven't found anything like this for less than 10's of thousands of dollars.

  • 1 decade ago

    Use a drill bit one size smaller than the hole you need. Mark depth of fixture - nail/screw - depth with tape. Go that deep and no further

  • 1 decade ago

    if you are using 2.5" screws, i'd go with a 3/8" drill bit, but i've found it's better to not pre-drill as deep as the screw length--i.e. i'd pre drill about 2"-21/4" for a 2.5" screw...a nice way to determing pre drilling depth is to either set the bit to the depth you want in the drill, or, if it's a longer bit, wrap a piece of tape around the bit at the depth you wish, so when you are drilling you can tell when you get to the desired depth......or you could find a military base and ask a drill sergeant what you should do....

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