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I just bought my first impact driver and I was wondering am I suppose to still pre-drill holes with a bit with my regular drill before using the impact driver when going through woods?

I use to always pre-drill the hole then put the screw in with my drill, so now that I have an impact driver can I just drill the screw directly into the wood or am I suppose to still pre-drill and the impact driver will just make it easier going into the pre-drilled hole?

Thanks

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3 Answers 3

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If the wood is prone to splitting, it'll still split when you don't drill pilot holes, impact drill or not.

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  • 1
    What if it's not prone to splitting, like a 2x4? (or are 2x4's prone to splitting as well?)
    – BlueRaja - Danny Pflughoeft
    Jul 4, 2015 at 18:21
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    I've split plenty of pine 2x4's. New pine is very prone to splitting. If you keep the screw diameter small enough, and the length short enough, you can get away with out pilot holes.
    – Wayfaring Stranger
    Jul 4, 2015 at 18:53
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    There are some times when it's not feasible to pre-drill holes. (I.e. building a deck, and other large-scale projects.) In those cases you just start throwing screws in and hope for the best.
    – Der Kommissar
    Jul 4, 2015 at 20:15
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    @WayfaringStranger Thanks for the answer, now when I pre-drill should I use my impact driver to pre-drill or should I use my normal drill?
    – Greenhoe
    Jul 5, 2015 at 1:37
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    And there are a variety of self-drilling screws which make splitting unlikely in many woods (but not dense hardwoods such as oak).
    – bib
    Jul 5, 2015 at 22:20
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Pre-drilling is not just about wood-splitting. It fundamentally changes the nature of the joint.

Take the example of screwing decking to joists. If you were to pre-drill the deck board so the hole was WIDER than the screw but the screw is allowed to bite into the joist. The joint becomes much like a nut-and-bolt where the entire joint is held in place by tension between the screw head and the tip of the screw in the joist. This tension pulls the deck board really hard and uses the screw in the way that it's strongest - it's tensile strength.

When you don't pre-drill, this tension is lost and the joint is held together in a completely different way.

In practice, joints will not normally fail if accomplished using either method - but the pre-drill method will make a stronger joint for a given screw size.

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The reason the hole is drilled is to remove excess material so that when the screw bites in, it does not rip the wood (or whatever) apart. It's simple physics. When the screw does in, if there is no hole, then the wood volume occupied by the shank of the screw is displaced. Where do you think that wood goes? Outer space?

Forcing screws into wood using an impact driver is something hack roofers do (except when they are working on their own house, of course).

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  • Thanks for the answer, now when I pre-drill should I use my impact driver to pre-drill or should I use my normal drill?
    – Greenhoe
    Jul 5, 2015 at 1:39
  • A regular drill is all you need. Impact drivers are for driving screws very quickly, not drilling holes.
    – Tyler Durden
    Jul 5, 2015 at 1:56

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