I am building a workbench where I'm using 2x4s for the frame. I need to join 2x4 in a T configuration. The instructions say to use 3'' drywall screws. I went to Home Depot, and got the Grip Rite #9 x 3'' screws that look like this: https://pasteboard.co/GziIbad.jpg

How do you drive these in? I tried:

  1. Drilling a 1/8'' hole but the drill bit is only about 2'' long
  2. Used an impact driver.

In both cases, only the threaded (about 2'') part of the screw went into the wood. The non-thread part is protruding. Is the rest supposed to be hammered or what? Or maybe I got the wrong screws. Are there 3'' drywall screws that are totally threaded? For example, the 1 5/8'' ones are. Any suggestions are appreciated.

  • An impact driver, if strong enough, and you are using the proper bit for the screw so it does not "cam out" will drive those screws. What impact driver are you using? Having threads all the way up will not matter. – Jack Jul 4 '17 at 1:09
  • Thanks. I'm using the Dewalt 20V impact driver: lowes.com/pd/…. I'll try changing the bit screw. I believe it was 'camming' out. – user4979733 Jul 4 '17 at 1:24

You need to drill three operations.

  1. The 2x4 piece being fastened. It needs a clearance hole drilled all the way through that allows that #9 sized screw to drop in. So the hole diameter needs to be just large enough as the greatest outside diameter of the screw. That may be the threaded part or the non-threaded part could be larger in diameter.
  2. The clearance holes may want to be counter sunk slightly to allow the heads to come flush with the surface of the piece being fastened. You do this with a counter sink bit in your drill. With 3" screws you will need to be careful to not counter sink too far because your total thickness of two 2x4's is 3" and too deep of countersink will allow the screw to come through on the opposite side.
  3. Piece being fastened to. This part will need to have pilot holes drilled. The pilot hole diameter needs to be less than the outer thread diameter on the screw but the same size or a tiny bit larger than the inner diameter of the screw thread. This is important because with fat screws like #9's it would be possible to split the lumber.

Additional hints:

a) Rub the threads of the screw on a bar of soft soap and it will make driving them in much easier.

b) Consider using 2.5" screws instead so you have less chance of them going all the way through.

c) Consider using deck screws instead that have an alternate drive slot instead of the Philips. A square drive has much less chance of stripping out when driving large screws.

d) Drill your clearance holes in the piece to be fastened first. Then clamp that piece to the part that it fastens to. This will allow you to use the clearance holes as a guide as to where the pilot holes have to go in the fastened to piece. Make sure the pilot holes are at least as deep as the screw will penetrate. For an inexpensive type 2x4 type frame there really is no problem with drilling the pilot holes all the way through. If the pilot drill bit is not long enough you may have to unclamp the pieces to complete drilling the pilot holes.

  • Thank you for the very useful tips. I will try some of these techniques. For now, I did two things. 1) I drilled a bigger pilot hole (11/64'' instead of 1/8'') and 2) switched the drive bit so there is no slippage. I was testing on a small block and I'm able to drive the screw with significant ease. – user4979733 Jul 4 '17 at 2:02
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    Drywall screws are designed for holding drywall, not fastening lumber to lumber. Deck screws are what you need; they are both stronger and easier to drive. There is a brand of deck screw which accepts either Phillips or square drive, and a special driver (pale blue color) is included in each box which is a combination of Phillips and square drive. These really drive the deck screws. – Jim Stewart Jul 4 '17 at 3:10
  • Any good deck screw will be adequate. I avoid the gold screws sold at HD like the plague. Their generic coated deck screws are fine. Spax and GRK are high-end. Drywall screws are brittle and prone to breaking in applications like this. – Aloysius Defenestrate Jul 4 '17 at 17:09

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