Hey all! Amateur woodworker here in need of some guidance. I’m not sure if I should be using a tapered or straight bit and for the life of me can’t find an answer. I have a handy dandy Wood Screw Pilot Hole Size chart that tells me for a #8 wood screw pilot hole I should use a 11/64 tapered bit or a 1/8 straight bit for hard wood and 5/32 tapered bit or a 7/64 straight bit for soft wood.
<!—-><!—-> <!—->
I don’t understand the purpose of a tapered bit. I have an 11/64 tapered bit but when I hold it next to the screw, the bit is wider at the end of the taper than my #8 2 ½ screw. How can this work? It would make the pilot hole larger than the screw.
<!—-> <!—->
I’m going to guess and presume that the tapered bit would correspond with a tapered screw and that I should use a straight bit for my pilot holes.
<!—->
Which leads me to my next question. Are tapered screws used for specific purposes or is it just a matter of preference over straight screws?
<!—->
Please advise. Thanks in advance.
Edited 6/15/2006 9:25 pm ET by rfromp
Replies
Is your screw a actual wood screw--with the straight, unthreaded shank before the threading starts? If so, the idea of the tapered bit is to provide clearance for the shank. That makes it easier for the board under the head to tighten up to the wood with the threads biting. Sometimes, you see recommendations for one drill bit size for the threaded part, with a larger drill for the shank.
Hey Steve. Yes it has about a 1/2" of straight unthreaded shank before the threading starts. I'm also using a 3/8" countersink and my concern is that with the pilot hole so wide will the screw drive farther into the wood than it should?
Another quick question. How deep should the pilot hole go? Should it be the same as the length of the screw? Thanks!
Yes
It will only screw as far as the shoulder on the countersink, unless you have very soft wood and an overly aggressive driver. That's why there is a clutch on the cordless drill/drivers.
Thanks for the help, I just might be ready to build something now, look out!
This forum post is now archived. Commenting has been disabled