Tapered vs. Straight Drill Bits - FineWoodworking

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.

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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.

Link to KunXu Drill Tools

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.

For more information, please visit 7° Tapered Drill Bits.

Correct. If you want to use a traditional wood screw and have it go in easily without ruining the head, esp. one with a slotted flat head, you have to pre-drill three times or use one of those sets, and use a screwdriver that exactly matches the screw slot. Many people also put lubricant like wax on the threads. Without these precautions you can mar or destroy the slot, or the screw will not hold.

It is not actually necessary to use a tapered bit - some sets are made with straight ones. Usually these sets are made so that you can either countersink or counterbore just by going deeper.

I believe wood screws are not used much now except for fine woodworking and wooden boats, because they need too much time and care to drive a lot of them in commercial use. However some people believe only a slotted head is attractive when exposed on hinges and such. True. Wood screws are both worthless and dangerous without a proper pilot. Worthless because of failure and rework. Dangerous because they can damage or even destroy your project piece.

The most common failure is stress cracking of the wood. Hardwood or softwood, most will crack eventually under the stress of an unpiloted screw. The second failure is at the head from over-torqueing. Either the head is deformed or broken. The third and most catastrophic failure is a broken shaft. This failure is most common on brass screws.

When I make repro furniture, I like to use brass screws for hinges as noted. The trouble is that most modern brass screws are made from cheap alloys and are exceedingly soft. I take special care drilling proper multistep pilots and then install exact sized steel woodscrews first. Then I remove the steel screws and install LUBRICATED brass screws. It works well MOST of the time.