This chart gives the pilot hole needed for wood screws.
A #8 requires 5/32 or 7/64. Taper vs Straight bit.
5/32 is 10/64. They are saying a tapered bit makes a hole 3/64 larger.
Probably doesn’t make any difference. 
The screw will work fine even with a 1/8 (8/64) pilot hole.
How do you know if a random drill bit in your toolbox is tapered or straight?
Look at it?
Does it look any different?
I’ve never paid any attention to drill bits.
Grab one at HD, pay for it, and take it home.
I seem to recall tapered on the package. But, I’m not positive.
If it’s not obvious, lay it flat and lay a flat file or steel rule or something against the top surface, that will extend any taper to a greater distance. If you’re really paranoid, drill a hole in a piece of wood then see if the other end will fit in the hole.
Ok.
I didn’t realize until today that one drill bit is any different than another.
I know it really doesn’t matter. I’ve started wood screws using a 16d nail to make a hole. It’s more work, but they’ll screw right into a pine stud.
I’ll look at some of my old drill bits. I’m curious now.
I’ve watched C-beams glitter in the dark near the Tannhäuser Gate.
I don’t believe you.
The tapered drill bits I have seen for wood screws are tapered enough that it is obvious from a quick glance. They also often had attachments for making a countersink allowing the screw heads to not stick out abouve the surface of the wood.
Tapered may be something new.
I think my older bits are just plain, straight bits.
The package says, Twist bits.
The shank of a screw doesn’t have threads. It can sometimes cause problems in hard wood. I guess having a tapered hole would make it easier.
Gazpacho nailed it. They are made to match the taper of a wood screw.
GaryM
And for all practical purposes, you really aren’t going to see any. I’ve been machining and woodworking for 50 years and have not come across one - except for those complex pilot/body/countersink drills. Some of those replace the pilot/body combo with a tapered bit.
The only ones I see are places like Rockler for serious woodworkers.
Dennis
There are tapered bits? When did this start?
My bits are bulbous, also tapered.
They are actually real old school, going back to when you had to place every screw by hand. Tapered awls were used for small holes. Tapered bits were available, but probably only used by cabinet makers. With power tools there is no real need for one unless you are obsessed with perfection.
The only ones generally available from major tooling companies are for tapered reamers for metalworking and few people use those either. We just step drill the hole.
I just checked 3 of the major industrial supply houses, McMaster-Carr, Grainger and Production Tool. Only Grainger carries one. One. And it is in clearance.
Dennis
I’m surprised the pilot hole chart had a column for a bit that most homeowners don’t have.
It needlessly complicates the information.
I’ve fit a set for screw sizes 6 through 12 with the countersink or plug option. I’ve only used them on hardwood such as oak or maple. Not used them years however.
GaryM
The tapered ones are pretty visibly obviously so (pic) - if you had some you’d know it.
More generally speaking, for making small measurements nowadays you can buy a digital caliper for 20 bucks or so (link)
Many moons ago I made a lot of stuff with wood screws ( big ones ) and we had a full set of flat looking drill bits that matched wood tapered counter sunk screws.
We had screws that the upper part was tapered and smooth and the lower part was a smaller dia. so that the screw would cut threads and not just crunch the wood. The smooth part matched the thickness of the outside board and the threads engaged the lower wood. These screws were designed to be removed and reinserted and they were initially put in with stuff like Lubricant to help them actually make threads.
We took these tanks apart many times, all by hand for good control and they worked again & again. It was like they had threads. ( they actually did. )
That pic is very helpful. I don’t have any bits like that.
Thank you.
If you put the bit on a flat surface and roll it - a straight one will roll straight and a tapered one will roll in a curve.
