Screwdriver bits question

[Anna]

This is something that's stumped me for a while now. I thought I'd figure it out eventually, but at this point, I decided it's just easier to ask:

How do I determine which phillips-type bit goes with which screws? With the screws, I know that there are different sizes of the shanks that are reflected by the numbers (6, 8, 10, etc). I have several sets of screw bits, and I always end up just guessing which one to use. Most of the time, it works. But sometimes I end up ruining the screw head, not to mention some of the bits.

[LCHIEN]

I just try the bits to see which fits best...
too big and the bit won't go down into the recess, just bounce over the tops, rounding them off.
Too small and you can feel the point hit the bottom and the blades will rattle around the recess, rounding it off.
The right size, it will fit snugly, even hold the bit in place.

There are also some bits that look like philips but are not... they don't fit quite right, either.

[Slik Geek]

I just look at the screw head and can tell whether it is intended for a #1, #2 or #3 bit. If you can find (by a trial and error method or otherwise) three screws that represent these three bit sizes, then hold them side by side, you'll see that you can gauge which bit is appropriate by the length of the slots in the Phillips cross. (#3 slots are longer than #2 slots, which are longer than #1 slots). For me, this visual is all I need to determine the bit size. Other folks' brain wiring is different and may not be able to remember this, so YMMV. (It helps to have driven a zillion screws in your lifetime).

Generally, a 4-xx screw will use a #1, an 8-xx will use a #2, and #12-xx screws will use a #3. (Can't recall at the moment where the in-between sizes end up).

[Anna]

Well, thanks, guys.

One, I don't feel so bad about the trial-and-error method anymore. I thought there might be some hidden technique or method or something that I'm totally obtuse to, but it seems like taking the screw and trying the different bits is pretty much the way to do it.

Two, I'm pretty sure there are more than 3 kinds of bits. If the #1, #2 and #3 bits are the ones to use, I won't know which ones they are just by looking at my bit sets. One has at least 12 different kinds of bits (not counting the different shank lengths) and another has at least 16. I know there are torx bits and the square drives, and of course the flat heads, all of which I've used at one time or another. Those don't give me as much trouble as the phillips-types, though.

But thanks again. Maybe I should start sticking to the square-drive screws instead.

[TheRic]

I mostly go with trying the bit in the screw. I have noticed that some screws will fit a couple of bits. Or should I saw a couple of bits will fit in the same screw. The brand of bits does matter. The cheaper ones seem to try and fit more screws, but all it does is ruin the bits quicker.

Will say the name brands normally last longer than the no-name brands. Don't know if it's different metal, different hardening, etc.

[Pappy]

1, 2, and 3 are the common Phillips head sizes but there is also a #0. The Reed and Prince head is similar but the angle of the bevel on them is higher than on the Phillips. The Reed and Prince also come to a point, where the Phillips has a flat spot on the tip.

[Tom Slick]

just to confuse it a bit more there is also JIS screws. most japanese screws are JIS and are slightly different then philips. philips usually work ok in them though. motorcycles are usually JIS. (japanese industrial standard)

usually;
#2 won't fit into a #1 sized screw
#3 won't fit into a #2 sized screw
#1 fits very loosely into a #2
#2 fits ok into a #3 but you'll notice the slots in the screw are still larger then the bit.

[Slik Geek]

1, 2, and 3 are the common Phillips head sizes but there is also a #0.

Yep. I considered mentioning the #0, but since it is generally only found on tiny screws, I figured that it wasn't relevant in this context. To be complete, however, it should be mentioned.

[Anna]

I didn't know about the Prince and Reed heads. I thought they're all Phillips. How do I know if a screw uses one type or the other? Do Phillips screws have a flat portion in the middle or something? Is there a screw sampler that will show all the different kinds of screws and the bits that go with them?

[JimD]

My only good practice is to put the screw on the screwdriver tip I think fits it up close where I can see the fit before I start to drive it. When I try driving it first, I am subject to the quality of my guess. If I guessed well, all goes well. If I guessed poorly and am lucky, it starts slipping while I can still get it out and maybe I have another screw. If I look at the fit first, I eliminate the vast majority of the mess-ups.

I also have a fairly wide selection of various bits so I have a few to try. I like the reduced size #2 phillips the best. They fit pretty well unless you are way off on the angle or it isn't a #2 phillips you're trying to put in. For screw heads, I like the kind with the combination square/phillips head. I've only seen them in deck screws, however. If you use the special bit that generally comes with the screws, they drive very well. Square drive is OK and harder to mess up with than phillips but the recess is pretty small and if the driver is not in great shape, you can ruin it pretty quick.

Jim

[mschrank]

Maybe it's just the sizes I work with most often, but seems that a #2 phillips is the most common.

When I buy project screws, I only purchase square-drive (Robertson). I've only run into two sizes of these, with #2 being most common again. I do have some #1 "trim-head" screws as well. On the square drive, the difference between #1 and #2 is pretty obvious just by looking. And if you grab the wrong driver, it's apparent as soon as you place it in the head of the screw.

[rnelson0]

Actually, the correct answer is to test using someone else's drill bits

The snug fit theory is what I use. Failing that, I use the "curse at it until it goes in" theory.

[Anna]

I think I'll go ahead and buy a bag of single-size #2 bits that contractors use. I use mostly coarse-thread screws from HD for plywood and melamine projects (when I'm trying to save my confirmat screws), and I'm guessing the #2 bit will fit those. It's the miscellaneous screws that I get with kits, like for sliding bathroom organizers, etc, that always get me.

In any case, seems like everyone pretty much do the snug-fit theory (as Rob puts it), so I'll stick with that. Until someone comes along with a better theory anyway.

[Black wallnut]

The best explanation on the various bits is found on Snap-on.com. You'll have to click on each individual bit style and then enlarge each picture. Not only is there Phillips, Reed/ Prince but do not forget Pozidrive. I've seen plenty of Pozi in automotive applications.

I can tell the sizes and types just by looking, call it years of experience if you will. Same way that I can just look at an SAE or USS bolt and tell its size and thread pitch. Same way that I just know which size wrench or socket to grab. Some things you just know!