Almost every drilling application requires a different type of drill bit. Twist bits are probably most familiar to you, but there are many types and not every bit is created equal. The material that drill bits are made from and their design determine what you can drill with them, be it hardwood, softwood, other soft materials, concrete or metal etc.
It depends on what you need to do. Drilling into cement requires a special drill bit. You can drill pilot holes for screws or bore a counter-sink hole so the screw’s head is flush with the material you drill through.
You may find this drill-bit-guide useful so you can reach for the right drill bit for the job. Even if you’ve drilled thousands of holes into various types of materials during your DIY endeavours, a guide can still come in handy when you come across something new.
Pre-Drilling
There are several basic reasons why you may need to predrill a hole.
In order to install a fastener, pre-drilling is necessary. Pre-drilling is essential for many reasons, among which I’ve listed a few below:
- So you don’t split the wood with a screw,
- The material is too hard,
- You want to create a hole for something to pass through,
- To get high accuracy, you pre-drill hole to provide a guide,
- To counter sink a screw below the work surface.
A general guide is that the hole should be about 3/4’s the size of the fastener you plan on using. Some people think that pre-drilling is necessary only for screws, but you can also pre-drill for nails, depending on the material you’re putting them into.
Consider the task of a framing carpenter. They could safely hammer a nail into pine 2 x 4s without having to pre-drill, because the wood is soft enough for them to get away with it.
But imagine you’re installing pressure-treated deck boards. Pre-drilling is usually done in this situation, but only at the end of the board, within 2 inches. Why you may ask? The end grain tends to split, exposing the inside wood fibers and possibly causing premature rot. It also looks terrible!
Pre Drilling For Toggle Bolts
Drilling holes for toggle bolts occurs in all kinds of materials. Metal or ceramic tiles require a special bit for drilling as does concrete or metal. You can use this drill-bit-guide table below to determine what size drill bit you may need for a given application.
Make sure you purchase the correct drill bit size for special fasteners, and a piece of free advice, check the package for a drill bit guide before leaving the store. It’s better to purchase the right drill bit then, then have to go back later!
Pre-Drill Bit Sizes Table
| ScrewSizes | CounterBore Diameter for Screw Head | ClearanceHole for Screw Shank | PilotHole (hard-wood) | PilotHole (soft-wood) |
| #1 | 9/64 or.146 | 5/64 | 3/64 | 1/32 |
| #2 | 1/4 | 3/32 | 3/64 | 3/32 |
| #3 | 1/4 | 7/64 | 1/16 | 3/64 |
| #4 | 1/4 | 1/8 | 1/16 | 3/64 |
| #5 | 1/4 | 1/8 | 5/64 | 1/16 |
| #6 | 5/16 | 9/64 | 3/32 | 5/64 |
| #7 | 5/16 | 5/32 | 3/32 | 5/64 |
| #8 | 3/8 | 11/64 | 1/8 | 3/32 |
| #9 | 3/8 | 11/64 | 1/8 | 3/32 |
| #10 | 3/8 | 3/16 | 1/8 | 7/64 |
| #11 | 1/2 | 3/16 | 5/32 | 9/64 |
| #12 | 1/2 | 7/32 | 9/64 | 1/8 |
Pre Drilling For Nails
Generally speaking, you should pre-drill holes for screws or nails installed near the edge of a board. So the obvious cases are when installing decking boards as mentioned above or if you’re installing some nice trim work around a door, window or baseboard. For trimming installation, if hammered into the molding close to the edge, you will need to predrill for the small 4d or 6d nails. Decorative trim can crack and split, rendering it no longer decorative.. so don’t risk it!
Drill-Bit-Guide For Toggle Bolts
Toggle bolts come with detailed instructions on what size drill bit to use. Below you will find a drill-bit guide for the most common toggle sizes.
When using toggle bolts, you should be aware that you cannot use them if the hole will be drilled into a wall stud. To find studs before drilling for toggle bolts, use a stud finder.
The good thing about finding a stud is that you can drill directly into it, eliminating the need for a toggle bolt in the first place.
In the absence of a stud finder, drill a 1 1/2-inch deep hole where you plan to place the toggle. Straighten out the paper clip. Stick it into the wall.
In that case, you are not drilling in a stud and are free to drill the bigger hole. You’re more than likely in a wall stud if you can’t stick the paper clip in further.
Types of Drill Bits
To state the obvious, drill bits are cutting tools that create round holes. Upon insertion into a drill, these drill bits spin at high speeds to bore a hole in the material being drilled.
Twist Bits
Twist Bits are a type of drill bit used for general-purpose drilling. Titanium drill bits are a minimum option that I buy because they can be used on many surfaces ranging from softwood to hard metal. Additionally, you can purchase Cobalt bits, which are extremely hard.
Punches are used to create dents for twist bits when cutting metal. As a result, this “dent” serves as a drill-bit guide.
Brad-Point Bits
A Brad-Point-Bit is a variation of a twist-bit used to cut holes in wood, with a central “brad” point to ensure accurate positioning. Bits with brad-points are more expensive, but they create cleaner holes in most cases, and the brad in the center makes it easier to place the bit accurately.
Tapered With Counter Bore
For predrilling holes with a counterbore at the top, the bits are tapped with the length of the counterbore. By mimicking the screw’s profile, the tapered cut ensures a stronger hold in wood. Screw heads can be flush with works surfaces because of the counterbore.
Carbide Tip Masonry Bit
Concrete, brick, and masonry materials can be cut with the help of carbide-tipped twist bits. Typically, this bit is used with a hammer drill, which both rotates and hammers the bit into the workpiece. By hammering the drill bit, the drill bit breaks up the material at the front while the fluted body of the bit carries the dust away.
Forstner Bits
Benjamin Forstner invented the Forstner Bits, which are great for boring precise flat bottom holes in wood. They have been useful for making holes for inlaying coins and other things. A block of wood can either be cut on the edge or have holes overlapping. Since they require more force to drive into wood, they are best used in a drill press, but you can also use a hand drill (depending on the size of the bit).
There is also a small hole in the bottom of these bits due to the center point, which guides it into the cut. Essentially a twist-bit for cutting holes in wood, it has a center “brad” to allow for accurate positioning and prevent it from skating. Despite the higher price, brad-point bits create a cleaner hole and have the advantage of being easy to place on layout lines because of the center brad.
Screw-Point Boring Bit
A screw-point borer bit, also known as an auger bit, is used to bore larger holes in wood. Those are the tools electricians use to drill large holes through framing so that they can run electrical wires. With a self-feeding screw point, the bit will drive into the wood as you drill, and the flutes remove waste material in the process.
Spade Bits
For rougher wood boring, spade bits are used. They do tend to leave splinter marks on the material when exiting it, so don’t use them where you want a fine finish where the bit exits the back of the wood you are drilling.
Hole Saws
A hole saw consists of a metal cylinder mounted on an arbor with a pilot bit. To cut holes in wood, these bit can have teeth for a cutting edge, or they can have industrial diamonds embedded for cutting granite countertop holes, for example. The one shown is for cutting wood with a pilot bit. A diamond bit does not contain a pilot bit. The bit is used in portable drills. The diameter ranges between 1/4 inch and 5 inches. Those with embedded industrial diamonds can be even larger.
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