Of all the types of drill bits available on the market, twist drills are the most common because they can be used for cutting virtually any type of material. Other types of drill bits are specialty bits, used for only certain materials. I’ve decided to limit this list of best drill bit sets to standard “jobbers length” or standard size length twist drill bits. There are other lengths available, such as “aviation bits” which are 6 or 12 inches long. However, these are rather rare and quite costly.
Twist drills come in three basic size groups:
- Fractional drill sizes – typically from 1/64 to 1/2 inches in 1/64 inch increments. However, also available in sized up to over 1 inch.
- Letter drill sizes – used predominantly by machinists, these sizes are essential if you are going to tap threads into the hole.
- Wire gauge sizes – again, these are predominantly used by machinists.
The biggest enemy of drill bits is heat which reduces the temper of the metal and causes the cutting edge to dull quicker. When drilling holes, there are two things that you can do to reduce heat that your drill bit is creating:
- Drill at a slower speed. The general rule of thumb is that the harder the material, the slower you should drill.
- Use a cutting oil which lubricates the drill to substrate contact, reducing heat. If you don’t have an actual cutting oil, any light mineral oil will work.
Manufacturers have experimented with materials, in order to create drill bits that will last longer. This is specifically dealing with drill bits that are used to cut metals. The most common materials are:
- Low carbon steel – Although fine for working in wood and plastic, it won’t hold an edge long for metal.
- High carbon steel – These can be honed sharper and hold an edge much longer than low carbon. If overheated, they will lose their temper immediately and become dull.
- High speed steel – Is a special steel alloy, formulated for drill bits and other cutting tools. It’s much more resistant to heat than high carbon steel.
- Cobalt steel alloys – Are variations on high speed steel which contain more cobalt. This allows them to withstand temperatures up to 1000 degrees. However, they are more brittle.
- Tungsten carbide (typically called just carbide) is an extremely hard material that can cut in just about anything. Since it is expensive and very brittle, it is normally just welded to the tip of the drill bit, creating the cutting edge.
- Polycrystalline diamond – This is man-made diamond, sintered to a carbide support. These are the hardest bits, able to cut anything but they are very expensive, generally used only in industry, where taking the time to replace a drill bit might delay a production line.
In addition to the materials that the drill bit is made of, many manufacturers coat their drill bits with various materials, providing reduced friction or wear. These drill bits cannot be sharpened as the process of sharpening will remove the coating on the sharpened cutting edge:
- Black oxide – The least expensive of coatings. This provides for heat resistance, lubricity and corrosion resistance.
- Titanium nitride (TiN) – A hard ceramic material. When used to coat a high speed steel bit, it prolongs the life by two or three times.
- Titanium aluminum nitride (TiAIN) – Is considered superior to TiN, with the ability to extend a drill bit’s life up to five times.
- Titanium carbon nitride (TiCN) – Like TiAIN, can extend the drill bit’s life up to five times.
- Diamond powder – This is the hardest bit coating, creating an abrasive bit, rather than a cutting bit. These bits are used for cutting tile, stone and other very hard materials. Due to the heat generated, it is typical to spray water onto the cutting point, in order to prevent damage to it.
For your reference, some of the other types of drill bits available are:
- Step drill bits – Designed to create a hole with a counterbore or countersink
- Unibit – Designed to cut a number of different sized holes in sheet metal
- Hole saw – For cutting larger holes in sheet goods
- Center and spotting drills – Used for machining, to create a starter hole in an exact location or create a place for a center on a lathe
- Core drill bit – For enlarging existing holes, such as enlarging a cast hole in a metal casting
- Countersink bit – For countersinking
- Ejector bit – A hollow design so that water can be run into the hole to remove chips
- Gun drill bit – Designed to drill deep holes, extremely straight for guns; they come up to 8” in diameter and over 20’ long
- Left-hand bit – Used predominantly in specialize operations with CNC equipment
- Spade bits – For boring holes in wood
- Straight fluted bit – Used for boring in copper or brass, so that the bit doesn’t drag and dig in
- Brad point bit – For wood boring, the brad point provides an exact center location
- Forstner bit – For boring precise, flat bottomed holes in wood, can go up to 4” in diameter
- Auger bits – For boring deep holes quickly
- Masonry bit – Designed more to chip out the masonry, with a flute for removing the dust
Just a quick safety note: Always wear eye protection when drilling. Chips, dust and flakes can be thrown off by the bit, causing damage to the eyes or blindness.
If you have lots of drilling to do, this set gives you every size you might want. I especially like split-point bits like these, to help prevent the bits from skating over the work surface. Read Full Review
I've picked this set for #1 more for versatility than anything else. With this 115 piece set, you get 29 fractional sizes (1/16 to 1/2 inch by 64ths), 26 letter sizes (A to Z) and 60 numbered wire-gauge sizes (1 to 60). They are cobalt for drilling the hardest materials. The 135 degree tips are aggressive enough for fast cutting. They are also split-point, which helps keeps the bit from skating. Everything packaged together in a nice metal indexed storage case.
What makes this set really stand out is that all the drill bits from 9/64 inches on up have a built-in pilot drill. The smaller ones are split point and what this does for you is save you time by eliminating the need to drill a separate pilot hole and then switch drill bits. Read Full Review
What makes this set really stand out is that all the drill bits from 9/64 inches on up have a built-in pilot drill. The smaller ones are split point. What this does for you is save you time, by eliminating the need to drill a separate pilot hole and then switch drill bits. With the built-in pilot bit, you start out as if you were using a 1/8 inch drill bit to create your pilot hole, and then the bit steps up to the finished size.
Bits have a no-spin shank, which essentially means that they have three flats ground on them so that the jaws of your chuck can make positive contact on the flats. This is an old trick that I and many others have used for years, especially when drilling in metal with larger bits. Size markings are farther up the bit than normal too, ensuring that they won't get erased by the drill chuck.
The set comes in a new type of index case, with the various index pockets acting like pages in a book, rather than tipping up one after the other. I think this makes the index easier to work with and find the bit you want. About the only bad thing I could say about this set is it isn't coated with any of the exotic coatings used to reduce friction. But then, if you're used to using cutting oil when drilling in metal, that's not really much of a loss.
For quality, I'd have to go with Bosch. All their blades and bits are of excellent quality, well worth the money. This set has all fractional sizes from 1/64 to 1/2 of an inch. They are split-point to avoid skating. Read Full Review
Bosch is known for the quality of their power tools, blades and bits. Even if you don't have Bosch power tools, it's well worth investing in their blades and bits. This 29 piece set provides all the fractional sizes from 1/64 to 1/2 inches by 1/64 inch increments, a standard for drill bit sets of this type. Like most of the bits on this list, they are Cobalt, making them harder for drilling the hardest materials. Like my #1 pick, they have 135 degree spit-point tips for rapid cutting and no skating.
This is Irwin's standard 29 piece set. The shanks on the bits over 3/8 inches in size are stepped down to 3/8 of an inch, so you can fit them in a 3/8 of an inch drill chuck. They are 5 percent cobalt, with split-points, like the others we've shown. Read Full Review
This is the industry standard 29 piece set. It covers all fractional sizes from 1/16 of an inch through 1/2 of an inch by 64ths. All the bits above 3/8 of an inch have a 3/8 inch shank size so they will fit into a 3/8 of an inch drill chuck. The 135 degree split point is an advantage for self starting and the M35 designation means that these bits contain 5 percent cobalt, making them much harder than high speed steel or titanium coated high speed steel. They can be sharpened and retain their advantage because the cobalt is in the mix not a coating.
Craftsman has made this set with cobalt for both the finish and the material. The shanks on sizes over 3/8 of an inch are reduced to fit a 3/8 of an inch drill chuck. I especially like the plastic case, which is much easier to work with than the standard metal drill index. Read Full Review
This set is specified by Craftsman as having cobalt for both the finish and the material. The set has reduced shanks over 3/8 of an inch so even in the larger sizes will fit a normal 3/8 of an inch drill chuck. It is the industry standard 29 piece set covering the range of 1/16 of an inch to 1/2 an inch by 1/64 of an inch. The bits are ground to a split point for cleaner starting with less bouncing and wandering around. Craftsman's case is a clear sided plastic case, instead of the standard metal one, making it easier to see what you've got in your set.