Virtually all best drill bits are designed to spin clockwise, which isn’t a problem on a drill press, but many hand drivers are reversible, so if it’s spinning but not cutting, make sure you’re going the right direction. 3/8 is a good general purpose size, and most large bits have reduced shafts to fit in a 3/8 chuck.
The bit should stay straight as it spins and not wobble or turn into a blurry cone. Let the tool do most of the work, applying steady pressure directly parallel to the bit.
Mind the speed of the drill on hard materials with large bits which can heat to the point where it will stop cutting and can burn, melt, or otherwise damage what you’re drilling. It’s impossible to go too slow to be safe, but most drills don’t provide much power at low speeds.
A good rule of thumb is: If it starts spitting out smoke or discolored chips, slow down. Use cutting oil when drilling metal, which will not only lubricates and cool the bit, but help remove chips.
You won’t typically need more than a few drops per hole, and it will dramatically improve the life of the bit. It has a pointy end and a spiral groove (called a flute) to help carry chaff out of the hole.
They’re so popular because they work in a wide range of materials and come in sizes from a fraction of a millimeter up to multiple inches. Cobalt steel bits are heat-resistant and wonderful for drilling hard metals, though they’re brittle and should be handled carefully.
Black oxide mostly lubricates and prevents rust, while titanium coatings improve the hardness and heat resistance. However, the coatings are thin and once they’ve worn off you’re left with an ordinary bit.
Sharpening them just removes this coating, and they’ll never get a return to their original performance. Spade points are the most common and require the bit to be pressed into the material before it starts to cut.
When drilling deep holes in soft materials be sure to occasionally pull the bit out and clear the flutes. Small flutes mean they can fill with chaff when cutting soft material.
They require more torque than a twist bit, so if you’re using them with a hand drill be sure to hold on tight. Their simple construction means they’re easy to sharpen and cost less than other bits.
Long bits are handy for drilling extra deep holes or in hard to reach places. Lack of flutes means deep holes can fill with chaff.
Making holes in studs, joists, and walls to run cables. Any other time you need a quick hole in the wood and don’t care how it looks.
These are similar to twist bits, but they have a large single flute to remove chips and a screw tip to help get it started and stay centered. They are made for wood and other soft materials, they can be readily sharpened, and are usually long.
But unlike spade bits, they leave neater holes and require much less torque to turn. In fact, they turn so easily they were the first choice back when hand powered drills were popular.
CONS: Limited to soft materials and holes 1/4 to 1-1/2 in diameter. Forster bits are flat-bottomed with a point in the center to keep it on target.
They tend to be expensive but provide high precision and finest finish of any best drill bits. Because of the way they work they cut holes with extremely smooth sides and flat bottoms, which makes them attractive for many woodworking projects.
They tend to be expensive, but a single bit can cut many sized holes. They’re typically labeled by the minimum and maximum size of holes they can cut, and the increment between the steps.
The size of the hole is typically inside the flute at each step. The straight flute prevents the bit from deforming the metal as it cuts through.
(The spiral flutes on twist bits often grab and pucker sheet steels when cutting larger holes.) They’re accurate and quick, allowing you to drill many size holes without changing a bit, and by lowering the bit to touch the beginning of the next step you can easily produce a perfectly debarred (smooth-edged) hole.
USE FOR: Cutting neat holes in thin sheet material, like control panels, project cases, and linoleum. These are literally a saw blade bent into a circle, with a twist bit in the middle to help keep it centered.
Since they’re not removing as much material they don’t need as much pressure as a Forster bit the same size. This lets different sized hole saws to be affordably swapped out and dull ones replaced.
PROS: Can cut large precise circles with minimal effort. Like most specialty tools they’re really only good for their stated purpose, so don’t try to use a concrete bit for acrylic (or vice versa).
For drilling wood and metal the above choices will work well, but don’t be afraid of a specialty bit if you’re faced with difficult material. I noticed that quite a few people have a common concern that drilling holes in joists will make them weaker.
I’m here to let you know that you can safely drill holes in joists by following a few simple guidelines. Two common types of joists are used in the construction of residential homes.
In order to keep the integrity of the joists, you will need to follow some rules when drilling through them. These joists are quite easy to drill holes in, as long as you stick to the guidelines below.
Size: The diameter of the holes cannot exceed a third of the joist depth. Position: The holes must be at least 2 inches (50 mm) away from the top or bottom edge of the joist.
Size: Keep holes in these joists to a maximum of 1.5 inches in diameter (38 mm). The flanges are the thicker ends at the top and bottom of the joist.
If you intend to drill any holes larger than 4 inches (100 mm) in diameter, please first check with the joist supplier/manufacturer. Once you have followed the steps in this article, then you can relax because the job would be done, and you would not need to worry about messing up the strength and integrity of your joists.
Drill holes with a diameter of no more than one-third the depth of the joist, staying 2 in. Holes anywhere in the web area of engineered I- joists, except within 6 in.
Where and how to drill joists for electrical cables or plumbing runs depends on what type of floor framing you have. From the top and the bottom if it’s a dimensional lumber joist.
The hole cannot be larger than one-third the depth of the joist, so the maximum hole size for a 2×12 joist (actual size 1-1/2 x 11-1/4 in.) You can drill the holes anywhere along the length of the joist (first photo).
If you have manufactured I- joists, you can drill holes up to 1-1/2 in. For holes larger than 4 in., consult the lumber supplier.