A drill bit is what actually cuts into the rock when drilling an oil or gas well. Located at the tip of the drillstring, below the drill collar and the drill pipe, the drill bit is a rotating apparatus that usually consists of two or three cones made up of the hardest of materials (usually steel, tungsten carbide, and/or synthetic or natural diamonds) and sharp teeth that cut into the rock and sediment below.
In contrast to percussion drilling, which consists of continuously dropping a heavy weight in the wellbore to chip away at the rock, rotary drilling uses a electric hammer drill bit to grind, cut, scrape and crush the rock at the bottom of the well. The most popular choice for drilling for oil and gas, rotary drilling includes a drill bit, drill collar, drilling fluid, rotating equipment, hoisting apparatus and prime mover.
The prime mover is the power source for the drilling, while the hoisting equipment handles lifting the drill pipe to either insert it into the well or lift it out of the well. Rotating equipment is what sets the whole system in motion. Before the early 1900s, drilling equipment was spun using livestock and a wooden wheel, but now, the rotating equipment is put in motion by a rotary table, which is connected to a square-shaped hollow stem, called a Kelly. Connected to the Kelly is the drill collar, which puts pressure and weight on the drill bit to make it drill through the rock and sediment. Capping off the drillstring is the drill bit, and encompassing the drilling process is drilling fluid, which helps to provide buoyancy to the drill string, lubricate the drilling process and remove cuttings from the wellbore.
Types Of Drill Bits
There are a number of different types of drill bits. Steel Tooth Rotary Bits are the most common types of drill bits, while Insert Bits are steel tooth bit with tungsten carbide inserts. Polycrystalline Diamond Compact Bits use synthetic diamonds attached to the carbide inserts. Forty to 50 times stronger than steel bits, Diamond Bits have industrial diamonds implanted in them to drill extremely hard surfaces. Additionally, hybrids of these types of drill bits exist to tackle specific drilling challenges.
Various drilling designs are also employed for different results, including core bits, which gather formation cores for well logging; mill bits, which help to remove cuttings from the well; and fishtail bits, which enlarge the drill hole above the drill bit.
Different configurations work better on different formations; so a number of different drill bits may be inserted and used on one well. Additionally, drill bits have to be changed due to wear and tear. Drilling engineers choose the drill bits according to the type of formations encountered, whether or not directional drilling is required, for specific temperatures, and if well logging is being done.
When a drill bit, like a masonry drill bit, has to be changed, the drill pipe (typically in 30-feet increments) is hoisted out of the well, until the complete drill string has been removed from the well. Once the drill bit has been changed, the complete drill string is again lowered into the well.
Plenty of manual cutting applications call for a hand-held grinder and cutting wheel. Cutting sheet metal, sizing a piece for fabrication, cutting out a weld to refabricate it, and cutting and notching in pipeline work are just a few examples of what can be accomplished using a grinder and cutting wheel.
Resinoid-bonded cutting wheels are a popular choice to achieve these types of cuts because they offer portability and allow you to cut in many different angles and orientations. The bonding agent, in this case resinoid, holds the wheel together so it can cut effectively. The bond wears away as the abrasive grains wear and are expelled so new sharp grains are exposed.
By following a few best practices, you can extend wheel life, promote safety, and improve productivity and efficiency within the process.
The main considerations in using resin cutting wheels include the cutting application, the tool being used—such as a right-angle grinder, die grinder, or chop saw—desired cutting action with diamond saw blade, the material being cut, and space. Wheels typically provide a fast cutting action, long life, and tend to be cost-effective.
The two main types of resinoid-bonded abrasive cutting wheels are Type 1, which are flat, and Type 27, which have a raised hub. Type 1 wheels generally are used for straight-on cutting on electric or pneumatic right-angle grinders or die grinders and chop saws, among other tools. Type 27 wheels are required when there is some type of interference and the wheel needs to be raised up from the base of the grinder, but personal preference also plays a role in the decision. They are most commonly used with electric or pneumatic right-angle grinders.
Resinoid-bonded abrasive cutting wheels are available in various sizes and thicknesses. The most popular range is 2 to 16 inches in diameter, and common thicknesses are from 0.045 in. to 1⁄8 in. Thinner wheels remove less material during the cut.
Some types of wheels cut faster than others. The abrasive material used in the wheel is one influencer on cut rate and consumable life. Wheels come in several grain options, such as aluminum oxide, silicon carbide, zirconia alumina, ceramic alumina, and combinations of these materials.
While not as sharp as other grains, aluminum oxide provides toughness and good performance for cutting on steel. Silicon carbide, on the other hand, is a very sharp grain but not quite as tough, making it suitable for cutting nonferrous metals. Zirconia alumina is a self-sharpening, tough, durable grain that holds up well in a range of demanding applications. Ceramic alumina also is designed to self-sharpen as it “breaks” at predetermined points to maintain a consistent cut rate and long life.
When selecting a resinoid-bonded abrasive wheel, consider that products made with a mixture of zirconia or ceramic alumina with a harder bond typically cost more but offer durability and longer consumable life.
Make sure to refer to the manufacturer’s recommendations, product descriptions, and RPM ratings to select the proper wheel size and bonded abrasive material for your application. Matching the size and RPM rating of the tool to the size and RPM rating of the wheel is critical for safe and effective usage. Choosing the tool with the greatest amperage or amount of torque while staying within size and RPM requirements of the wheel will increase performance.
The kind of tool and the tool guard that you use also are factors that play a role in the type of wheel that can be used for an application. A larger-diameter wheel works best if you’re cutting deep into metal or need to cut a piece with a large diameter, for example, because it eliminates the need to rock the wheel back and forth during the cutting process. Look for a wheel with the diameter designed for the size and thickness of material being cut.
Thin wheels, on the other hand, tend to remove less metal du