What Drag Bit Do I Need? Chevron Vs. Step
Drag bits are used for drilling across a wide variety of industries – from mining, water well, and geothermal drilling to natural gas and oilfield drilling. Because they are used in various environments and applications, drag bits are some of the most popular bits used worldwide.
There are different varieties of drag bits, but the most common are chevron drag bits and step drag bits. Depending on your formation type and density, the ideal size of the bit and style may vary. If you’re questioning, “What type of drag bit do I need?” you are in the right place. We’ve outlined chevron bits vs. step bits here, but you can always ask the experts at O-K Bit, too!
O-K Bit is a leader in providing new and refurbished bits for any type of drilling in nearly any formation. Contact O-K Bit today, and our team of knowledgeable experts can supply the products and information you need. We’re always happy to guide customers to the best bit for their specific drilling project.
When should I use a drag bit?
A drag bit is probably your best bet if you are attempting to drill through soft formations like clay, sand, and some very soft rocks. They are designed to work well in soft formations, but if you are drilling in harder or more rocky formations, you might need to explore tricone, PDC, or another bit type.
Drag bits are often used to drill pilot holes. If you are looking to sample and log a series of cuttings, a drag bit would be helpful to complete this work. Because of the design and cost of drag bits, they can also be more economical for drilling.
How does a drag bit work?
Drag bits, including chevron bits and step bits, are most often made of alloy steel, but they can be manufactured using tungsten carbide. Some are solid cast, and others are welded. The construction of tungsten carbide bits makes them more durable. Tungsten carbide bits may serve you better if drilling in a rocky formation or for other specialty purposes. If you’re drilling in sand or clay, an alloy steel bit will probably suffice. The cutting structures vary on chevron drag bits and step drag bits. Still, both designs feature a central opening with radial cutting structures or wings.
To understand how drag bits work, imagine you’re drilling a small pilot hole in a wall with a tiny household drill bit. After it’s drilled, that pilot hole can then be used as a guide for a larger bit to bore through. Drag bits work in the same way; the tip of the bit essentially creates a pilot hole for the rest of the cutting structure to shear and expand the hole. Drag bits do not have the fastest rotation or rate of penetration (ROP), but they are effective and can be very precise.
Another benefit of drag bits is the simplicity of design and lack of rotating parts. While roller bits or others may become stuck in soft formations, drag bits often drill more efficiently and require less maintenance.
Step Drag Bits
Step drag bits are one common type of drag bit and one of the most common bit types used worldwide. As the name indicates, the cutting structures of these bits feature a stair-stepped design. They are pointed at the top, stairstep down, and become wider at the base of the bit. Step-type drag bits can have three or four wings. Four-wing bits are typically more durable and longer lasting. You’ll also find them more precise and able to drill a straighter hole. Three-wing step drag bits tend to drill faster but with less precision. The number of steps usually depends on the size of the bit.
Uses for Step Drag Bits
- Drilling in sand, clay, shale, limestone, and some gravel
- Sampling and logging cuttings – because the design provides larger cuttings
- Drilling efficiently – step drag bits can maintain rotary table speeds of 60 to 80 rpm
- Drilling for water wells, mining, geothermal, environmental, and exploration drilling
Chevron Drag Bits
Chevron drag bits are the other typical style of drag bits. Three or four wings create the cutting structure of chevron bits in a radial formation. Each wing is pointed at the tip and widens towards the base. Each wing forms its own chevron shape, as the name indicates. Like step drag bits, chevron bits can have three or four wings. The tips of the wings are often made of tungsten carbide or another highly-durable material to strengthen the bit and attack difficult rock formations.
Generally, chevron bits are more durable than step drag bits and can successfully drill in more rocky and abrasive formations. Another feature of the chevron bit is its ability to drill through plugs and concrete casings. If you get stuck in a jam, the chevron bit can probably bail you out – it really is a robust and vigorous bit that can be used almost anywhere. You’ll find using a chevron bit requires more pressure on the bit, and the drilling process may be a little slower than a step bit.
Uses of Chevron Drag Bits
- Drilling in both soft and medium formations, including shale, sandstone, limestone, other rock formations, casings, and concrete
- Drilling slowly in harder formations and maintaining a consistent borehole – 50 to 60 rpm is typical
- Drilling for water wells, mining, geothermal, environmental, and exploration drilling
So, What Kind of Drag Bit Do I Need?
Without understanding the geology and environment in which you are drilling, it’s hard to say exactly which type of drag bit you need. There are a few things you can consider to help determine which drag bit is best, though. Is your rock formation soft and porous (step bits), or is it a medium to hard formation (chevron bits)? Do you prefer to cut through the rock very quickly (step bits), or slowly and steadily (chevron bits)? Do you need to collect cutting samples to log (step bits)?
After learning more about step drag bits and chevron drag bits, the answer may be pretty clear-cut. If it’s not, that’s okay. Choosing the right bit can make all the difference to the cost, efficiency, and success of your drilling project. We understand you want to make the right decision. O-K Bit is ready to help. Our team is the world’s largest retailer of refurbished bits in the world, and we really do know our stuff. Contact us today to get started.
