The Only Guide To A Drill Rod You’ll Ever Need

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A drill rod is a common term in the machinery and manufacturing industries. You can use drill rods to manufacture various tools such as cutters, hot-work tools, machine parts, punches, files, and more. But, do we know how to choose the right drill rod for our needs?
Drill rods differentiate in regards to toughness, durability, temperature resistance, and applications. With so many different material grades and types to choose from, how do we ensure we choose the correct drill rod?
That’s where we come in – this is the only guide you’ll ever need to drill rods, their uses, and applications. This guide is suitable for complete beginners as well as professionals in the industry.
Let’s see some of the most frequently asked questions on the subject of drill rods!
What Is a Drill Rod?
Simply put, a drill rod is a lengthier steel piece of easy-to-mold tool steel that you can use for machining to produce different tools and parts.
Typically, drill rods are round. However, there are some square ones, such as the square kellys you’ll see below. Drill rods are generally soft enough to be machined into their final form.
Drill rods need to have a clean and smooth surface. To manufacture them in this way, we usually use precision grinding.
What Is a Drill Rod Used For?
Drill rods have many different applications. Producers usually use drill rods for manufacturing drilling bits, shafts, dowel pins, reamers, punches, taps, hammers, files, cutting tools, hot-work tools, etc.
Different grades of drill rods are best suited for specific uses. For example:
W1 is suitable for cold-work tools, hand-held tools, cutting tools, punches, dies, etc.;
O1 grade is best for punches, dies, and gages;
A2 and D2 can be suitable for hobs, rolls, knurls, coining dies, punches, dies, etc.;
S7 gade is perfect for knock-out pins, drift pins, stamps, grippers, track tools, river sets, mandrels, circular pipe cutters, and more;
H13 (or V44) is suitable for hot-work tools, plastic molds, die-casting tools, core pins, ejector pins, and more;
Types of Drill Rods According to the Manufacturing Process
According to the manufacturing process they go through, there are three different types of drill rods: air-hardening, water-hardening, and oil-hardening. Each of these drill rods has various uses and applications. Let’s explain something about each of these different types of manufacturing processes and drill rods & casing.
Air-Hardening
We’re starting from the toughest category of tool steel – the air-hardened drill rod. Air-hardened steel has more alloy, and this is what makes it so hard and resistant. After heat treatment, you can leave air-hardening types of drill rods to harden in still air.
Air-hardening drill rods have superior machinability and wear resistance when compared to oil or water-hardening rods. Furthermore, air-hardening is safer than water or oil-hardening in regards to distortion and dimensional stability.
Oil-Hardening
Oil-hardening drill rods are second in line when it comes to their hardness and durability. Although oil-hardening rods have less alloy than air-hardening rods, they’re still rich enough to withstand welding. On top of that, oil-hardening steel is suitable for machining.
If you’re not sure what the term “oil-hardening” means, it implies heating the rod until it’s glowing red and then dipping it into a pool of warm oil. With this, the steel becomes hard and ready for machining or welding.
Water-Hardening
And finally, we have the water-hardening drill rods, which portray the lowest alloy content but are excellent for machining. However, they’re deficient in alloy content, which signifies that they’re not structurally suitable for welding purposes.
To harden a drill rod with water, we first heat the steel until it becomes glowing red, and then we plunge it into a pool of water to cool off. Once the metal is hard, it can be easily machined but not welded. You can usually use water-hardening drill rods for the manufacturing of files or hammers.
Types of Drill Rods According to Different Threads
We can classify drill rods into three different types according to different threads: ordinary drilling rigs, square kelly rods, and heavy-weight drill pipes.
The Ordinary Drill Rod
We can easily recognize the ordinary drill rod since it’s the central or basic part of the drill stem. At the top, the ordinary drill rod connects to the square kelly (explained below), and at the bottom, it’s attached to the drill collar.
In borehole digging, the function of the ordinary drill rod is to deepen the hole, transmit torque, and move the drill up and down.
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