Monday, December 11, 2023

What are pipe threaders and how to choose them?

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For any application in which it is necessary to machine threads on a surface, we have at our disposal various methodologies and tools.

For example, if what we have to do is the occasional machining of a few threads, there are a number of hand tools that lend themselves efficiently to the job, such as taps (for threads outside) and taps (for threads interiors). Another useful hand tool is the ratchet that we see in the figure below, which allows the external threading of pipes in the American type (NPT) and “gas” type (BSPT and BSPP).

Threading cart

On the other hand, if we have machines, such as a lathe or a milling machine, we can carve threads outdoors with greater ease and comfort.

However, when it comes to getting large series of threads, for example, in screws, thin and long bars, or blind or through holes in square plates, all these devices become impractical and it is on that occasion when the application of the threading machines it becomes essential.

And if we talk specifically about pipe threading, normal operation in domestic, commercial and industrial applications of plumbing, electrical, heating, ventilation and air conditioning (HVAC) systems, supply of gases or fluids under pressure, etc., then the pipe threading machines they become a necessity.

What is a pipe threader and how does it work?

Basically, the threaders tubes are electric machines activated by a motor, which fulfills the function of centering and holding a tube in a chuck unit for the purpose of turning that tube to perform not only an operation of threaded, but also, if the machine allows it, cut Y reamed.

The pipe threader cutting tool is a series of threading combs, a name that should not be confused with the screw comb, a gauge or caliper used to measure the pitch of thread of a screw. In another article, we mention more details about these combs and how to select them according to the need in terms of what is involved in measuring and identifying them according to diameter.

The threading combs they are mounted on a head or die in a radial or tangential order, following location guides according to the diameter of the tube. To ensure perfect machining and a long life of the thread obtained, the system must be continuously lubricated during the machining operation. threaded, so the manufacturer also usually supplies the recommended oil for this purpose.

Within the specific group of pipe threading machines We can choose between two different models, according to our needs.

a) Stationary threading machines

They allow cutting, reaming and threading pipes in different diameters (between ¼ inch and 4 inches) and in a variety of materials, such as steel, stainless steel, cast iron, lead, brass, copper, PVC, HDPE, etc. This means that these teams can:

  1. Divide the tubes into two or more sections according to the length marked for the proposed need (cut).
  2. Enlarge or round the hole in the tube diameter and remove burrs (reaming).
  3. Generate a thread in the tube to be able to couple it (threaded).

In the following figure we see a typical model of pipe threader stationary or bench.

Figure 2 - Threading Machine

Figure 2 – Threading Machine

In these two videos we will learn how the threaders and how to use them correctly, both for pipe preparation and for threading. It should be noted that, generally, this type of machine is provided with a induction motor, which has the characteristics that we will see next.

b) Portable threading machines

With a compact and practical design, similar in appearance to an angle grinder, these machines They operate freely in hard-to-reach places, making them ideal for service and repair in industrial environments. They are used only for pipe threading and can accommodate diameters up to 2 inches. The figure below shows a typical example of a portable pipe threader.

Figure 3 - Portable Threading Machines

Figure 3 – Portable Threading Machines

The video that follows shows the step by step in the use of a portable threading machine, that can carve threads both left and right, and at slow or fast speed. These machines have a universal engine, suitable to ensure portability and easy handling at low cost.

How to choose a pipe threader

Each model of threader it presents its particularities and responds to different selection criteria, determined not only by the needs, but also by the type of motor that they include.

Since this decision is important, we are now going to make, as a guide, a series of considerations that we must take into account to acquire or rent a pipe threader with their corresponding combs.

a) Considerations on threading dies

The threading combs They are prisms, one of whose faces has machined grooves that are equidistant from each other and that exactly reproduce the profile of the thread fillet to be cut. Once tempered, they are ground and sharpened for cutting.

According to their work disposition in the head or thread, the combs can be radials or tangential, and have a slightly conical area to facilitate the entry and self-centering of the part to be threaded.

The material with which the combs are made can be alloy, high speed steel (HSS) Y HSS for stainless steel. All three types are capable of carving quality threads, but, as we can infer beforehand, alloy combs are the most economical. HSS ones last longer than alloy ones because they withstand high temperatures without losing hardness, allowing them to cut faster than alloy ones at room temperature. As its name implies, HSS stainless steel dies are specially designed for cutting threads on stainless steel tubes, a material with a wide application, even in very particular environments. When it comes to choosing the material, it is clear that, despite their higher cost, HSS combs offer a much higher durability and versatility that, ultimately, will pay off the extra expense.

The threading combs They are usually sold in four piece sets covering the most common thread types ie NPT, Metric and BSPT. The following figures show the profile of each comb and the types of threads they carve.

NPT threading machine

NPT threading machine

Metric Thread

Metric Thread

BSPT thread

BSPT thread

b) Universal and induction motor considerations

As users of power tools, we probably don’t think much about the two main types of motors used to power them. However, the differences in performance and price deserve our attention.

As in all considerations relating to the electric tools, our decision must be based on projected use. If you are new to the art of machine threading or doing jobs on site, a universal motor may be the smartest choice.

If we are specialized dealers in threading machines, it is quite possible that all our models have induction motors, equipment that will also be extremely useful if, on the other hand, we work in a workshop where the threaded of tubes is a daily task.

Therefore, in the following table we will highlight some differences between universal motors and of induction that do not point to “one engine is better in all situations”, but to facilitate our decision.

Difference Between Universal Motors and Induction Motors

Difference Between Universal Motors and Induction Motors

How do we base our decision on these characteristics?

Ultimately, if we look for a threader in which we can choose between models with induction motor Y universal engine, we must ask ourselves how often we will use the tool.

If what we are looking for is a portable threading machine, the universal motor will be the best choice. But if what we need are stationary machines, where the difference in weight between both motors is negligible (because they are only a small fraction of the total weight of the machine), induction motors will be the suitable industrial alternative.

The threaders with induction motor involve a higher initial outlay of money, but will have a higher resale value when we get rid of them. Instead, the threaders with a universal motor they will be cheaper to buy, but their resale value will be lower.

All this means that if we are about to acquire a pipe threader (or any other power tool for that matter) with a basic understanding of the two main types of motors that power them and with a definite idea of ​​our work projects, we will certainly be in a position to make the right choice.

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