What Is Needle Stroke in Permanent Makeup and Tattooing? Myths, Physics, and the Real Principles Behind Machine Performance
What Is Needle Stroke?
Why Are There So Many Myths Surrounding Needle Stroke?
Why Does Changing the Needle Stroke Alter the Artist's Perception?
Editor's Note
What is needle stroke? It is one of the most widely discussed specifications of permanent makeup and tattoo machines. Nearly every manufacturer lists it among the key technical parameters, educators explain the differences between short and long strokes, and artists frequently debate which option is best suited for lips, eyebrows, or eyeliner procedures.
However, ask one simple question—what exactly changes when the stroke length is altered?—and there is no single answer.
Some believe that a shorter stroke allows the needle to make more punctures per second. Others argue that the operating frequency remains virtually unchanged, and that the only real difference lies in the impact force. These two viewpoints have coexisted within the professional community for years, yet they are rarely supported by engineering-based explanations.
To explore this question, the editorial team at PULSE PMU turned to the people who actually design tattoo machines. We asked the same set of questions to two equipment manufacturers: Evgeniy Murzo, representing the Belarusian brand JACK & ALEXX, and Helge, representing ACUS, a European manufacturer of professional tattoo machines.
We expected to receive different answers. Instead, both experts arrived at remarkably similar conclusions independently of one another. Their agreement made it possible to examine one of the industry's most persistent myths from an engineering perspective rather than through subjective perception.
What Is Needle Stroke?
Simply put, needle stroke is the distance the needle travels between the highest and lowest points of its motion during a single operating cycle.
It is important to understand that this is not the same as the depth of needle penetration into the skin. Implantation depth depends on multiple factors, including needle protrusion, the artist's technique, skin tension, hand speed, and other variables. For this reason, three distinct concepts should not be confused:
Needle stroke is the amplitude of the mechanism's motion (generated by the eccentric), defined as the distance the needle travels from the highest point of its movement to the lowest (the motion follows a sinusoidal path).
Needle protrusion is the distance the needle extends beyond the tip of the cartridge during operation.
Implantation depth is the depth to which the needle actually penetrates the skin.
These parameters are related, but they are not the same.
Where Does Needle Stroke Come From?
In any rotary machine, the needle's range of motion is determined by the eccentric mechanism.
The motor shaft rotates in a circular motion, while the eccentric mounted on the shaft converts this rotation into the familiar reciprocating motion of the needle. The farther the center of the eccentric is offset from the center of the motor shaft, the greater the amplitude of the needle's movement and, consequently, the longer its stroke.
Replacing the eccentric allows the machine's stroke length to be changed without altering its fundamental operating principle. However, it often significantly changes the machine's overall performance characteristics and the way it feels during use.
This naturally raises an important question: if the needle has to travel a different distance, does that mean it makes a different number of punctures per second?
This question has been at the center of an ongoing debate within the industry for many years.
Why Did the "More Punctures per Second" Myth Appear?
At first glance, the theory seems perfectly logical.
Imagine two machines: one has a 2.5 mm stroke, while the other has a 4.5 mm stroke. It seems obvious that the needle with the shorter stroke travels nearly half the distance. Therefore, it should complete each cycle more quickly and make more punctures in the same amount of time.
This is exactly how many artists explain the difference between short and long stroke machines. In fact, the idea appears so intuitive that it has long been accepted almost as an unquestionable fact.
However, engineers propose looking at the process from a completely different perspective.
The fundamental flaw in this explanation is that it considers only the distance traveled by the needle while largely overlooking the role of the motor itself. Yet it is the motor that determines the frequency at which operating cycles are performed.
This single point fundamentally changes our understanding of how a modern rotary machine actually works.
What Did the ACUS Engineers Explain?
According to the engineers at ACUS, changing the needle stroke in most modern rotary machines has little to no effect on the number of operating cycles performed by the needle (measured in hertz). Modern brushless motors maintain nearly the same rotational speed even when fitted with an eccentric of a different size.
This means that increasing the stroke length does not normally cause the needle to operate more slowly. Instead, something else happens: the needle simply has to travel a greater distance in virtually the same amount of time.
As a result, the needle's travel speed increases, and with it, the energy delivered by each individual impact.
This is the key conclusion of the entire investigation.
A longer stroke has little effect on the number of punctures per second. Instead, it changes the needle's travel speed and the force of each individual impact.
This is precisely why long-stroke machines are often perceived as feeling more aggressive and more powerful.
During a procedure, an artist cannot perceive a difference of just a few hertz (where hertz refers to the number of needle cycles per unit of time). What the artist does perceive very clearly is the force of each individual impact. As a result, the machine feels as though it is operating differently, even though what actually changes—assuming the motor shaft maintains the same rotational speed—is not the needle's operating frequency, but the energy delivered during each working cycle.
What Did Evgeniy Murzo's Experience Show?
To determine whether theory aligns with real-world performance, the editorial team at PULSE PMU consulted Evgeniy Murzo, manufacturer of JACK & ALEXX equipment.
His conclusions were almost identical to those of the ACUS engineers.
According to Evgeniy, one of the most common mistakes is evaluating a machine based solely on its stroke length. In reality, a machine's performance is determined by a combination of factors, including the type of motor and its torque, the eccentric, the electronics, the overall weight, the center of gravity, and numerous other engineering characteristics. This is why two machines with the same stroke length may perform completely differently, while machines with different stroke lengths can feel remarkably similar in practice.
Another widespread misconception concerns operating voltage. Many artists compare machines based on the voltage displayed on the power supply, saying things like, "I work at 6 volts," or "The machine runs faster at 7 volts." However, this comparison is meaningful only when referring to the same machine model.
Different manufacturers use different motors and motor control systems. As a result, two machines operating at the same voltage may produce completely different operating speeds, measured as the number of needle cycles per second. From an engineering perspective, needle cycles per second are far more meaningful than the voltage displayed on the power supply.
These conclusions are also supported by practical testing. During evaluations of the Spektra Xion S, which allows the eccentric to be replaced while keeping all other parameters unchanged, changing the stroke length was found to have little to no effect on the number of operating cycles. What changed noticeably, however, were the needle's travel speed, the impact energy, and the overall feel of the machine during operation.
Thus, the practical testing confirmed the conclusions reached by the ACUS engineers: needle stroke influences the machine's performance characteristics far more than it affects the frequency of needle punctures.
Why Do Artists Choose Different Stroke Lengths?
If the number of punctures per second remains virtually unchanged, a logical question follows: why do artists use different stroke lengths for different procedures?
The answer is straightforward.
A short stroke produces a gentler needle action. Each puncture is softer, making it easier for the artist to control implantation depth while minimizing tissue trauma. For this reason, short and medium stroke lengths are commonly preferred for lips, delicate skin, and other sensitive areas. They are also the most popular choice for beginners, as they tend to be more forgiving during the learning process.
A long stroke, by contrast, delivers a faster and more forceful impact. The needle penetrates dense skin more easily, making this option well suited for techniques that require more decisive pigment implantation. However, this also increases the risk of excessive tissue trauma if implantation depth is not carefully controlled. A long stroke is less forgiving of technical errors and is therefore rarely recommended for beginners.
Ultimately, stroke length is selected not because it changes the number of punctures, but because it changes the characteristics of the machine's performance required for a particular procedure.
What Did Our Investigation Reveal?
The primary goal of this article was not to prove one theory over another, but to better understand how modern rotary machines actually operate.
The most significant finding was that two independent sources—the engineers from ACUS and JACK & ALEXX—arrived at nearly identical conclusions.
Both confirmed that stroke length has little effect on the number of needle cycles. Instead, the critical factors are the needle's travel speed, impact energy, and interaction with the skin.
Conclusion
For many years, our understanding of needle stroke has been shaped primarily by artists' practical experience. Today, equipment manufacturers are increasingly explaining the operation of their machines from an engineering perspective, offering a new way to interpret concepts that have long been taken for granted.
Our investigation suggests that one of the industry's most widespread myths deserves to be reconsidered. A longer stroke does not reduce the number of punctures, nor does a shorter stroke increase them. The fundamental difference lies in the needle's travel speed and the energy delivered by each impact.
Needle stroke remains an important machine parameter. However, it should not be selected based on whether one stroke length is "better" or "worse." Instead, the choice should be guided by the specific technique, the characteristics of the skin, and the clinical objectives of the procedure.
The better an artist understands how their machine works, the more confidently they can control the outcome of their work.
Acknowledgments
The editorial team at PULSE PMU extends its sincere gratitude to equipment developer Evgeniy Murzo and the ACUS engineering team for their professional insights and willingness to share their expertise. Their contributions have ensured that this article is grounded not only in practical experience but also in a solid engineering understanding of how modern permanent makeup and tattoo machines operate.
Editorial Note. This article is based on interviews with engineers from ACUS and JACK & ALEXX, as well as an analysis of technical documentation and practical equipment testing. The conclusions presented apply specifically to modern rotary machines equipped with brushless motors and should not be automatically generalized to all machine designs currently available on the market. The performance characteristics of individual machines may vary depending on their motor design, electronic control system, and mechanical configuration.
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Publication date: July 08, 2026
By Evgeniy Murzo (JACK & ALEXX), Helge (ACUS), Sergey Yakovlev (PULSE PMU)
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