Anatomy of Coil Tattoo Machines

Between 30-35% of Americans have at least one tattoo, statistics say. Most people can think of numerous friends, family or celebrities with tattoos. The trend is on the rise and giving way to growth in the tattoo industry as a whole. Tattoos have become a cultural norm in many ways. Most people select an artist, bring their design, and let the artist work their magic. The buzz of a tattoo machine can be therapeutic to some – but have you ever wondered what they’re made of?

Coil Machines

Coil tattoo machines function through electromagnetism. They feature coils made from a conductive cylindrical center post that are then wound with an insulated copper wire. The coils are not active until attached to a power supply. Tattoo machines can feature one, two, three or more coils – with two being the most common. This type of machine was patented in 1891 by Tom Riley. While his invention was a single coil device made of an electromagnetic doorbell, it paved the way for modern machines.

Coils

Most coils on the market have a general composition. The cylindrical center post is made of conductive material and features a top and bottom that protrude slightly from the center, similar to a spool. Even more like a spool, each post is wound with an insulated copper wire. The wire is threaded through one of two entry points at the base of the post. Carefully and purposefully the wire is then wound up and down the post, in the same direction, to achieve a certain number of wraps. Wraps are the number of layers of wire – standard machines can have anywhere from 6-12 wraps. The amount of wraps determines how much force the machine has, as the electromagnetic coils will be stronger with more wraps. The wire is then threaded through the other entry point. With the wire threaded, these entry points act as a positive and negative lead.

Binding Posts

Binding posts are electrical contact points fixed to the frame of the tattoo machine that hold capacitor leads in place to power the machine. Traditionally, there are two binding posts – a front binding post and a rear binding post. The positive lead is fastened to the rear binding post, and the negative to the front binding post. A clip cord is attached to the rear post and the armature bar to deliver electricity from a power supply.

Capacitors

A capacitor is a small tube-like component that connects to the positive and negative coil leads. It acts as a regulator for the amount of power circulating in the coils, which moves the armature bar. Capacitors come in a few different sizes, the size or volume determines how quickly the power is exchanged to the coils and thus how fast the armature bar moves.

 Why does size matter? 

Capacitors act as storage for electrical charges, and send them to the machine as needed. The size or volume is measured in units of Farad or uF. Smaller capacitors have less volume so they hold and exchange chargers quickly, which allows the machine to run faster. Respectively, larger capacitors have more volume so they store and send charges at a more gradually rate – which allows the machine to run a bit slower. Smaller capacitors are great for liners, while larger ones are great for shaders or color packing.

Armature Bar

The armature bar is responsible for moving the needle, it is made of magnetically responsive metal. It is fixed on the machine frame by a rear spring that allows the bar to move up and down. At the front of the bar is the front spring. The electromagnetic force of the coils pulls the armature bar down, opening the circuit when contact is made. The electromagnetic field then dissipates, causing the armature bar to leap back upward causing the front spring to make contact with the conact screw. This process repeats over and over, creating that familiar buzz and moving the needle in and out of the skin.

 Front Spring & Rear Spring

The front and rear spring are typically made of spring steel. Spring steel has a different composition that normal steel that allows it to return to its original shape after being bent or twisted. The rear spring is fastened to the machine frame by a secure mounting screw and attached to the armature bar. The rear spring controls the downward force of the machine – a thinner spring means that the machine moves with less force, where a thicker gauge spring runs with greater force. The front spring is fixed to the bar at the same point as the rear spring but is not fastened to the frame. This is so the bar can move. The front spring is bent at an upward angle in order to touch the contact screw. Silicone grommets or O-rings in different widths are used to adjust the angle of the front spring.

 Contact Screw & Components

As mentioned before, the binding posts act as electrical connections. The front binding post is connected to the negative lead and also holds the contact screw. When the armature bar is released from the coils’ electromagnetic field, the front spring leaps upward to touch the contact screw and complete the circuit. The lenth of the contact screw can be adjusted to control how far the armature bar has to travel upwards.

 Needle Assembly

The tattoo needle is attached to the end of the armature bar that faces the front of the machine. It is secured to the bar by a rubber or silicone grommet. The needle runs through a tube which is secured at the bottom of the frame by the tube vice. Tube vices are traditionally quite simple, usually a screw that is adjusted to the width of the tube to hold it in place. The tube allows the needle to move in a controlled space, rather than all over the place. Tubes typically feature textured grips that make the machine easier for the artist to hold more comfortably and securely.

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