Tattooing machines require certain sized spacers to be inserted depending on the type of tattoo you wish to create. Fine line tattoo spacers are different than shading spacers. Many tattoo artists who tattoo often prefer to have more than one tattoo machine set in a certain configuration for only one purpose to save time and so that they know exactly what to expect from the configuration. Coins are commonly used as their thickness accurately sets the machine up for a specific setting. Welding a coin onto the machine's tension screw is a good way of permanently setting it to such a setting, whether it be for shading or lining.
Remove the contact screw from the rear of the tattoo machine.
Clean the tip of this screw with some steel wool, as well as both sides of the desired coin. Due to their thickness, nickels are best suited for shading; dimes are best suited for lining.
Place the coin flat on a metal workbench. With the tip of the contact screw in the centre of the coin, hold the screw in place with the pliers in an upright position.
Heat both the screw and the coin using the torch. Once they are both beginning to turn red hot, touch the brass brazing rod to where the screw meets the coin.
Coat the circumference of the tip of the screw where it meets the coin with brass, lightly touching the rod to the junction of the screw and coin, then allow the two to cool.
Replace the contact screw into the tattoo machine so that the coin now touches the front spring. Do so by removing the front binding post screw so that you can load the contact screw with the coin welded to the tip.
Do not touch the coin or screw with your hands until they have been sufficiently cooled. Always wear eye and hand protection while welding.