Curved barbell

Barbell style piercing jewelry is composed of a straight bar and with a bead on each end, one or both beads unscrewable for removal and/or changing of the beads. Often one of the beads is fixed, either via epoxy or welding, so that only one bead is used to install or remove the jewelry. Barbell threads are usually right-handed.

They are named because they resemble the barbells that are used in weightlifting.

Named because the bar has smooth ends with receiving threads tapped into the end of the bar. In internally threaded jewelry, the bead has a receiving tube machined into it (this is referred to as "countersunk"), with a threaded post extending from the center, which mates with the threaded receiving tube on the bar. Being much less likely to cause damage and irritation, especially at the time of piercing, internally threaded jewelry is considered superior to externally threaded jewelry. It is usually slightly more expensive than externally threaded jewelry, due to the extra machining and labor involved.

So named because the shaft of the bar has threads at both ends to allow beads with receiving threads to be attached. Due to the potential damage or irritation to the piercing when the threads pass through when the jewelry is inserted or removed, this type of barbell has become less common, due to the popularity of the internally threaded barbell. This type of barbell is usually only used when the gauge of the bar is too small to allow it to be internally threaded, or in cheap, mass-produced body jewelry. Some higher-end manufacturers make externally threaded barbells with "step-down threading", where the threaded section has a smaller diameter than the wearable section; these are fairly uncommon and usually internally threaded barbells are used in their place. Step-down threaded jewelry ends can be inserted into the blunt end of a hollow piercing needle, allowing for less irritation during initial placement than regular external barbells or even internally threaded barbells.

Also known as a navel curve or curve, so named because of their curvature. A curved barbell is mechanically identical to a straight barbell, except for being curved. Curvature on a curved barbell can range from almost straight to circular, with some barbells actually being spiral, with the ends overlapping but separated to allow the insertion of the jewelry. A variation on this design is a J-bar, a slightly curved barbell (sometimes referred to as a bananabell or banana barbell) with a 90 degree bend near one end, used in vertical navel piercings to position the decorative end of the jewelry more appropriately. They can be either internally threaded or externally threaded.

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Wikipedia