Reversed Plumbing Threads: What Is That And Why Do You Need That?

A regular bold and a reverse-thread bolt are basically the same thing – they are both bolts for starters. The difference being that a reverse bold, sometimes referred to as a left-hand bolt or a counter-thread bolt, the threads are wrapped around the opposite direction.

What does that mean? It means that in order to get it to tighten up whatever it is your tightening, they must be turned counter-clockwise direction. A standard bolt is turned clockwise. So, the old saying of righty-tighty, lefty-loosey would be opposite for a reversed threaded bolt. Which, while they aren’t as common in day-to-day situations, they are fairly common in the plumbing industry.

The Basics of Bolts – Regular Thread and Reversed Plumbing Thread

The threads on all bolts have a helix. This is how they spiral on the cylinder that is the beginning of a bolt. The helix, when the bolt is being tightened, could turn in two different directions: Clockwise or counter-clockwise. This is referred to as handedness, which right-handed is how most bolts are spiraled, meaning they turn clockwise as they are screwed in.

You can see how the threads of this type of bolt have an upward angle appearance that is going to the right, which is referred to as the pitch. With a reverse pluming thread bolt, the thread is left-handed and must be turned counter-clockwise to tightened it. The angle of these threads have the appearance of going up to the left.

When Is A Reversed Plumbing Thread Needed?

Reversed plumbing thread bolts are used when using a right-handed bolt isn’t practical. Such as when your installing some type of hardware that could cause a standard thread to come unscrewed, like on a bike pedal. Reversed plumbing threaded bolts are also used in machinery such as circular saws.

In the automotive industry, reverse plumbing bolts are used on the left-hand side of vehicles in order to prevent loosening from wheel motion torque. Welding equipment utilizes this type of bolt thread for safety reason on gas-supply valves, so the user can tell the difference between the gas and the oxygen supply.

In the heating and plumbing industries, it is common to have both left-handed and right-handed couplings. This is to prevent them from working loose and leaks begin while using them.

Different Bolt Types With Reverse Plumbing Threads

There are special uses for bolts in all industries, plumbing is no different. With that being said, there are three bolt types that are common with those industries, each having their own head shape and base tip shape. Those three shapes are carriage bolts, hex bolts, and lag bolts.

A carriage bolt head is domed and smooth with the tip being flat. They are common in the machinery industry to help a connection hold fast and true.

A hex bolt has a hexagonal head, thus the name, and a flat tip. This type of bolt is common in the construction industry and used in some machinery. Typically, a nut is paired with the bold to make the hold tighter.

Lag bolts and hex bolts look similar, but the lag bolt has a pointed tip and designed to be used with wood. A popular bolt in construction projects for connecting wooden support beams.

For additional information

Bolts are typically made of steel because it is the strongest of metals and resist corrosion. There are three different types of steel used: Galvanized, stainless, or zinc-plated. Reversed plumbing threaded bolts can be found in brass, bronze, chrome-plated or nickel-plated, which are used for the cosmetic and decorative parts of plumbing.