How its done

How It's Done

The industrial revolution created a need for bolting and fastening equipment together that would resist vibration and other damaging effects. Engineers began using metal STUDS because they could be torqued to certain specifications and they were highly resistant to vibration after torquing. The problem was how to install and remove these studs with no heads.

Bolting has infinite variables and configurations: metallurgy, environment, corrosion, tensile strength, alloys, coatings, design standards, etc. Engineers design very specific standards for torquing studs but they don’t offer any specifications for stud removal.

Traditional Methods of Removing Studs

Pipe Wrenches: One of the most common methods of gripping and rotating any industrial object is a pipe wrench. Known for how they lock onto objects and combined with how inexpensive pipe wrenches are, these tools are found in every industrial shop. The problem they create is side loading. Pipe wrenches make stud removal harder, not easier, because of the mechanical bind they create at the bottom of the stud threads. Pipe wrenches are commonly used with breaker bars for horizontal leverage.

Double Nutting: this involves the process of putting two nuts on a stud and locking them together so that a wrench can be put on the nuts for rotation. Tightening two nuts against each other stretches the threads and this allows the nuts to lock in place so that the bottom nut will not move. When a wrench is used on the bottom nut, the stud will rotate with the nut. This process is time consuming and creates a phenomenon called: Side Loading

Welding a nut on the stud: by welding a nut on the end of a stud a wrench can be used on the nut to extract the stud. This process is even more time-consuming and can be quite dangerous. Side loading is an issue with this method as well.

Mushrooming a nut on the stud: a nut is threaded onto a stud and the stud is then hammered so that the nut will not come off when rotated counterclockwise. Once the nut hits the damaged threads, the stud begins to rotate and is eventually removed. Also, very time consuming and dangerous as trying to put a sledgehammer exactly on top of the stud isn’t an exact science. Wielding a sledgehammer in a shop area where employees work creates multiple safety concerns.

Breaker Bars: breaker bars are long pieces of pipe that fit over a wrench to give more leverage to create rotation. Very dangerous and highly discouraged in professional environments because of the risks of injury.

Drilling out studs: drilling out a stud requires very specialized machine tools that are completely centered over the stud. A tap hole is started and then a process of slowly increasing the size of the drill bit is done until the integrity of the stud is eliminated. The O.D. of the stud is rotated out of the housing to preserve the threads in the housing. There are many complications. 1. The specialized machine tool. 2. The centering of the drill bit directly over the center of the stud. 3. The time needed to drill out the stud usually takes hours, not minutes. 4. The housing is destroyed many times and the hole must be filled with new metal, redrilled and tapped to accept a new stud. Drilling is absolutely the slowest, most expensive and least productive method of removing studs. Why do bolting companies use drilling if it is the least productive method? Because they can charge more for drilling as a service than they can for using an industrial tool that removes studs in seconds, like the StudPuller.

Metal Disintegration: this is a process that uses controlled electrical arcs to erode the material while a coolant flushes away the eroded material. Much faster than drilling but very slow compared to rotation. The advantage of metal disintegration is that it does not damage the housing. The disadvantages are clear. It is very slow. It requires a very specific machine that can be hard to fit into tight spaces and it can be very costly.

Issues With Stud Removal and Stud Extraction

Stud Galling: Stud galling happens when the surface area between the stud and the housing become seized because of friction or pressure causing a mechanical bind. Galling can also be occur when studs in the bottom of the housing have mushroomed for various reasons usually related to friction and a buildup of pressure.

Mechanical Bind: A mechanical bind between the threads and the housing can happen for many reasons. If studs are installed using an interference fit, the threads will bind together and become frozen. Surprisingly, an interference fit is actually intentional in some cases in order to guarantee the studs will not vibrate out of the housing.

Corrosion: When studs are used to assemble equipment being placed outside, studs can corrode and rust. Generally, the threads will become brittle and erode under any torque. When equipment is placed in service in or near the ocean, the salt spray can quickly corrode the studs making them difficult to remove. Certain chemicals also corrode studs causing the studs to disintegrate in some cases.

The Science behind the Original StudPuller

Rotation is clearly the most effective, efficient and least expensive way to remove industrial studs or bolts. The objective is to grip a stud and through the proper use of torque, start the rotation process. The truer the rotational circle, the less friction will be applied to the threads of the stud and the housing. This is one of the reasons impact wrenches are used. There is no side loading with impact wrenches. Sometimes, hydraulic wrenches are also used. Impact wrenches also utilizeharmonics in breaking the bind between the threads. The hammering effect of the impact wrenches vibrates the stud and creates these harmonics, which assist in removal. The StudPuller is designed with two opposing jaws that ride on two opposing cams. These camsare placed into the tool as two eccentric circles

Comparison Chart

TRW Industries

Select a Method:

Safety:

Safer; Reduces Risk of Injury

Operator injury could occur when over tightening or shearing a stud.

Possible burn or ignition of other materials

Flying debris & metal shavings

Back injuries

Low risk if set up properly

Science:

The StudPuller uses two opposing jaws on internal cams to grip and squeeze studs to
create rotation of the stud.

Binding two nuts against each other creates a mechanical bind, which stretches the threads

Damages stud and possibly the housing

Drilling a stud is a slow, heat-building process that grinds away metal with risk of slipping off-center and damaging threads.

Side loading occurs when “pulling” on a stud. This creates a mechanical bind in the threads

An alternative to drilling, MD uses an electric arc to break down the metal and burn through the center until the stud collapses. this method usually guarantees the protection of the housing over drilling. The cutting action of a metal disintegrator is accomplished by creating a series of intermittent electric arcs that break down the hardest metals into minute particles.

Common Issues:

Rotation is the fastest, safest and least expensive way to remove studs. issues are lack of training, burning jaws, under powered equipment, lack of proper air supply.

Nuts just rotate and don’t lock against each other, nuts won’t release after extraction, stretches threads, uses lots of time

Having a welder on hand, nut doesn’t weld on center, weld breaks, stud destroyed

Inordinate amount of time, getting drill into tight spaces, set up time just to get started, possible damage to housings

Safety issues: pulling on a breaker bar is extremely dangerous and bad for the back, heavy side loading, damaging the housings and threads, bending studs or shearing studs

Set up time is high, arc time is based on diameter of stud and constant monitoring, machines are large and don’t fit in tight spaces, machines are expensive and usually come with an operator

Productivity:

Fastest; Increases Productivity

Slow

Slow time to weld and cool

Slow time spent doing set up and drilling

Very slow

Materials Used:

StudPuller

2 Nuts

1 Nut

Machine tools or drill press

Pipe wrench and breaker bar

Spark Erosion Machine