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Powder Actuated Tools

Chapter A3 – Uses Powder-Actuated Tools

Prerequisite Knowledge:

– Experience operating PATs
– Familiarity applying PATs on a job site

Topic 1 – Operate and Maintain Powder Actuated Tools

The PAT (Powder Actuated Tool)

The PAT consists of three primary components: the tool, the fasteners, and the power load (cartridge). All of these components are determined based on what material is being fastened into such as structural steel or concrete.

There are two categories that PATs fall under: High Velocity Tools and Low velocity tools.

High velocity tools are much less common as low velocity PATs. They are categorized by firing fasteners at velocities of 150 m/s or greater by use of expanding gasses produced by firing powder. Because they are capable of producing such high velocities, there is a danger of the fasteners ricocheting and causing injury to the operator and workers nearby. With the development of low velocity tools, the high velocity PAT is no longer produced.

Unlike the high velocity tool, the low velocity tool fires the fastener by use of a piston which is driven by (much like the high velocity tool) the rapid expansion of gasses produced by the burning of powder. While low velocity tools are much safer, they required more knowledge and maintenance to operate as the piston is often required to be changed depending on the type of fastener being driven.

Power Loads

Filled with gunpowder, the power load is a blank cartridge that powers PATs. The power load must be properly chosen depending on the type of material that is being fastened into (the base material). The load is contained within the cartridge by two means: wadded ends and crimped ends. The wadded ends are used strictly with high velocity tools. Crimped ends are much more common and can be used by both categories of PATs.

As the power loads contain gunpowder, a number of safety precautions should be taken:

– Use the load recommended by the manufacturer
– When using an unfamiliar tool, start with a lower load and work up in power until proper penetration is achieved
– Do not carry power loads in pockets or aprons. They should be stored in proper containers.

Fasteners

Fasteners for PATs come in three basic designs:

– Nails, which are used to directly fasten an object to either concrete or steel
– Threaded studs, which are used to bolt objects
– Eyelets, which are used to anchor support wires such as for suspended ceilings

It is essential that the fastener chosen is compatible with the tool being used. Always follow the manufacturers recommendations when choosing a fastener. Because the fastener is driven into very hard material, they must be hardened enough to penetrate steel without deforming and be able to withstand the working load imposed on it after fastening.

Fastening Into Concrete

Only concrete which has sufficiently hardened is able to be fastened into. The mix design and weather conditions can have a large effect of when sufficient hardening has taken place. Typically, concrete should be allowed to set for 3-5 days before attempting to fasten into it. The fastener obtains its holding power by wedging itself between the material and compressing the concrete around it which then grabs onto the fastener after it has been driven.

Fastening into Steel

When fastening into steel, the holding power is achieved by friction between the steel and fastener. The friction is a result of the penetration of the fastener into the steel which produces a compressive force around the fastener. The holding power is determined by the diameter of the pin and the thickness of the steel. Often the shank of the fastener is knurled to provide greater holding power. When the fastener is driven, it heats and hardens the steel, and no structural strength is lost.

Using A PAT

There are three factors to consider when using a PAT:

– Suitability of base material
– Location of the fastener
– Safety regulations

Suitability of Base Material

The suitability of the base material must be determined prior to using a PAT. While some materials may be too hard to safety drive into, there are many materials that are too brittle and will shatter when being driven into such as tile, brick, or glass. A good test is to hit a pin with hammer into the base material. If the surface chips or cracks under this test, it is too brittle. If the fastener is easily driven in with a hammer, the material is too soft. As a general rule, cast iron, spring steel, and welds are too hard to drive into. If the fastener tip dulls and does not leave an indentation when hit with a hammer, the base material is considered too hard to safety fasten into.

Location of the Fastener

When choosing the location of fasteners, there are two primary considerations:

– Distance from the edge of material; if the fastener is placed too close to an edge (within 3”) of concrete, it is likely that the piece will break off and the fastener will fail. In steel, it is recommended that the fastener be no less than ½” away from the edge and 2” away from welds
– Spacing; because fasteners rely on compressive forces within concrete, it is recommended to place fasteners at least 3-5” apart as the compressive forces may cause a large chunk between them to break out if they are placed too close together. In steel, fasteners should be placed no less than 2” apart.

Another consideration is penetration and the thickness of the base material. Generally, when fastening into concrete, the base material should be at least 3x as thick as the penetration of the fastener. When fastening to steel, the fastener should fully penetrate the base material. Typically, the fastener should protrude ¼” through to prevent the fastener from backing out over time.

Safety Considerations

– Always wear hearing and eye/face protection when using PATs
– Use a lower charge and work up to the proper load
– Always perform a hammer test on the base material
– Ensure the barrel is empty when placing a fastener in the barrel
– Observe proper spacing and placement of fasteners
– Keep the tool in good maintenance. Daily inspections should be performed, with the tool cleaned and lubricated
– Do not load the tool until it is ready to be used
– Store power loads in a dry, secure location
– Do not use PATs near flammable or explosive gasses.

Review Questions

  1. Name the three components of a PAT system.
  2. What factors effect the holding power of a fastener in concrete?
  3. Where are knurled shanks used?
  4. What PPE should be worn when using a PAT.
  5. What type of maintenance should be performed daily on a PAT?

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Carpentry Refresher Program Manual Copyright © by Saskatchewan Indian Institute of Technologies-Trades and Industrial is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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