Identify Procedures for Operating Portable Saws
Topic 7 – Identify Procedures for Operating Portable Saws
Reciprocating Saws
There are two primary types of saws which cut with a reciprocating action: the jig saw and reciprocating saw.
The jig saw is used in both finish and rough carpentry. It contains a thin blade which allows it to make tightly curved cuts. The adjustable base allows it to make angled cuts as well. The jig saw is capable of cutting through a variety of materials including wood, plastic, composite materials, and some metals (namely aluminum and steel). The correct blade must be used depending on the job (see image below).
With most jig saw blades, the cutting action takes place on the up stroke so, much like the circular saw, the finish side of material must be down when cutting. An exception to this is when cutting out the sink opening in a counter-top. As the finish is up, it is important to use a blade designed to cut on the down stroke so as to prevent severe damage due to tear-out.
Figure 2: various jig saw blades
The reciprocating saw (or “Sawzall”) is used almost exclusively for rough carpentry. It is capable of cutting through large amounts of material in one pass and is an indispensable tool when it comes to demolition and alteration work. Blades of varying lengths and set are available for virtually any material. While its primary use is in demolition, it can also be used to cut in tight corners due to its flexible blade. It has the ability to cut out material up a corner such as subfloor up to wall framing.
Circular Saw
Figure 3: a 7 1/4″ circular saw
A versatile tool, it is the most common saw you will find on a job site. With its adjustable base, it is capable of completing many different cuts including cross cuts, rip cuts, mitre, bevel, and compound mitre cuts. It can also be equipped with a fence used as guide for cutting repetitive widths. It can be purchased in a variety of sizes, which is determined by the diameter of the blade it accepts. The most common size is 7 ¼”. The circular is saw is equipped with a self-retracting guard. It is essential this is in good working order when operating.
Mitre Saw
Sometimes called the mitre box, the mitre saw is largely used for finish carpentry. It is capable of accurately and consistently producing mitre cuts which is extremely useful for baseboard, casing, and crown moulding. While the most basic of mitre saws are only capable of producing mitres up to 45-55°, some are also able to produce bevel and compound mitre cuts (known as compound mitre saws). It is incapable of completing rip cuts.
Figure 4: a 10″ compound mitre saw
Much like the circular saw, the mitre saw is sized according to its blade diameter. The most common size is 10”, however they are also available in 7 ¼” as well as 12”. Blade selection is highly dependent on application and material being cut. For the smoothest cut, choose the correct blade (ensure it is sharp) based on material being cut, and complete cuts at a proper rate. Generally, with harder materials, a slower cut is required.
As the material is stationary during cutting, it is important to observe a few rules: ensure guards are in working order, don’t attempt to cut material shorter than 12”, do not force the saw through the cut, and always wear proper apparel including safety glasses. When performing maintenance and service on a mitre saw, ensure the power is disconnected.
Review Questions
- What is a jig saw primarily used for?
- Describe how to start a plunge cut with a jig saw.
- What feature makes a reciprocating saw a very versatile tool?
- How is the size of a circular saw determined?
- What can be done to reduce saw dust spray into the operator’s face?
- What factors determine the smoothness of a cut when using a power mitre saw?
- What primary factor determines the selection of blade on a power mitre saw?
- What is the first step when changing a blade on a power mitre saw?
- List four safety precautions when using a mitre saw.
- Make a sketch of the following cuts:
- Mitre
- Bevel
- Compound mitre