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The hacksaw is used to cut steel and other metals. It can also be used to cut plastics, although it is not normally used to cut woods. It is sometimes called an adjustable hacksaw because the length of the frame can be altered to hold blades of different sizes. Blades are supplied in two lengths, 250mm and 300mm. If the adjusting screw is unscrewed, the frame can be pushed into the handle so that the smaller blades fit the hacksaw.
Blades are also described by the number of teeth per inch (TPI). Blades have 14, 18, 24, 32 teeth per 25mm (inch). A blade with 14 TPI is coarse whilst a blade with 32 TPI is very fine.
Blades eventually wear or break and need replacing.
The blade can be replaced by loosening the wing nut adjuster until it comes off the two ‘studs’ that normally hold it in tension in the frame.
A blade should always be positioned with its teeth pointing away from the handle.
How to use hack saw
Selecting the correct blade for the material to be cut is important when setting up a hacksaw. High Speed Steel (HSS) blades are used for tough, resistant materials whilst High Carbon Steel blades are for general cutting.
Selecting the correct number of teeth per inch (25mm) is also important. The general rule is that at least three teeth should extend across the surface of the material to be cut.
The material should be carefully marked out. This normally involves using an engineers try square and scriber.
One hand holds the hacksaw handle. Notice how the index finger is used to support the handle and also points in the direction of cutting.
The other hand holds the frame, near the wing nut. Cutting/sawing should be carried out close to the jaws of the vice. This ensures that the metal does not flex or bend under the force of the hacksaw and the sawing motion.
When the metal has been cut, it will need filing. This removes sharp ‘burrs’ so that the metal can be handled safely, without the possibility of cuts to the hands.
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