<P> Hacksaw blades are normally quite brittle, so care needs to be taken to prevent brittle fracture of the blade . Early blades were of carbon steel, now termed' low alloy' blades, and were relatively soft and flexible . They avoided breakage, but also wore out rapidly . Except where cost is a particular concern, this type is now obsolete .' Low alloy' blades are still the only type available for the Junior hacksaw, which limits the usefulness of this otherwise popular saw . </P> <P> For several decades now, hacksaw blades have used high speed steel for their teeth, giving greatly improved cutting and tooth life . These blades were first available in the' All - hard' form which cut accurately but were extremely brittle . This limited their practical use to benchwork on a workpiece that was firmly clamped in a vice . A softer form of high speed steel blade was also available, which wore well and resisted breakage, but was less stiff and so less accurate for precise sawing . Since the 1980s, bi-metal blades have been used to give the advantages of both forms, without risk of breakage . A strip of high speed steel along the tooth edge is electron beam welded to a softer spine . As the price of these has dropped to be comparable with the older blades, their use is now almost universal . </P> <P> The most common blade is the 12 inch or 300 mm length . Hacksaw blades have two holes near the ends for mounting them in the saw frame and the 12 inch / 300 mm dimension refers to the center to center distance between these mounting holes . </P> <P> The kerf produced by the blades is somewhat wider than the blade thickness due to the set of the teeth . It commonly varies between 0.030 and 0.063 inches / 0.75 and 1.6 mm depending on the pitch and set of the teeth . </P>

The commonly used standard length of hacksaw blade is