Editing Hacksaw (section)

== Design ==
[[file:Tool-hacksaw.jpg|thumb|left|Small hacksaw (also known as junior hacksaw). The teeth of the hacksaw blade point forward, away from the handle]]

Standard hacksaw blade lengths are {{cvt|10|to|12|in}}. Blades can be as small as {{cvt|6|in}}. Powered hacksaws may use large blades in a range of sizes, or small machines may use the same hand blades.<ref>{{cite book |last1=Burton |first1=Walter E. |title=Homemade Power Hacksaws for less than $20 |date=February 1964 |publisher=Popular Science |edition=February 1964 }}</ref>

The pitch of the teeth can be from fourteen to thirty-two teeth per inch (TPI) for a hand blade, with as few as three TPI for a large power hacksaw blade. The blade chosen is based on the thickness of the material being cut, with a minimum of three teeth in the material. As hacksaw teeth are so small, they are [[saw set|set]] in a "wave" set. As for other saws they are set from side to side to provide a [[wikt:kerf|kerf]] or clearance when sawing, but the set of a hacksaw changes gradually from tooth to tooth in a smooth curve, rather than alternate teeth set left and right.

Hacksaw blades are normally quite [[brittleness|brittle]], so care needs to be taken to prevent [[fracture#Brittle|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.

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 [[vise|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 welding|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.

The most common blade is the 12 inch or 300 mm length. Hacksaw blades have a hole at each end 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.<ref>Machinery's Handbook, 14th Edition, by Erik Oberg & F. D. Jones, The Industrial Press, 1952, pages 1390-1391</ref>

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&nbsp;mm depending on the pitch and set of the teeth.