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Hacksaw parts and blade selection

Short answer

A hacksaw has an adjustable frame, a blade with teeth on one edge, a handle, and a wing nut for tensioning. Select pitch so at least three teeth engage the work: coarse (14 TPI) for soft metals, fine (24–32 TPI) for hard or thin materials. Cut on the forward stroke only, use full blade length, and keep the work clamped close to the cut.

Describe a hand hacksaw with its parts. How is the pitch of a hacksaw blade selected for different materials? State the rules for correct use of the hacksaw.

A hacksaw is a hand tool used to cut metal bars, pipes and sections. It consists of a frame holding a thin, hardened steel blade under tension.

Parts

  handle                       adjusting screw
   ___      ___________________   (wing nut)
  /   \____|                   |_____
 |    ____ |   blade  ----------     |
  \__/    |___________________|_____/
      frame (adjustable or solid)  pins at both ends
  • Frame: adjustable (takes blades of 250 to 300 mm) or solid.
  • Blade: high speed steel or low alloy steel, 250 or 300 mm between pin holes, with teeth on one edge.
  • Handle: pistol or straight grip.
  • Wing nut: tightens the blade; two pins hold it with the teeth pointing forward (away from the handle).

Selection of pitch (teeth per 25 mm)

Pitch (TPI)TeethMaterial
14CoarseSoft materials: aluminium, copper, mild steel (thick sections)
18MediumMild steel, cast iron, brass
24FineTool steel, pipes and tubes, angle iron
32Very fineThin sheets, thin-walled tubes, hard materials

Rule: at least three teeth must be in contact with the work at all times; otherwise the teeth strip and break.

The teeth are given a set (wave or alternate) so that the cut (kerf) is wider than the blade and the blade does not bind.

Correct use

  • Fit the blade with the teeth pointing away from the handle and tighten it well.
  • Clamp the work firmly, close to the cut.
  • Cut on the forward stroke only; lift the saw slightly on the return stroke.
  • Use 40 to 60 strokes per minute with light, even pressure, and use the full length of the blade.
  • Use a cutting lubricant for hard steels; start the cut with a file notch or at a small angle.

✓ Answer checked by Claude Opus 5.5 (high effort)

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