---
title: "Hacksaw parts and blade selection"
subject: "Workshop Technology"
chapter: 2
key: "semester_2/workshop_technology:hacksaw-parts-blade-pitch"
source: https://www.bctengineer.com/q/semester_2/workshop_technology/hacksaw-parts-blade-pitch
site: BCT Engineering
---

# Hacksaw parts and blade selection

Workshop Technology · Chapter 2: General Hand Tools Used in the Workshop

- Asked in: year not given, 5 marks
- Video: [Hacksaw Blade and Frame Explained in Hindi | Types, Material, Pitch, Teeth Setting, Uses |](https://www.youtube.com/watch?v=7UygrvcTu2w) — MECHANICAL ENGINEERING SKILLS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/workshop_technology/hacksaw-parts-blade-pitch
- Whole chapter: https://www.bctengineer.com/md/semester_2/workshop_technology/chapter-2

## Question

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.

## 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.

## Answer

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
```text
  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) | Teeth | Material |
|---|---|---|
| 14 | Coarse | Soft materials: aluminium, copper, mild steel (thick sections) |
| 18 | Medium | Mild steel, cast iron, brass |
| 24 | Fine | Tool steel, pipes and tubes, angle iron |
| 32 | Very fine | Thin 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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How are the teeth of a hacksaw blade fitted in the frame?
   A. Pointing toward the handle
   B. Pointing away from the handle (forward)
   C. Either way, it does not matter
   D. Pointing downward only
   Answer: B. The hacksaw cuts on the forward stroke, so teeth point forward, away from the handle. (Key point: Blade fitting direction)

2. What rule governs the choice of blade pitch?
   A. At least three teeth must be in contact with the work at any time
   B. Only one tooth should touch the work
   C. Always use the coarsest blade
   D. Pitch must equal the work thickness
   Answer: A. If fewer than three teeth contact the work, the teeth strip and break, so thin sections need finer blades. (Key point: Pitch selection rule)

3. Which blade is best for thin sheets and tubes?
   A. 14 TPI coarse
   B. 18 TPI medium
   C. 24 TPI
   D. 32 TPI very fine
   Answer: D. Thin or hard sections need very fine teeth (32 TPI) so at least three teeth stay in contact. (Key point: Pitch for materials)

4. Why are hacksaw teeth given a set (wave or alternate)?
   A. To make the blade look straight
   B. To make the kerf wider than the blade so it does not bind
   C. To increase the blade hardness
   D. To reduce the number of strokes
   Answer: B. The set makes a cut wider than the blade thickness so the blade does not jam in the cut. (Key point: Purpose of set)

## Related in Workshop Technology

- [Vernier caliper and micrometer readings](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Avernier-micrometer-reading) — Workshop Technology, chapter 4

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- [Cost comparison of materials for a tie rod](https://www.bctengineer.com/question.md?key=semester_6%2Fmachine_design_i%3Amaterial-cost-tie-rod) — Machine Design I, chapter 2