---
title: "Reaming, honing and lapping compared"
subject: "Workshop Technology"
chapter: 5
key: "semester_2/workshop_technology:reaming-honing-lapping-differences"
source: https://www.bctengineer.com/q/semester_2/workshop_technology/reaming-honing-lapping-differences
site: BCT Engineering
---

# Reaming, honing and lapping compared

Workshop Technology · Chapter 5: Drills and Drilling Processes

- Asked in: year not given, 5 marks
- Video: [Honing, Lapping, and Buffing | Honing Process | Buffing and Lapping Processes](https://www.youtube.com/watch?v=4IM3B7GkcUM) — Study Central
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/workshop_technology/reaming-honing-lapping-differences
- Whole chapter: https://www.bctengineer.com/md/semester_2/workshop_technology/chapter-5

## Question

Differentiate between reaming, honing and lapping. Write the purpose of counterboring and countersinking.

## Short answer

Reaming uses a multi-tooth reamer for sizing; honing uses abrasive stones for bore geometry and finish; lapping uses loose abrasive for mirror finish. Counterboring makes a flat-bottom recess for bolt heads; countersinking makes a conical recess for flat-head screws.

## Answer

All three are finishing operations that bring a hole or surface to close tolerance and fine finish, but they differ in tool and action.

| Point | Reaming | Honing | Lapping |
|---|---|---|---|
| Tool | Multi-tooth fluted reamer | Bonded abrasive stones in a hone head | Loose abrasive paste between work and a soft lap |
| Motion | Rotation and feed in a drilled hole | Rotation plus reciprocation (crosshatch pattern) | Rubbing movement of lap against work |
| Stock removed | 0.1 to 0.5 mm | 0.01 to 0.1 mm | 0.003 to 0.03 mm |
| Corrects | Size and finish; not hole position or straightness | Size, roundness, taper and straightness | Flatness, size, very fine finish (Ra < 0.1 µm) |
| Surface | Ra about 1 µm | Ra about 0.2 µm | Mirror finish |
| Use | Dowel holes, bearing seats | Engine cylinders, bores | Gauge blocks, valve seats, lenses |

#### Counterboring
Enlarging the end of a hole to a larger diameter with a flat bottom so that a bolt head, nut or cap screw sits flush or below the surface. A pilot on the counterbore guides it in the original hole.

#### Countersinking
Making a conical enlargement at the mouth of a hole (usually 60°, 82° or 90°) so a flat-head screw or rivet lies flush. It is also used to chamfer and deburr holes and to make the centre-hole for lathe centres.

## Check yourself

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

1. Which operation uses bonded abrasive stones with rotation plus reciprocation, giving a crosshatch pattern?
   A. Reaming
   B. Honing
   C. Lapping
   D. Counterboring
   Answer: B. A hone head with abrasive stones rotates and reciprocates, leaving a crosshatch finish, e.g. in engine cylinders. (Key point: Honing motion)

2. Lapping is characterised by
   A. A multi-tooth fluted tool
   B. Loose abrasive paste between the work and a soft lap, giving mirror finish
   C. Large stock removal of 0.5 mm
   D. Single point tool boring
   Answer: B. Lapping uses loose abrasive on a lap, removing very little stock for flatness and mirror finish. (Key point: Lapping)

3. What reaming does NOT correct is
   A. Hole size
   B. Surface finish
   C. Hole position and straightness
   D. Dowel hole accuracy
   Answer: C. A reamer follows the drilled hole, so it fixes size and finish but not position or straightness. (Key point: Reaming limitation)

4. What is the purpose of a countersink?
   A. Make a flat-bottomed recess for a bolt head
   B. Make a conical enlargement so a flat-head screw lies flush
   C. Enlarge a hole to a precise size
   D. Thread a hole
   Answer: B. Countersinking gives a cone (60°, 82° or 90°) for flat-head screws; counterboring gives a flat-bottom recess. (Key point: Counterbore vs countersink)

## Related in Workshop Technology

- [Jigs and fixtures: purpose and differences](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Ajigs-and-fixtures-purpose-differences) — Workshop Technology, chapter 12
- [Annealing, normalizing and tempering of steel](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aheat-treatment-annealing-normalizing-tempering) — Workshop Technology, chapter 7

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