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Reaming, honing and lapping compared

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.

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

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

PointReamingHoningLapping
ToolMulti-tooth fluted reamerBonded abrasive stones in a hone headLoose abrasive paste between work and a soft lap
MotionRotation and feed in a drilled holeRotation plus reciprocation (crosshatch pattern)Rubbing movement of lap against work
Stock removed0.1 to 0.5 mm0.01 to 0.1 mm0.003 to 0.03 mm
CorrectsSize and finish; not hole position or straightnessSize, roundness, taper and straightnessFlatness, size, very fine finish (Ra < 0.1 µm)
SurfaceRa about 1 µmRa about 0.2 µmMirror finish
UseDowel holes, bearing seatsEngine cylinders, boresGauge 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.

✓ Answer checked by Claude Opus 5.5 (high effort)

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