A honing machine finishes bores with a rotating and reciprocating tool fitted with abrasive stones that expand against the bore wall. Vertical machines suit short, accurate bores such as engine blocks and gear bores; horizontal machines hone long tubes such as hydraulic cylinders.
Quick facts
- Main types
- Vertical (short bores), horizontal (long tubes), single-pass
- Bore range
- From about 3 mm (0.118 inch) up to several hundred mm
- Stroke length
- Short on vertical machines; several metres on horizontal tube honers
- Size accuracy
- About ±0.005 mm (±0.0002 inch) or better
- Finish
- About Ra 0.1–0.8 µm with cross-hatch
- Coolant
- Honing oil
Main parts
- Spindle that turns and strokes the honing tool
- Honing head with abrasive stones (aluminium oxide, silicon carbide, diamond or CBN)
- Feed system that expands the stones as material is removed
- Size gauging, often air gauging on modern machines
- Fixture to hold the part and let it float to follow the bore
Vertical or horizontal?
| Vertical | Horizontal | |
|---|---|---|
| Typical parts | Engine bores, gears, valve bodies | Hydraulic cylinder tubes, long barrels |
| Bore length | Short to medium | Up to several metres |
| Accuracy | Very high | High, depends on tube straightness |
Good to know
- Honing corrects size, roundness and straightness, not bore position
- Diamond and CBN stones suit hardened steel and cast iron in volume
- Air gauging lets the machine stop exactly at size
- Fixtures must let the part float so the tool follows the bore
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Questions
- What does a honing machine do?
- It finishes the inside of a bore to an exact size with a fine cross-hatched surface, and corrects roundness, taper and straightness left by boring.
- Which stones are used for honing?
- Aluminium oxide for soft steels, silicon carbide for cast iron and non-ferrous metals, and diamond or CBN for hardened steel and long production runs.
- Can a honing machine do hydraulic cylinder tubes?
- Yes, on a horizontal tube honing machine with a long stroke. Many tube makers use skiving and roller burnishing instead for speed, and honing for precision bores.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 16 October 2026.