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How to Hone a Bore

Guide · Updated October 28, 2026

Honing removes a few thousandths of an inch to bring a bore to final size, roundness and finish. A rigid hone can correct size and shape; a flex or glaze-breaker hone only improves finish and follows the existing bore.

Check the bore

Set the dial bore gage with a ring gage or a mic on gage blocks before measuring. The free Gage Block Calculator builds the stack.

Step by step

Pick the hone: Rigid stone hone to size and true a bore; flex ball hone or glaze breaker for finish only.
Leave stock: Leave about 0.0005–0.002 in on diameter after boring or reaming.
Choose the grit: Coarser stones to remove stock, finer stones for the finish.
Flood with honing oil: Use honing oil, not dry or with water-based coolant unless the stones call for it.
Set speed and stroke: Run a steady RPM and stroke the full length, overrunning each end slightly.
Measure often: Stop, clean and gage the bore at top, middle and bottom in two directions.
Finish: Switch to the fine stones for the last few tenths and clean thoroughly.

Worked example

A 1.500 in bore was reamed to 1.4990 in and must finish at 1.5000–1.5005 in. That is 0.0010–0.0015 in to remove. With a rigid hone, take coarse passes to about 1.4998 in, checking with a bore gage set at 1.5000 in, then finish with fine stones to 1.5002 in. Readings top, middle and bottom: 1.5002, 1.5002, 1.5003 in, within tolerance and straight within 0.0001 in.

Crosshatch angle

The crosshatch angle comes from the ratio of stroke speed to rotation. Faster strokes for the same RPM make a steeper pattern. Engine cylinders often call for about 30–60° included; follow the spec for the part.

Common problems

Bell-mouthed ends come from overrunning too far or dwelling at the ends. Barrel shape comes from short strokes that never reach the ends. A flex hone will not fix taper or out-of-round; use a rigid hone or rebore.

Tips

Gaging: using a dial bore gage.
Before honing: reaming a hole.
Finish: surface finish basics.

FAQ

How much stock should I leave for honing?

About 0.0005–0.002 in on diameter.

Will a flex hone change bore size?

Only slightly; it improves finish and does not correct shape.

What oil should I use for honing?

A honing oil made for the stones.

What crosshatch angle do I want?

Follow the spec; many engines use about 30–60° included.

Why is my honed bore bell-mouthed?

The hone overran the ends too far or dwelled there.

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