Deep Hole Drilling Secondary Operations: Reaming, Honing, and Skiving

Deep Hole Drilling Secondary Operations

Deep hole drilling often produces holes that meet final tolerance and finish requirements — one of its primary advantages. However, when the as-drilled quality is insufficient, secondary operations can improve precision, surface finish, and geometry.

This guide covers the main secondary operations used after deep hole drilling, their capabilities, stock allowances, and when each is appropriate.

When Secondary Operations Are Needed

Condition	As-Drilled Quality	Secondary Operation
Tolerance too loose	±0.050 mm; need ±0.013 mm	Reaming or honing
Surface finish too rough	Ra 1.6 µm; need Ra 0.2 µm	Honing or roller burnishing
Straightness insufficient	0.15 mm/m; need 0.05 mm/m	Honing (corrects minor deviation)
Roundness needed	0.030 mm; need 0.005 mm	Honing
Surface defects present	Scoring, chatter marks	Honing or skiving

Reaming

Reaming is the most common secondary operation for improving hole diameter tolerance and surface finish.

Capability

Parameter	Standard Reaming	Precision Reaming
Tolerance improvement	±0.025 mm from drilled	±0.013 mm from drilled
Surface finish (Ra)	0.8–1.6 µm	0.4–0.8 µm
Stock removal	0.1–0.3 mm on diameter	0.05–0.15 mm
Depth ratio limit	< 15:1 (long reamers available)	< 10:1

Reaming Considerations for Deep Holes

Factor	Challenge	Solution
Tool alignment	Reamer follows drill path deviation	Use floating holder; pilot bushing
Chip evacuation	Chips pack in deep flutes	Use left-hand spiral reamer (pushes chips out)
Runout	Reamer amplifies any misalignment	Use hydraulic chuck; check < 0.005 mm TIR
Depth	Long reamers are flexible	Reduce feed; use support bushing

Recommended Stock Allowance

Drilled Diameter	Reaming Stock (mm per side)
3–6 mm	0.05–0.10 mm
6–12 mm	0.08–0.15 mm
12–25 mm	0.10–0.20 mm
25–50 mm	0.15–0.30 mm

Honing

Honing is the most effective operation for correcting geometry errors (straightness, roundness) and achieving very fine surface finishes.

How Honing Works

A honing tool with bonded abrasive stones expands against the bore wall as it rotates and reciprocates. This dual motion creates a crosshatch pattern that provides excellent oil retention for sealing surfaces.

Capability

Parameter	Honing
Tolerance	±0.005–0.013 mm
Surface finish (Ra)	0.05–0.4 µm
Straightness correction	0.01–0.02 mm per 300 mm
Roundness	0.003–0.008 mm
Stock removal	0.03–0.15 mm on diameter
Depth ratio limit	< 40:1 (long honing tools available)

Honing After Deep Hole Drilling

Drilled Condition	Honing Strategy	Result
Good straightness, needs finish	Light honing, 0.05 mm stock	Ra 0.2–0.4 µm
Moderate straightness, needs correction	Medium honing, 0.10 mm stock	Straightness improved 50%
Poor straightness	Not suitable — correct drilling instead	—

Stock Allowance for Honing

Diameter	Honing Stock (mm per side)
6–12 mm	0.025–0.050 mm
12–25 mm	0.025–0.075 mm
25–50 mm	0.050–0.100 mm
50–100 mm	0.075–0.150 mm

Honing vs. Deep Hole Drilling Quality

Quality Metric	As-Gun-Drilled	After Honing
Diameter tolerance	±0.025 mm	±0.005 mm
Surface finish	Ra 0.4–0.8 µm	Ra 0.05–0.2 µm
Straightness	0.08 mm/300mm	0.04 mm/300mm
Roundness	0.010 mm	0.003 mm

Skiving (Roller Burnishing Combined)

Skiving is a combined operation that uses a cutting head to remove a thin layer of material, followed immediately by rollers that burnish (smooth) the surface. It is typically performed on a dedicated skiving and roller burnishing (SRB) machine.

Capability

Parameter	Skiving
Tolerance	±0.013–0.025 mm
Surface finish (Ra)	0.1–0.4 µm
Stock removal	0.1–0.5 mm on diameter
Material removal	Cutting + plastic deformation
Depth ratio limit	< 40:1
Process	Single pass (combined tool)

Skiving Stock Allowance

Drilled Diameter	Skiving Stock (mm per side)
20–50 mm	0.15–0.25 mm
50–100 mm	0.20–0.35 mm
100–200 mm	0.30–0.50 mm

Roller Burnishing

Roller burnishing (also called surface rolling) uses hardened rollers to cold-work the bore surface, producing a very smooth finish through plastic deformation.

Capability

Parameter	Roller Burnishing
Surface finish (Ra)	0.05–0.20 µm
Diameter change	0.005–0.015 mm (expansion)
Process	Cold working (no material removal)

Best for: Improving surface finish without removing material. Does not correct tolerance or geometry errors.

ID Grinding

Internal cylindrical grinding is the most precise secondary operation but is rarely needed after deep hole drilling due to the difficulty of deep grinding.

Parameter	ID Grinding
Tolerance	±0.003–0.008 mm
Surface finish	Ra 0.1–0.4 µm
Depth ratio limit	< 5:1 (severe limitation)

Not recommended for deep holes. Grinding is limited to short bores due to grinding wheel deflection and cooling difficulties.

Process Selection Guide

Requirement	Best Method	Why
Tighter diameter tolerance	Reaming (moderate) or honing (precision)	Most common and cost-effective
Better surface finish	Honing or roller burnishing	Honing gives best finish; burnishing is faster
Improve straightness	Honing	The only secondary operation that corrects geometry
Improve roundness	Honing	Corrects lobing from gun drilling
Remove surface defects	Honing or skiving	Honing for light defects; skiving for deeper removal
Minimum stock removal	Roller burnishing	No material removal; cold working only
After BTA/ejector drilling	Honing (often needed)	BTA finish is rougher than gun drilling

Process Sequence Examples

Scenario 1: Gun Drilled, Needs Better Finish

Gun drill → Light hone
As-drilled:  ±0.025 mm, Ra 0.8 µm
After honing: ±0.013 mm, Ra 0.2 µm
Stock: 0.05 mm per side

Scenario 2: BTA Drilled, Needs Tight Tolerance

BTA drill → Ream → Hone
As-drilled:  ±0.075 mm, Ra 2.5 µm
After ream:  ±0.038 mm, Ra 1.0 µm
After hone:  ±0.013 mm, Ra 0.2 µm
Stock: 0.20 mm (ream) + 0.05 mm (hone)

Scenario 3: Gun Drilled, Maximum Precision

Gun drill → Hone
As-drilled:  ±0.025 mm, Ra 0.8 µm
After hone:  ±0.005 mm, Ra 0.05 µm
Stock: 0.05-0.10 mm per side

Summary

Secondary operations extend the precision of deep hole drilling beyond as-drilled capabilities. Reaming improves diameter tolerance at moderate cost. Honing corrects geometry errors (straightness, roundness) and achieves the finest surface finishes. Skiving removes more material in a single pass and produces good finish. Roller burnishing improves finish without removing material. For most deep hole applications, gun drilling followed by light honing provides an excellent balance of precision and cost.

For as-drilled tolerance and finish data, see deep hole drilling tolerances guide. For measurement methods, see deep hole measurement methods. For a complete overview, visit the precision and quality guide.