Reaming is a precision machining operation that removes a thin layer of material to improve hole size, shape accuracy, and surface finish. This process is widely used in manufacturing to ensure tight tolerances and consistent bore geometry across high-volume production runs.
Understanding the reaming process in manufacturing helps engineers choose the right tools, speeds, and coolants to achieve reliable quality while minimizing rework and scrap.
| Aspect | Details | Benefit | Typical Range |
|---|---|---|---|
| Operation Type | Internal finishing using multi-edge reamers | Size accuracy and smoother bore | Holes from 3 mm to 300 mm |
| Material Compatibility | Steel, stainless steel, aluminum, cast iron, brass, composites | Versatile across metals and engineered plastics | Most common machining sectors |
| Tolerance Capability | IT7 to IT9 (ISO 286) with repeatability | Consistent hole dimensions | ±0.02 mm typical |
| Surface Finish | Ra 0.8–3.2 μm depending on tool and feed | Reduced need for downstream honing | Controlled by feed and tool entry |
Basics of Reaming
How Reaming Differs from Boring
Reaming removes a small amount of material compared to boring, which is used for heavier material removal. While boring can size a hole substantially, reaming is primarily a finishing process that improves size, form, and texture after drilling or boring.
Straight vs. Tapered Reamers
Straight reamers are designed for through holes, whereas tapered reamers suit blind holes and applications requiring a locking fit. Choosing the correct style reduces breakage and improves feature control.
Tooling and Workpiece Setup
Reamer Types and Geometry
Hand reamers offer manual control for low-volume jobs, while machine reamers suit higher throughput. Spiral-point reamers push chips ahead, blind reamers contain chips within the body, and pull reamers use a tapered lead for smooth entry in through holes.
Hole Preparation and Alignment
Drinking-sized holes should be drilled using a drilled-to-size approach, leaving 2–5% extra material for reaming. Proper alignment with steady support prevents out-of-roundness and scoring, especially in longer bores.
Process Parameters and Control
Speed, Feed, and Coolant Selection
Lower speeds preserve tool life, while feed rates balance metal removal and surface quality. Through-feed operations suit powered reamers, whereas hand operations require careful control to maintain size and avoid chatter marks.
Chip Evacuation and Quality Checks
Effective chip removal prevents clogging, scoring, and reamer damage. Inspecting hole size with calibrated bore gauges and surface finish with comparators or profilometers ensures conformance to drawing specifications.
Advanced Considerations
Depth of Cut and Tool Life Management
Limiting depth of cut per pass reduces heat and extends tool life. Using coated carbide or specialized ceramics for abrasive materials allows tighter tolerances in demanding sectors such as aerospace and medical devices.
Automation and Process Integration
CNC reaming stations can be integrated into transfer lines for consistent bore quality across large batches. Sensor-based feedback helps adjust feeds and speeds on the fly, improving yield in continuous production.
Operational Excellence in Reaming
- Verify hole size and roundness before reaming to avoid overloading the tool.
- Select reamer style and entry method based on hole type and production volume.
- Use stable machine fixtures and precise alignment to prevent runout.
- Control feed and speed to balance material removal with tool wear.
- Employ effective chip evacuation through tool geometry and coolant flow.
- Perform regular tool inspections and measure output parts to maintain quality.
- Document process parameters for repeatability and continuous improvement.
FAQ
Reader questions
How do I determine the correct pre-reaming hole size?
Consult the reamer manufacturer’s chart for the material and desired finish, then drill to the recommended undersize allowance, typically 2–5% of the reamer diameter.
What causes reamer breakout or burrs at the hole exit?
Breakout often results from excessive feed, improper entry alignment, or insufficient back boring at the exit, which can be reduced by using a chamfered lead-in and backing up the exit side.
Can reaming be used on non-metallic materials such as composites?
Yes, diamond or coated reamers can machine composites, but low feeds, appropriate coolants, and controlled spindle speed are essential to avoid delamination and ensure clean hole walls.
How often should reamers be inspected and replaced?
Inspect for flank wear, chipping, and deformation after each use; replace when size exceeds tolerance or finish degrades, typically after a set number of cycles based on material and application.