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Reaming in CNC Machining: Reaming Definition, Reamer Tools, and Reaming vs Boring Explained
Release time:
Feb 06,2026
You already know the truth if you have ever purchased CNC machined components for robotics or medical devices.
It is rare that a part fails due to its shape. The holes are not sized correctly.
A hole that's slightly out of round, oversized, rough or tapered can cause a misalignment of an assembly, make noise in the robot joint or reduce the life expectancy of a medical component or aerospace component.
reaming has become one of the most important hole finishing processes in CNC machining.
This practical guide to suppliers from (YIXIN PRECISION, Shenzhen, China) covers:
- The true reaming Definition
- How the reamer works
- How to choose the best reamer
- boring vs reaming
- Reaming for CNC production parts is the best option
1) Definition of Reaming (What is Reaming?
Let's begin with the most popular question: reaming.
Reaming consists of removing small amounts of material from an existing hole to improve accuracy, surface finish and roundness.
Important detail:
It is rare to use reaming for creating a hole in solid material.
Instead, it uses after to create a hole.
The following is a list of the most recent drillings
circular interpolation (milling)
You can also find out more about the following:
Consider reaming the "final tune-up" for precision holes.
2) Why Reaming Matters (The Real Manufacturing Reason)
Reaming has three main benefits in production.
Consistent Hole Dimension
When drilling, holes are often left behind.
Slightly oversized
The taper is a slightly tapered shape
Due to tool wear, there may be differences in the quality of a batch.
Reaming is a great way to stabilize the final diameter.
Improved Surface Finish
The hole on the outside may be fine, but it is often contaminated inside.
Spiral marks
Tearing (especially in stainless-steel)
micro burrs
The reamed holes are smoother, and therefore better for bearings, sliding fittings, or pins.
The Roundness of the Corners is Improved
The holes in the drill can be oval or slightly oval.
Thin walls
long depth-to-diameter ratios
Harder Materials
Reaming can help correct these errors to a certain extent.
3) What Is a Reamer Tool?
reamer tools are multi-edged cutting tools designed for finishing holes.
A reamer is not a drill bit, which is designed to remove material aggressively.
Removes only a small amount of material
Uses multiple cutting edges to increase stability
improves surface finish
Better size repeatability
A reamer does not cut "strongly". It is "precision" tool.
It is important to understand the process that takes place before reaming.
4) Common Types of Reamer Tools in CNC Machining
The most common reamer tool used in CNC production includes:
1)Straight Flute Reamer
Common for through holes
Simple, stable and widely used
When chip evacuation is simple, it's best.
2) Spiral flute Reamer
Blind holes are ideal for blind holes
better chip evacuation
Stainless steel and titanium are often superior.
3) Carbide Reamer
longer tool life
Better for volume production
More stable materials
4) HSS Reamer
Lower cost
Good for small batches
Regrinding is easier
The selection of reamer tools at YIXIN PRICE is based:
Hole diameter and depth
Tolerance requirement
Material type
production quantity
Risk of chattering and chip packing
5) Reaming vs Boring (What’s the Difference?)
This is the most important comparison in hole machining.
Boring and reaming can both improve the quality of a hole, but their roles are different.
Reaming vs Boring: Simple Explanation
Reaming removes a small amount material using a multi-edge reamer.
Boring enlarges and corrects a hole using a single-pointed cutting tool (boring bars).
Engineers and buyers should know the key differences
| Features | Reaming | Boring |
|---|---|---|
| Tool Type | Multi-edge reamer | Single-point boring bar |
| Material Removal | Very small | Large to medium |
| Best Use | Final Sizing | Expanding and Correcting |
| Fixing the hole position | Limited | You can also read: |
| Tolerance Typical | H7 (common) | The height of the can be extremely high |
| Cost per Hole | Low-cost | Higher |
When Reaming is the Best Choice
When to choose reaming
The hole is almost the final size
You need to repeat the diameter and finish
You want high productivity
You need to ensure that pins, bushings and bearings are all the same size.
When boring is the better choice
Select boring when:
You need to remove additional material
You need to correct coaxiality
You need to be able to control the true position with more strength
The hole is too deep or large. It may need geometry correction
Supplier recommendation:
The best way to fix many critical holes is:
Drilling, Boring, and Reaming (Final Finish)
6) Typical CNC Reaming Process (Step by Step)
It is not enough to "run the reamer" and "hope."
This requires a controlled order.
Step 1: Prepare the Pre-Hole
This hole is slightly smaller than the original size.
The following is a list of the most recent drillings
or circular milling
Step 2: Enter the correct Reaming Allowance
The #1 factor in determining success is this.
The allowance is too low
The reamer cuts instead of rubbing
Surface finish gets worse
The hole size is inconsistent
The allowance is too high
Chatter is a common occurrence.
tool life drops
The hole can grow to be oversize
Step 3: Reaming at the Correct Speed/Feed
Reaming is needed:
stable feed (no hesitation)
Correct coolant strategy
The rigid tool holding
Step 4: Inspection
Inspection can be performed in different ways depending on the tolerance.
plug gauges (Go/No-Go)
Bore gauges
CMM reports of position and coaxiality
YIXIN Precision checks critical reamed-holes in the process to avoid batch drift.
7) Common Reaming Problems (And How to Avoid Them)
Although reaming may be common, it's not "easy."
Here are some of the most common issues that arise in real life.
Problem 1: Reamed Hole Oversize
Causes:
incorrect allowance
Wear reamer
Tool Runout
built-up edge in aluminum
Poor lubrication
Problem 2: Reamed Hole Taper
Causes:
alignment error
tool deflection
Fixation that is unstable
The wrong retract cycle
Problem 3: Poor Surface Finish
Causes:
Too little stock can cause rubbing
Chip packing
The wrong coolant
Poor flute selection
Problem 4: Chatter marks
Causes:
excessive tool overhang
Too high spindle speeds
Unstable part clamping
Professional CNC suppliers prevent these issues by:
Correct reamer tool choice
Optimized parameters by material
Stable Workholding
Controlled inspection intervals
machine condition monitoring
8) Reaming in Different Materials (What Changes)
Different materials behave differently when reaming a hole, especially if the hole is large or the tolerance tight.
Aluminum (6061 / 7075)
Risk: Oversize hole - built-up edge
Best Practices
Sharp carbide reamer
Correct coolant
Avoid rubbing
Stainless Steel (SUS304 /SUS316)
Risks: Main risks: tears and rough finishes
Best Practices
Spiral flute reamer
Coolant with higher lubricity
Controlled speed and stable feed
Titanium (Ti-6Al-4V/TC4)
Heat and galling are the main risks
Best Practices
Carbide reamer
Conservative cutting speed
Strong coolant flow
correct stock allowance
9) Where Reaming Is Used in Real CNC Parts
Reaming is a common practice at YIXIN PRECISION.
robot joint bearing holes
precision locating pin holes
Medical device assembly holes
Aerospace brackets with tightly-fitted holes
Automation housings and fixtures
optical aligning holes
Reaming is mandatory in these applications.
The difference between a smooth assembly and costly rework is often a matter of seconds.
10) Why Choose YIXIN PRECISION for Reaming and Precision CNC Machining?
It takes more than just a reamer to ream. You need a complete system.
stable machines
Correct tooling
Experienced Process Planning
Inspections that are reliable
Yixin Precision is a manufacturer of precision CNC parts.
Strong Manufacturing Capability
CNC milling, turning and turning
Machining on 3-axis, 5-axis and 4-axis
Custom parts from prototype to mass production
Quality Control for Critical Holes
Plug gauges and boregauges for fast control
CMM inspection for geometrical requirements
In-process inspection prevents size drift
Experience in High-Standard Industries
Robotics
medical devices
Aerospace
You can also find out more about the automation of your home.
precision instruments
One-Stop Manufacturing Service
We also support
Sheet metal fabrication
die casting
injection molding
Surface finishing
assembly
It reduces the complexity of suppliers and allows customers to shorten their lead times.
Final Thoughts: Reaming Is Small, But It Controls the Fit
The reaming operation is one of the smaller operations of CNC machining, but it has a significant impact on the functional characteristics of a part.
If your design requires:
Smooth assembly
Stable bearings
accurate locating holes
reliable production repeatability
Consider reaming early in your manufacturing plan.
YIXIN PRCISION can support your next project, from engineering review to stable manufacturing.
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2025-12-31
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