What is Reaming | How to Use

Making a hole in the prototype CNC machining process on a product is very common because these holes can be used for assembly and positioning the part to another. Reaming is widely used in machining to have high-precision hole dimensions. today, in this blog, we explain what reaming is and how it works.

What is Reaming?

Reaming is a method by which the reamer cuts the trace metal layer from the hole wall of the workpiece to improve its dimensional accuracy and the surface quality of the hole. Reaming is widely used in production because, for smaller holes, reaming is a more cost-effective and practical machining method than internal grinding and fine boring.

What Is the Purpose of Reaming?

Improve Hole Precision

Generally, the rough reaming allowance is between 0.35mm to 0.15mm, and the fine reaming allowance is between 0.15mm to 0.05mm. the dimensional accuracy of reaming can generally reach the IT9 ~ IT7 level.

Achieve Adequate Surface Roughness

The surface roughness of reaming, Ra is generally 3.2~0.8. Reaming is usually processed at a lower cutting speed (v < 8m/min when machining steel and cast iron with high-speed steel reamers) and uses appropriate cutting fluids for cooling, lubrication, and chip removal to help prevent chip accumulation and achieve better roughness.

How is reaming done step by step

Step 1: Selecting the Right Reamer

The choice of reaming allowance directly affects the quality of reaming. The reaming allowance should not be too large or too small. Because the reaming allowance is too small, the original machining tool marks cannot be removed, and the reaming quality cannot meet the requirements. When the allowance is too large, the cutting load of each tooth will be increased, destroying the stability of reaming, increasing cutting heat, causing the diameter of the reamer to expand, and the hole diameter will also expand. Choose your Reamer diameter and reaming allowance as below table:

Step 2: Secure Workpiece Clamping and Alignment

Ensure secure and precise clamping and positioning of workpieces to maintain reamer-to-hole coaxiality.

Step 3: Clean and Lubricate the Reamer

Clean the reamer tool body and apply an adequate amount of cutting fluid both inside the hole and on the reamer.

Step 4: Tool Change and Setting

According to the tool data in the programming work instruction book, replace the tool to be processed and let the tool contact the height measuring device placed on the datum surface. When the red light of the measurement is on, set the relative coordinate value of this point to zero and turn on the device. Move the tool to a safe position, manually move the tool down 50mm, and set the relative coordinate value of this point to zero, which is the Z-axis zero position.

Step 5: reaming Parameters Setup

Spindle speed setting: N=1000V/(3.14D)

• N: Spindle speed (rpm/min)
• V: Cutting speed (m/min)
• D: Tool diameter (mm)

Processing feed speed setting: F=N×M×Fn

• F: Feed speed (mm/min)
• M: Tool tolerance
• Fn: Cutting capacity (mm/rev)

The setting of cutting amount per edge: Fn=Z×Fz

• Z: Number of cutting edges
• Fz: Cutting amount of each edge of the tool (mm/ revolution)

Step 6: reaming

In the reaming process, it is necessary to first use the center drill to locate, and then drill with a drill bit 0.5~0.3mm smaller than the drawing size, and finally reaming with a reamer. Control spindle speed within 70~180rpm/min when reaming.

Step 7: Reamer Maintenance

Clean the reamer after use and apply oil. When placed, pay attention to protect the blade to prevent damage from collision

What is a reamer?

A reamer is a type of rotary cutting tool used in metal parts machining for enlarging and finishing to accurate dimensions holes that have been drilled, bored, or cored.

Different Types of Reamers

Hand reamer

A hand reamer has a longer taper or lead in at the front than a machine reamer. This is to compensate for the difficulty of starting a hole by hand power alone. Hand reamers enlarge or finish an existing hole in a metal workpiece to a desired size.

Machine Reamers

These reamers are similar to hand reamers, except that the shank is tapered

Spiral-Fluted Reamers

Spiral-fluted reamers are special-purpose reamers that are ideal for hard-chipping materials like stainless steel. Thanks to their spiral-shaped flutes, these hole reamers evenly distribute cutting forces, enabling them to effectively cut through tough materials.

Chucking reamers

Chucking reamers are general-purpose cutting tools that provide superior wear and tear resistance at high temperatures. They come in a straight shank or a morse taper shank and are used for CNC lathes tools or drill presses.

Expanding Reamers

Expansion reamers are used to enlarge or finish an existing hole to a precise tolerance or size. it can be reground to its original size due to They have an adjustment screw that expands the size of the cutting head.

Adjustable Reamers

Adjustable reamers are designed to ream odd-sized holes. In these reamers, separate blades are inserted in the grooves provided in the body of the reamer. The blades can be moved up or down of the reamer.

Tapered Reamers

Taper pin reamers are used in metalworking applications to enlarge, finish, or shape holes for a precise fit when installing taper pins into the hole. These reamers are used to finish the taper holes for cutting the taper things used to secure the collars, and pulleys to the shaft.

Shell Reamers

High-speed steel Shell Reamers are multi-fluted, end-cutting tools used to enlarge previously formed holes to a precise diameter with a smoother finish.  These reamers are however not very rigid and accurately inserted teeth or plates in shells further reducing the cost of reamers that can tip with cemented carbides.

Guidelines for reaming operations

Feeds and Speeds for Reaming

• Adjust feeds and speeds based on material type, machine specifications, and desired finish and precision. Typically, reaming is performed at about two-thirds of the feeds and speeds used for drilling in the same material.
• Metal reaming usually requires higher feeds compared to drilling, often running at 200% to 300% of drill feeds. Avoid excessively low feeds to prevent reamer wear; it should cut rather than rub or burnish.

Precise Alignment

• Perfect alignment of the spindle, bushing, reamer, and the hole to be reamed is critical. Ensure the helix angle aligns correctly with other parameters to minimize reamer wear and maintain hole accuracy.
• For oversized, tapered, or irregularly shaped holes, verify alignment parameters. Adjustable holders can help mitigate alignment errors.

Reamer Regrinding

• Maintain cutting tools to prevent excessive dullness before sharpening or replacement. Regularly regrind the chamfer on a reamer before it becomes too worn or ineffective.
• Focus regrinding efforts on the chamfer or entering taper. Ensure even sharpening of each flute to avoid oversizing. Hand sharpening is not recommended due to the challenge of maintaining uniform cutting edges.

Stock Allowance

Proper stock allowance is crucial for reamer machining. Typically, it’s about .010″ for a ¼” hole, .015″ for a ½” hole, and up to .025″ for a 1½” hole. Hand reaming requires a smaller allowance, typically .001″ to .003″, owing to difficulties in handling larger stock.

Chatter Prevention

Chatter during reaming operations can compromise hole finish and reamer effectiveness. To minimize or prevent chatter:

• Ensure machine rigidity.
• Reduce reamer clearance.
• Avoid excessive reamer overhang.
• Use an appropriate feed rate.
• Lower cutting speed while increasing the feed rate to minimize vibrations and maintain quality hole finishes.

Reaming Vs. Boring Vs. Drilling: What Are the Differences?

Reaming, boring, and drilling can all used to create holes, here is a comparison table to show the difference between them.

Precision CNC Machining Services

Achieving the perfect hole in your machined parts is not hard, but it can also be a complex task. With decades of machining expertise, KUSLA can manage all kinds of hole machining processes and provide you with precision machined parts. Contact us today to get an instant quotation.