A reamer is a rotary cutting tool used to enlarge and improve the accuracy of pre-drilled holes. Drilling a hole often leaves surface defects, such as irregularities and misalignment.

A reamer is designed with a series of cutting edges, typically spiral (but sometimes straight), to eliminate these defects, resulting in a smooth, precise, and dimensionally correct hole, typically to an H7 tolerance.

Reamers are particularly crucial in applications where precision is crucial, most commonly in the aerospace, automotive, and medical industries, as well as in fasteners and fixtures that require a series of precise positioning points.

Reamers are commonly used in a variety of applications, but the most common ones are enlarging drilled holes to specific sizes, deburring holes, and preparing holes for thread cutting.

Types of Reamers▼

There are many different types of reamers, each with its own specific uses. The most common types include:

Machine reamers:

Machine reamers, also called chuck reamers, are general-purpose cutting tools available in a variety of sizes and materials, including high-speed steel (HSS), carbide-containing steel, and HSSE (high-speed steel with cobalt). The type of material used depends on the specific application.

Typically, reamers are wide and have either a straight or Morse taper shank. Straight shank reamers are clamped in a collet chuck, drill chuck, or hydraulic chuck, while Morse taper shank reamers are clamped in a Morse taper chuck or in the tailstock of a lathe. Machine reamers typically have standard shank sizes, while reamers typically have shank sizes that are parallel to the diameter.

Hand Reamers:

Hand reamers are manually operated. They are typically used for light-duty hole-reaming operations, such as widening and smoothing previously machined holes, or reamers for worn or damaged holes. Hand reamers are also used for small holes where a machine cannot reach. Because carbide reamers are not suitable for manual operation, hand reamers are typically only available in HSS (high-speed steel).

These types of reamers are generally inexpensive and easy to use. However, compared to machine reamers, they are slow because all operations must be done by hand. If used improperly, such as due to user error, they can damage the hole. Hand reamers have a square design on the top of the shank so they can be used with a tap wrench.

Tapered Reamers:

Tapered reamers are used to ream holes with the same taper as dowel pins. Reamers are used to ream holes that have been drilled (or reamed) in workpieces. The primary purpose is to improve hole accuracy and reduce surface roughness. They are used for finishing and semi-finishing holes, typically with minimal stock removal. They have a tapered shank that matches the taper. The reamer's taper ensures a precise fit within the hole, while the cutting edge ensures a smooth, burr-free hole.

Taper pin reamers are typically made of high-speed steel (HSS) or carbide. HSS reamers are a good choice for general-purpose hole reaming, while carbide reamers are more suitable for reaming hard materials.

Adjustable Reamers:

Adjustable reamers are reamers that can be adjusted to different sizes. Because of this, they are very versatile and can be used for a variety of reaming operations. Adjustable reamers are typically made of high-speed steel (HSS) or carbide.

Adjustable reamers have a shank that can be adjusted by loosening one nut and tightening another. This allows the reamer to be expanded to the desired size. Adjustable reamers are typically used for light-duty hole enlargement, such as widening and finishing drilled or punched holes. As the cutting edge wears, you can adjust it slightly to restore it to its original size, unlike a conventional reamer, which becomes unusable once worn.

Modular Reamers:

Modular reamers are reamers with separate cutting heads that can produce holes of varying sizes. This makes them more precise than adjustable reamers, but they can also be more expensive. They are typically made of high-speed steel (HSS) or carbide. HSS reamers are a good choice for general-purpose reaming, while carbide reamers are better suited for machining harder materials.

Modular reamers typically have a threaded shank with a precise taper for accurate positioning onto modular adapters, allowing the reamer to be easily changed depending on the required size or material being reamed. Modular reamers were introduced in response to rising tool cost pressures, and they offer a high degree of flexibility and reduce the frequency of tool changes that fluctuate over time.