Tom Beaumont

Product Training Manager

18 years engineering experience, specializing in 3 & 4 axis CNC milling, turning and horizontal boring.

Reamers are a vital tool for any engineer or machinist. They are used to enlarge and improve the precision of drilled holes, leaving a smooth, accurate finish to a certain tolerance.

In this blog, we will discuss the different types of reamers, explore the importance of different reamer substrates, and explain the significance of various reamer geometries. By understanding the different types of reamers and their applications, you can ensure that you are using the right tool for the job.

What Is A Reamer?

A reamer is a rotary cutting tool used to enlarge and improve the precision of a pre-drilled hole. When a hole is drilled into the material there are often imperfections left on the material surface, such as irregularities and misalignments. Reamers have been designed with a series of cutting edges, often in a spiral pattern (but sometimes in a straight flute geometry too), to remove these imperfections, resulting in a smooth, accurate and correctly sized hole typically to a h7 tolerance.

Reamers are crucial in applications where precision and accuracy are essential, most commonly in industries such as aerospace, automotive, medical industries and people manufacturing jigs and fixtures where a series of precision location points will be required.

Reamers are often used in a wide variety of applications but the most common are enlarging drilled holes to a specific size, deburring drilled holes, and preparing holes for threading applications.

Types of Reamers Expained

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

Machine Reamer

Machine reamers, also known as chucking reamers, are general-purpose cutting tools that are available in a variety of sizes and materials, including high-speed steel (HSS), solid carbide, HSSE (cobalt). The types of material depend on the specific application.

Typically, chucking reamers are wide with a straight or morse taper shank. The straight shank reamers are held in a collet chuck, drill chuck or hydraulic chuck, while the morse taper shank reamers are held in a morse taper chuck or held in the tailstock on a lathe. Machine reamers often have standard-sized shanks, whereas chucking reamers often have shank sizes that are parallel to the diameter.

Hand Reamer

A hand reamer is a type of reamer that is operated by hand. They are typically used for light-duty reaming, such as enlarging and smoothing holes that have previously been reamed or holes that are worn or damaged. They are also used for reaming small holes that are not accessible by machine reamers. Hand reamers are usually only available in HSS (high-speed steel) due to carbide not being suitable for manual operations.

These types of reamers are typically inexpensive and easy to use however, they can be slow to use in comparison to machine reamers as all operations have to be done by hand. Due to the fact that they typically have to be used by there is an element of user error that can damage a hole if not used correctly. Hand reamers will have a square drive at the top of the shank so they can be used with a tap wrench.

Taper Pin Reamer

A taper pin reamer is a type of reamer that is used to create precise holes for a tapered pin. They have a tapered shank that matches the taper of the taper pin. The taper of the reamer ensures that the taper will fit precisely into the hole, and the cutting edges ensure that the hole is smooth and burr-free.

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

Adjustable Reamer

An adjustable reamer is a type of reamer that can be adjusted to different sizes. Because of this, they are extremely versatile and can be used in a variety of reaming applications. Adjustable reamers are typically made of high-speed steel (HSS) or solid carbide.

Adjustable reamers have a shank that can be adjusted by loosening one nut and tightening the other. This allows the reamer to be expanded to the desired size. Adjustable reamers are typically used for light-duty reaming, such as enlarging and smoothing holes that have been drilled or punched. They are also good because as the cutting edges wear down you can keep adjusting them bigger slightly to bring it back to size whereas a solid reamer once its worn it’s no longer fit for purpose.

Modular Reamer

Modular reamers are a type of reamer with individual cutting heads that can be swapped out to create different sized holes. This makes them more accurate than adjustable reamers, but they can also be more expensive. They are typically made of high-speed steel (HSS) or solid carbide. HSS reamers are a good choice for general-purpose reaming, while solid carbide reamers are better suited for reaming hard materials.

Modular reamers typically have a screwed shank that has a precision ground taper for accurately locating onto a modular adapter, changeable heads can be easily replaced depending on the size required or the material that needs reaming. Modular reamers were introduced to counter rising tool costs, they offer a high degree of flexibility and reduce tool change over time.

Reamer Substrates

Reamers are typically made from high-speed steel (HSS) or carbide.

Carbide and HSS are both strong and durable materials, but they have different properties that make them better suited for different applications.

Carbide: Carbide is a very hard material that is made from tungsten carbide and cobalt. It is often used in cutting tools because it can withstand high temperatures and wear. Carbide reamers are a good choice for reaming hard materials, such as steel, stainless steel, HRSA’s and cast iron. They also run at faster feed rates with much longer tool life providing the right cutting conditions are applied.

HSS: HSS is a less expensive material than carbide, but it is still strong and durable. It is made from tungsten, chromium, and vanadium. HSS reamers are a good choice for general-purpose reaming and for reaming softer materials, such as softer steels, aluminium and brass.

HSS vs Carbide Reamers

The best reamer substrate for you will depend on your specific needs and requirements. If you need a reamer that can withstand high temperatures and wear, carbide is a good choice. If you are on a budget, HSS is a good option.

Reamer Geometries

The type of reamer geometry you choose will depend on the specific application.

Left-Hand Spiral: Left-hand spiral reamers are designed for reaming through holes, the spirals help push the swarf out through the holes to prevent interference between the cutting flutes and material, left-hand spirals cope well with interrupted cuts like cross holes or keyways.   

Right-Hand Spiral: Right-hand spiral reamers are designed to cut blind holes as the flutes will draw the swarf out of the pre-drilled hole, this prevents the swarf from being packed into the bottom of the blind hole and prevent the reamer from becoming damaged. Right-hand spirals are also effective when coming in contact with cross holes or keyways.   

Straight Flute: Straight flute reamers are the most common type of reamer. They are a good choice for general-purpose reaming and will perform well in both blind and through holes.  

Spiral Flute vs Straight Flute Reamer

The best reamer geometry for you will depend on your specific needs and requirements. If you are reaming a blind hole, a right-hand spiral reamer is a good choice. If you are reaming a through hole, a left-hand spiral reamer is a good choice. If you are reaming softer materials, a straight flute reamer is a good choice.

Step By Step Guide On How to Use A Reamer

Typical reaming operation using a HSS drill and reamer on a CNC milling machine (blind hole)

Step 1: Select the correct reamer. The reamer you select should be the same size as the finished hole you want to create. For example, if you want to create a Ø4.5mm h7 hole, you will use a 4.5mm reamer.

Step 2: Create a location divot. The reamer will work best if you drill a location divot using a spot drill (e.g. D4306060). This will help to centre the drill and prevent it from wandering. The pilot hole should be 0.2mm smaller than the reamer.

Step 3: Drill the hole. The finished hole size we are wanting to create is Ø4.5mm h7, before we do this we need to drill (e.g. DLGP195043) a hole that is Ø4.3mm (0.2mm smaller than the desired hole size)

Step 5: Ream the hole to the desired depth, using a Ø4.5mm reamer (e.g. 30104084).

Conclusion

The type of reamer you choose will depend on the material being reamed, the desired finish and hole tolerance, your machining capabilities, and the application.

As a general rule of thumb, Carbide should be considered if a higher-performing, more accurate result is required, providing you have the budget and machining capabilities. HSS would be a suitable option for more manual applications or general-purpose reaming of softer materials or for those on a budget. Hand reamers are available for this without machining capabilities.

For expert advice on choosing the right reamer for your application please contact our technical team on 01924 869 615 or email sales@cutwel.net

Straight or spiral flute HSS hand reamers for general steel, stainless steel, cast iron & non ferrous.

Carbide machine reamers for producing high tolerance holes on a wide range of materials.

Cost effective reaming for medium to large diameters from 8-40mm with modular reamer heads.