Reamers are finishing tools, used to produce a smooth hole in a hole that has been already drilled, effectively causing it to have a more precise size and finish instead of the one left by the drill.
Both cylindrical and tapered holes may be made by a reamer.
Reamed holes are employed in work of tool and die making, in parts of combustion engines, in holes for airframe fasteners, and in firearms work.
In this short article, we are going to learn what they are and how they work, the different types of reamers we have available today, and how to use them to get the job done efficiently and accurately.
What Are Reamers and How Do They Work?
When a hole is required in a part, it is usually cut by a drill. But drills do not produce holes of precise dimensions; their function is to remove large amounts of material quickly. Such processes are perfectly adequate for holes there need not be of a precise size and with smooth surface finish; for instance, holes for fastening implements.
On the other hand, the reamer is used to enlarge an existing drilled hole to a given size with a close tolerance. Reamers are, therefore, designed only to remove a small amount of material, and they are shaped as either straight or helical flutes.
A reamed hole may be produced either by hand or machine; if the greatest degree of precision is desirable, the hole should be produced by a machine.
Hole reamers may be made of HSS, carbide, and high-alloy steel. The reaming of holes is a finishing process.
What is a Reamer Tool?
A reamer is a tool for enlarging or finishing to size, a drilled, bored, or cored hole to a fine finish and an accurate dimension.
A reamer is a multi-tooth cutter cutting a correspondingly small amount. There are many kinds of reamers for different operations and purposes. The more or less commonly used reamer details in I.S. specifications are given below.
Parts of Reamer
Elements of a reamer:
- Axis. The longitudinal centre line of the reamer.
- Back Taper. The taper is towards the entering end, that is, less diameter per 100 mm length from the entering end of the reamer to the shank.
- Bevel Lead. The angular cutting portion at the end of the inlet to help the reamer into the hole. It is not furnished with a circular land.
- Body. The portion of the reamer which extends from the entering end to the beginning of the shank.
- Circular Land. The surface rounded on a cylinder adjacent to the cutting edge, on the leading edge of the land.
- Clearance. Primary: The portion of the land broken away for clearance immediately behind the cutting edge. Secondary: The portion of the land broken away for clearance directly behind the primary clearance or circular land.
- Cutting Edge. The cutting edge is obtained by the intersection of the surface of the face with the circular land, or the land as left by the provision of primary clearance.
- Face. The portion of the surface of the flute adjacent to the cutting edge upon which the chips as cut from the work impinge.
- Flutes. The grooves in the body of the reamer are to form cutting edges, to allow the chips to escape, and to give access to the cutting edges for fluid.
- Heel. The edge is formed by the intersection of the surface left by the provision of secondary clearance with the flute.
- Land. The portion of the body left standing between the flutes, the surface, or surfaces, lying between the cutting edge and the heel.
- Pilot. A portion of the body, only ground on a cylinder, at the entering end of the reamer to keep the reamer in line.
- Recess. That portion of the body which is cut to a smaller diameter than the cutting edges, the pilot or guided diameter.
- Shank. That portion of the reamer by which it is held and turned.
- Diameter. The maximum cutting diameter of the reamer at the inlet end.
Different Types of Reamers
There are quite a few different reamers available, each suited for a particular task. Some of the more common reamer types are below:
Chucking Reamer
These are by far the most common reamers. They may have a straight shank or taper. Sometimes called machine reamers also. The flutes may be straight or helical.
These types of reamers are usually inserted into a CNC or manual drill press or lathe mill chuck or collet, hence the name. Tip may be chamfered at 45°.
A chucking reamer is used when the hole needs to be enlarged from an already drilled hole, to a more accurate dimension and with a finer tolerance.
Hand Reamer
These are also designed to be held in the hand without a machine, so not with CNC machines. The square at the rear end of the shank to attach to a tap wrench or spanner.
The front of the reamer is slightly tapered, making if self-aligning in the hole for easier use. Hand reamers are used for light cutting jobs and are not as accurate as machine reamers, as there is always room for human error, so not suitable for use in applications with tight tolerances.
Shell Reamer
Usually of a hollow cylinder geometry, with straight flutes. Used on CNC and manual machines. Also uses helical and twisted flutes. The ID of the reamer is sized to fit over an arbor.
The by far best advantage of a shell reamer over regular reamers is that only the cutting edges need to be replaced when worn, not the whole shank. Another advantage is that due to the slots on the rear of the reamer they cannot spin while reaming, the lugs can engage with an arbor.
Best used for holes of over 0.75” size. Use of a left-hand spiral flute if the hole is a blind one.
Ring Reamer
This type typically has several cutting bits secured to the periphery of a ring, much like a face mill is arranged. Ring reamers are used at high speeds, for the most part on larger diameter holes.
The limited expansion, which is a general feature of most of the ring reamers, restricts tool wear and, with greater accuracy, makes for a more lasting tool.
Expansion Reamer
Expansion reamers are made for increasing their diameter by turning a screw, which displaces the cutting edge outward generally in a radial direction. This expansion enables the tool to wear and compensate for same, as well as to make different diameter holes in small increments.
The modular form of these reamers, which are not as tough as the general class of reamers, can remove only very small quantities of metal, so that they do not last as long.
Tapered Reamer
With conical tapered shape and angle. Tapered reamers are employed for giving a slight taper to predrilled cylindrical holes.
The taper is usually required to fit a tapered pin for locating purposes or a tapered shaft, as is used on one end of all Morse tapers, the standard taper for tooling.
Drill Reamer
Also, a reaming drill, enables one to drill and ream in the same operation, saving time. Of course, a reaming drill is only suitable for through holes.
If the holes are to be accurately located, however, a drilling operation with a separate reaming operation is better.
Alignment Reamer
Essentially a heavy reaming tool, alignment reamers form an important reamer used in the industry to check the accuracy of holes. Reamers increase the size, as well as keep the hole straight and parallel, a necessary condition for many mechanical components to operate correctly.
Because of the fine quality of work turned out with the alignment reamer, this tool finds a wide application in the swap industry on machinery and equipment as the slightest inaccuracy at any point would result in lengthy and expensive rework.
Through the use of the alignment reamer, machinists are assured of turning out the correct size work.
Types of Reamer
The following are the main types of reamer tools:
- Chucking reamer with parallel or taper shank
- Fluted reamer
- Rose reamer
- Machine bridge reamer
- Machine jig reamer
- Parallel hand reamer with a parallel shank
- Parallel or taper shank socket head reamer
- Shell reamer
- Taper pin hand or machine reamer
- Expansion reamer
#1. Chucking Reamer with Taper or Parallel Shank (Fluted).
It is also called a machine reamer. These types of reamer available consist of short parallel cutting edges with bevel lead and long body recess between shank.
Cutting edges integrated with a parallel or taper shank for holding the reamer. The flutes are all straight, but the shank may be straight or taper.
The reamer is designed to be used in a drill press, turret lathe, or screw-cutting machine. It is driven at slow speed and the entire cutting is done along with the flutes. The flutes are spaced irregularly around the circumference of the body of the reamer.
This decreases the tendency to chatter. The fluted reamer is used for reaming more accurate work. The diameter of a straight shank chucking reamer ranges from 1-5 to 32 mm and for a taper shank from 5 to 32 mm.
#2. Chucking Reamer (Rose).
It differs from the fluted type in that the cutting is all done by the beveled edges at the end. The angle of the chamfered cutting edges is 45°. The fluted body fits into the reamed hole.
The body is slightly tapered, being small towards the shank to prevent bending in the hole. A greater amount of metal can be taken off with this type of reamer than with a fluted type. A chucking rose reamer.
#3. Machine Bridge Reamer.
A machine bridge reamer illustrated used as a portable electric or pneumatic tool for reaming in ship-building, structural, and plate work.
These types of reamers have parallel cutting edges, and a long lead; the whole is integral with a tapered shank for holding and driving the reamer. The flutes may be straight or helical. The diameter of the reamer varies from ¼ inch to 1 ½ inch.
#4. Machine Jig Reamer.
A machine jig reamer consists of short parallel cutting edges with bevel lead and a guide between the shank and cutting edges, all integral with a tapered shank for holding and driving.
The flutes are helical. The plain part of the body fits into a bushing in the jig to accurately locate the reamer. The diameter of the reamer varies from ¼ inch to 2 inches. The reamer is illustrated.
#5. Parallel Hand Reamer with Parallel Shank.
This reamer consists of parallel cutting edges with taper and bevel lead not separable from a shank of the nominal diameter of the cutting edges, and with a square on the end.
The flutes may be either straight or helical. The hand reamer has a square tang and is adapted to be hand-driven for the purpose of accurately sizing the holes.
The reamers are supposed to remove the least amount of metal, from 0·05 to 0,125 mm. It is slightly tapered towards the end for a distance equal to the diameter for easy starting. This kind of reamer.
#6. Socket Reamer, Morse Taper.
This reamer may either be straight or taper shank type and may also be hand or machine-driven. The reamers have taper cutting edges to fit Morse taper, not separable from a parallel or taper shank. The flutes may be straight or helical.
The reamer tools are obtainable in a set of three: roughing, pre-finishing and finishing. The diameter of the reamers is supplied for the finishing. Morse taper holes from No. 1 to 6. A socket reamer.
#7. Shell Reamer.
A shell reamer, as shown in the figure, has an axial hole for use on an arbor, and has practically parallel cutting edges with a sharpened bevel lead.
These kinds of reamer tools are used for finishing large holes to save the tool more than one hundred or more sizes of shells. The various sizes of such shell reamer fits over one arbor. This system saves the cost of the solid shank in every case.
The shell reamer may, therefore, either be the rose chucking system for truing the hole or the fluted type for finishing. The flutes may also be either straight or helical. The diameter of the reamer varies from 024 to 100 mm.
#8. Taper Pin Reamer.
The reamer tool, as shown in the figure, may be hand or machine that is, is driven. This has taper cutting edges for holes to suit pins having a taper of 1 in 50, with a parallel or taper shank for holding and driving the reamer. The flutes may also be straight or helical.
#9. Expansion Reamer.
An expansion reamer is so constructed that it can be adjusted by a very small amount to compensate for wear, or to accommodate some variation in hole size.
As shown in the figure to effect the expansion, the clamping nut is loosened and plug is pushed inward, thus effecting the expansion of the blades by a small amount.
Applications of Reamer
The applications of a reamer are:
- A reamer is a rotary cutting tool mostly used in metalworking.
- A reamer is a tool for enlarging or finishing holes previously drilled, bored, or cored to a fine finish and a correct size.
- Reamer tool is intended for use in a drill press, or on a turret lathe.
- Reamer is also used in the screw-cutting machine.