What is Reamer? – Construction, and Types

What is Reamer?

A reamer is a type of rotary cutting tool of cylindrical or conical shape used for enlarging and finishing to accurate dimensions holes that have been drilled, bored, or cored. A reamer cannot be used to originate a hole. Machine reamers are used on machine tools such as drill presses, lathes, and screw machines.

Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers that are used for more basic enlargement of holes or for removing burrs.

The process of enlarging the hole is called reaming. There are many different types of reamers and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press.

Construction

A typical reamer consists of a set of parallel straight or helical cutting edges along the length of a cylindrical body. Each cutting edge is ground at a slight angle and with a slight undercut below the cutting edge.

Reamers must combine both hardness in the cutting edges, for long life, and toughness, so that the tool does not fail under the normal forces of use. They should only be used to remove small amounts of material. This ensures a long life for the reamer and a superior finish to the hole.

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The spiral may be clockwise or counter-clockwise depending on usage. For example, a tapered hand reamer with a clockwise spiral will tend to self-feed as it is used, possibly leading to a wedging action and consequent breakage. A counter-clockwise spiral is therefore preferred even though the reamer is still turned in the clockwise direction.

For production machine tools, the shank type is usually one of the following: a standard taper (such as Morse or Brown & Sharpe), a straight round shank to be held by a collet, or a straight round shank with a flat for a set screw, to be held by a solid tool holder. For hand tools, the shank end is usually a square drive, intended for use with the same type of wrench used to turn a tap for the cutting of screw threads.

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Types Of Reamers

The following are the main types of reamer tools:

  • Chucking Reamer.
  • Adjustable hand reamer.
  • Straight reamer.
  • Rose reamer.
  • Shell reamer.
  • Tapered reamer
  • Combination reamer.
  • Tapered reamer (non-precision)

1. Chucking Reamer

Chucking reamers, or machine reamers, are the most common type of reamer used in lathes, drill presses, and screw machines that provide a smooth finish to the hole. They come in a variety of flutes and cuts (e.g., right-hand cut, left-hand spiral, straight flute) as well as different shank types. Chucking reamers can be manufactured with a straight shank or morse taper shank.

2. Adjustable hand reamer

An adjustable hand reamer can cover a small range of sizes. They are generally referenced by a letter that equates to a size range. The disposable blades slide along a tapered groove. The act of tightening and loosening the restraining nuts at each end varies the size that may be cut.

The absence of any spiral in the flutes restricts them to light usage (minimal material removal per setting) as they have a tendency to chatter.

They are also restricted to usage in unbroken holes. If a hole has an axial split along with it, such as a split bush or a clamping hole, each straight tooth will in turn drop into the gap causing the other teeth to retract from their cutting position. This also gives rise to chatter marks and defeats the purpose of using the reamer to size a hole.

3. Straight reamer

A straight reamer is used to make only a minor enlargement to a hole. The entry end of the reamer will have a slight taper, the length of which will depend on its type. This produces a self-centering action as it enters the raw hole. The larger proportion of the length will be of a constant diameter.

4. 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. It also allows the reamer to start straight and reduce the risk of breakage. The flutes may be straight or spiral.

5. Machine reamer

A machine reamer only has a very slight lead-in. Because the reamer and workpiece are pre-aligned by the machine there is no risk of it wandering off course. In addition, the constant cutting force that can be applied by the machine ensures that it starts cutting immediately.

Spiral flutes have the advantage of clearing the swarf automatically but are also available with straight flutes as the amount of swarf generated during a reaming operation should be very small.

Types Of Reamers

6. Rose reamer

A rose reamer has no relief on the periphery and is offset by a front taper to prevent binding. They are secondarily used as softening reamers.

7. Shell reamer

Shell reamers are designed for reaming bearing and other similar items. They have fluted almost their whole length.

8. Tapered reamer

A precision tapered reamer is used to make a tapered hole to later receive a tapered pin. A taper pin is a self-tightening device due to the shallow angle of the taper. They may be driven into the tapered hole such that removal can only be done with a hammer and punch. They are sized by a number sequence (for example, a No.4 reamer would use No.4 taper pins).

Such precision joints are used in aircraft assembly and are frequently used to join the two or more wing sections used in a sailplane. These may be re-reamed one or more times during the aircraft’s useful life, with an appropriately oversized pin replacing the previous pin.

9. Morse taper reamer

A morse taper reamer is used manually to finish morse taper sleeves. These sleeves are a tool used to hold machine cutting tools or holders in the spindles of machines such as a drill or milling machine. The reamer shown is a finishing reamer. A roughing reamer would have serrations along the flutes to break up the thicker chips produced by the heavier cutting action used for it.

10. Combination reamer

A combination reamer has two or more cutting surfaces. The combination reamer is precision ground into a pattern that resembles the part’s multiple internal diameters. The advantage of using a combination reamer is to reduce the number of turret operations, while more precisely holding depths, internal diameters, and concentricity.

Combination reamers are mostly used in screw machines or second-operation lathes, not with Computer Numerical Control (CNC) machines because G-code can be easily generated to profile internal diameters.

11. Tapered reamer (non-precision)

A tapered reamer may be used for cleaning burrs from a drilled hole, or to enlarge a hole. The body of the tool tapers to a point. This type of reamer consists of a body that, typically, is up to 1/2 inch in diameter, with a rod cross piece at the large end acting to form a handle.

It is especially useful for working softer metals such as aluminum, copper, and mild steel. Another name for it is “maintenance reamer”, referring to its use in the miscellaneous deburring and enlarging tasks often found in MRO work. A similar tool can be seen on select Swiss Army knives, such as the electrician model, to be used on the conduit.

Applications of Reamer

The following are the applications of reamer:

  • A reamer is a type of rotary cutting tool mostly used in metalworking.
  • A reamer is a tool used for expanding or finishing pre-drilled holes, bored, or cored to give a good finish and an exact dimension.
  • The reamer is intended to be used in a drill press, turret lathe.
  • Reamer is also used in the screw-cutting machine.