In order to create a hole on a solid surface, a series of different machining processes are carried out depending on the finish and tolerance level requirement. One typical series for hole making can be—(i) Centering, (ii) Drilling, (iii) Boring, (iv) Reaming, and (v) Honing.
These steps should be carried in exact sequence; one cannot be carried out prior to another. However, one or many steps may not be carried out if the quality requirement is not so strict. So skipping is allowed but rearranging is not allowed. Now, drilling is a process that originates a hole; while, boring enlarges the hole diameter. Reaming and honing are used to smoothen hole surfaces. Similarities and differences between drilling, boring and reaming are discussed in following sections.
Similarities between drilling, boring and reaming
- Drilling, boring and reaming—all are machining or metal cutting operations. So excess material is gradually removed from workpiece.
- All follow subtractive manufacturing philosophy (top-down approach).
- All of them are associated with hole fabrication.
- Chips are produced in all the processes.
- Cutter is used in all three cases.
Differences between drilling, boring and reaming
Purpose of operation
- Drilling is carried out to originate a cylindrical hole. So it can create a hole on a solid surface.
- Boring is performed to enlarge an existing hole or to make a taper hole from a cylindrical hole.
- Reaming is carried out to highly finish the surfaces of a hole. It can be carried out after drilling or reaming.
- Drilling does not require any special feature for it. However, centering can be done prior to drilling to improve accuracy.
- Boring requires an existing hole for its operation. Such holes can be made either by drilling or by casting.
- Reaming also requires a cylindrical hole for its operation. Also hole diameter should match with reamer diameter.
Cutting tool used
- Drilling uses a double point cutting tool called drill. So it has only two cutting edges that simultaneously participate in cutting action.
- Boring uses a single point cutting tool called boring bar. The tool is similar to turning tool (SPTT) operation is similar to internal turning.
- Reaming uses a multi-point cutting tool called reamer.
Capability to alter diameter and length of hole
- In drilling, diameter of hole depends on and thus limited to selected drill diameter. However, length of hole can be varied during operation.
- Boring is performed to increase diameter of an existing hole. It can also make a taper hole from a cylindrical one. However, it cannot increase length of the hole.
- Reaming is basically finishing process that can increase hole diameter by a small amount. Length cannot be altered by reaming.
Quality of surfaces of hole
- Drilling does not provide a highly finished surface.
- Boring can provide comparatively better surface.
- Reaming is performed to obtain a highly finished surface. So it provides best surface finish and accuracy among these three processes.
Possibility of making taper hole
- Taper holes cannot be fabricated by only drilling.
- After drilling a cylindrical hole, boring can be utilized to make a taper hole.
- Reaming can be utilized for smoothening surfaces of a taper hole.
Material removal rate (MRR)
- Drilling undoubtedly provides high MRR. So it is suitable for stock removal.
- Boring also provides high MRR; however, lower than drilling.
- Reaming gives poor MRR; in fact, MRR is not an objective for carrying out reaming. Its purpose is to obtain highly finished surface.