Many people puzzle over the difference between boring and drilling: they both involve cutting holes in a workpiece, right? If you look in a dictionary, you will probably see the same definition for both; however, to a machinist or manufacturing engineer, there is a very specific between the two despite the fact that many people use the terms interchangeably. In this article, we are going to look the major difference between the two, then see how the tooling, processes, and end results differ.
Drilling is a process for removing material from a workpiece in order to create a hole. Boring, on the other hand, is a process of enlarging a hole that has already been made by another process (such as drilling or casting). In short, boring is a secondary finishing operation.
Drilling requires a cutting tool called a drill bit. The drill bit is rotated and forced into the surface of the material, removing metal in the form of chips and producing a round cavity in the process. Drilling is concerned with both the diameter of the hole and the depth of the hole. It can be done on a milling machine, lathe, or machining center, but there are also machines designed specifically for drilling called drill presses. Deep hole drilling, however, is a very specific kind of drilling process for holes that have a high ratio of depth to diameter. Deep hole drilling requires specialized equipment and involves a different manufacturing process.
A straight hole is drilled with a specific diameter and depth. Depending on the tolerances and surface finish required, it may need to be followed up with a boring process.
As we already discussed, boring is a secondary finishing operation. The boring process is significantly different from the drilling process. Boring is accomplished using a heavy, stiff boring bar that has a single-point cutting tool at the end. This manufacturing process gives the machinist much more control of the diameter of the hole, allowing for a much tighter tolerance for diameter to be achieved. The goal of boring is to enlarge an existing hole, create a tapered hole from an existing hole, or achieve a desired surface finish inside an existing hole. Boring can be done on lathes, milling machines, or machining centers. There are also specialized machines for boring, such as boring mills or jig borers.
Suppose you need a hole with a diameter of 5 mm ± .2 mm. The best you can achieve with your drill press is 5 mm ± .5 mm. In that case, you would probably need to drill the hole slightly smaller than it needs to be, then use the boring process to achieve the tighter tolerance of ± .2 mm.
So, in short, boring is a secondary operation used to enlarge or taper an existing straight hole while drilling is the process used to create straight holes. If you need to make a hole in a solid piece of metal, you need to drill.