Boring is a machining process that involves enlarging an already drilled hole. This is done by means of either a single point cutting tool or boring heads containing several such tools. Boring is used to achieve greater accuracy of the diameter of a hole and can be used to cut a tapered hole. Boring tools can provide adjustment precision as fine as .0001 inches. There is a large variety of sizes and styles of boring machines. Boring operations on small work pieces can be performed on a lathe, while larger work pieces are machined on boring mills. Here is some basic information on the variations of boring tools, machines and techniques.
- Horizontal Machines
- Vertical Machines
In lineboring, the boring bar may be supported on both ends but only if the existing hole is a through hole. A through hole is one that extends all the way through the piece of machinery.
Backboring is the process of reaching through an existing hole and then boring on the back side of the work piece, relative to the machine headstock.
A horizontal boring machine is any that bores holes in a horizontal direction. The work piece sits on a table while the boring bar rotates around a horizontal axis. There are also three types of horizontal machines, table, planner and floor. The table is the most common and practical type, and is therefore known as the universal type.
Vertical boring machines that bore holes in a vertical direction. These machines rotate the work piece around a vertical axis while the boring head moves linearly.
Lathe boring is for small pieces and use a single point cutting tool or boring head to produce conical or cylindrical surfaces by enlarging an existing opening in a work piece.
The limitations in geometric accuracy and hardness of the finished product from boring continue to diminish as technology progresses. Higher grade boring inserts have increased the accuracy that can be achieved without grinding, and have increased the range of work piece hardness values that are workable. This is excellent news for a field that deals in such minute measurements. For instance, surface finish, or roughness, may range from 8 to 250 microinches, but is typically between 32 and 125 microinches. Higher quality boring tools allow for more precise pieces and better finished pieces. Top quality tools can make the difference of only a few microinches, but in boring technology, that is all a huge difference.