31-07-2012, 11:49 AM
Tool Design MEC445 Fixture
13157_BoringFixture.ppt (Size: 8.28 MB / Downloads: 474)
Boring achieves three things:
Sizing: Boring brings the hole to the proper size and finish. A drill or reamer can only be used if the desired size is "standard" or if special tools are ground. The boring tool can work to any diameter and it will give the required finish by adjusting speed, feed and nose radius. Precision holes can be bored using microadjustable boring bars.
Straightness: Boring will straighten the original drilled or cast hole. Drills, especially the longer ones, may wander off-center and cut at a slight angle because of eccentric forces on the drill, occasional hard spots in the material, or uneven sharpening of the drill. Cored holes in castings are almost never completely straight. The boring tool being moved straight along the ways with the carriage feed will correct these errors.
Concentricity: Boring will make the hole concentric with the outside diameter within the limits of the accuracy of the chuck or holding device. For best concentricity, the turning of the outside diameter and the boring of the inside diameter is done in one set-up-that is, without moving the work between operations.
Boring Fixtures
Boring Fixture may have the characteristics of a drill jig or a mill fixture, depending on the type of boring
Boring is usually accomplished with a size point tool, and the size of the hole depends upon the adjustment of the tool within the boring bar.
Machines used for boring operations are drill presses with power feed, milling machines, lathes, jig boring machines, vertical and horizontal boring mills, and special purpose boring machines operated manually or automatically