Drill guide for linked parallel holes - has second bore cut with aid of guide bar and bush to avoid wandering

摘要

Long bores breaking into each other, are machined by cutting the second bore with the help of a guide bar and bush arrangement which follows the first bore. The alignment of the boring head is then not dependent upon the forces working on it whilst the second bore is being cut. The bores can be machines parallel without the deflection caused by differences in resistance to the cutters during their passage. In the first bore a comparatively short guide bar (4) has secured to it a sleeve (5) through which the boring bar (3) carrying the cutting head extends. Oil is fed directly to the cutters so that adequate lubrication is also available in recesses to give hydrostatic bearing protection against shock loading.