Background technology
The shape of its drilling end of fluted drill of the prior art mostly is the structure as Fig. 1, protrude a sharp-pointed apex point 01 in the middle of it, outwards extend two conical surfaces symmetrically by apex point 01, itself and two spiral grooves have formed two end swords 02 and 03, in end sword 02 and 03 back relative with spiral grooves 04, be provided with nextly 05, make the end sword sharper.There are some defectives in this drill bit when the parts of some material of drilling and some shape: for example, above-mentioned drill bit is in processing rigid timber and sheet metal, because the end sword is sharp like that for being not so good as apex point, the hole that gets out, its inwall is rough, even burr occurs, has influenced crudy.
Summary of the invention
The purpose of this utility model is to improve deficiency of the prior art, provide a kind of when processing rigid timber or sheet metal the hole inner wall smooth, do not have the Short drill with three-tip of burr.
The purpose of this utility model is achieved in that
The drilling end of the Short drill with three-tip that the utility model provides, protrude a sharp-pointed apex point in the middle of it, outwards extend two steep inclined-planes downwards symmetrically by described apex point, this inclined-plane make progress again a side of apex point (promptly to) tilt to extend one section excircle to drill bit, the described steep downward inclined-plane and the groove bottom of acclivitous again inclined-plane and existing two spiral grooves form two sections end swords, the groove bottom of described steep inclined-plane and spiral grooves has formed the sharper front edge of middle apex point, the groove bottom of acclivitous again inclined-plane and spiral grooves has formed the end sword of both sides indents, the outer circumference surface of this end sword and fluted drill has formed two outside points, constitutes the drilling end of tricuspid shape with the apex point of centre; In the end sword of described two indents back relative with spiral grooves, as existing fluted drill, be provided with the back, make the end sword sharper.
The Short drill with three-tip that the utility model provides, by the end sword structure different with fluted drill in the prior art, on the excircle of drill bit, form two apex points again, in boring, can process the hole of inner wall smooth, when the processing metal thin plate, can be to the residual drilling cuttings in limit, hole, because end sword indent, the end sword becomes sharper, the aperture, edge up and down in the hole of processing can be not crude yet, and the problem of burr will be resolved.
Angle between the conical surface that the angle between described two steep inclined-planes outwards extends more than existing fluted drill apex point is little, is generally 5-15 °.This angle is more little, and middle apex point will be thin more, and is sharp-pointed more, and apex point is long more in the middle of also can making.But if angle is too small, the intensity of middle apex point will reduce, if this angle is excessive, then middle apex point can be too short, and the tricuspid structure of formation is not obvious, and it is not obvious that its good effect also can become.
The angle of described two acclivitous again inclined-planes and horizontal plane generally can be at 1-10 °.The size of this angle determines the length of two outside apex points.This angle is too small, and apex point is not obvious, and effect is not outstanding, but this angle can not be excessive, otherwise the intensity of outside apex point also can slacken.
The Short drill with three-tip end sword indent that the utility model provides, two apex points in the outside can give better cutting to the inwall in hole of processing, therefore, especially when processing rigid timber or sheet metal, the hole inner wall smooth, do not have burr.
The specific embodiment
As shown in Figure 2, the drilling end of the Short drill with three-tip 1 that the utility model provides, protrude a sharp-pointed apex point 2 in the middle of it, outwards extend two steep inclined-planes 3 downwards symmetrically by apex point 2, this inclined-plane 3 make progress again a side of apex point (promptly to) tilt to extend the excircle of one section inclined-plane 4 to drill bit, the steep downward inclined-plane 3 and the groove bottom of acclivitous again inclined-plane 4 and two spiral grooves 5 form two sections end swords 6, the steep inclined-plane and the groove bottom of spiral grooves have formed the sharper front edge of middle apex point, the groove bottom of acclivitous again inclined-plane and spiral grooves has formed the end sword of both sides indents, the outer circumference surface of this end sword and fluted drill has formed two outside points 7, constitutes the drilling end of tricuspid shape with the apex point 2 of centre; In the end sword of two indents back relative with spiral grooves, as existing fluted drill, be provided with the back (not shown), make the end sword sharper.
Angle between two steep inclined-planes 3 is 5 °.Two acclivitous again inclined-planes 4 generally can be at 8 ° with the angle of horizontal plane.Connect by the camber line transition between inclined-plane 3 and the inclined-plane 4.