SU1682050A1 - Spiral drill - Google Patents

Abstract

The invention relates to metal cutting and can be used for drilling deep holes. The aim of the invention is to increase the resistance of the drill by increasing the strength of the additional guide strips. The drill bit contains teeth, which are separated from each other by means of screw chips with grooves, the front walls 3 of which are inclined to the drill axis by an angle about: more than 90 °, and the rear walls 4 are inclined in an opposite direction relative to the front walls. corner a on the front walls. On each wall of the teeth, there are main 6 and additional 7 guide ribbons of the same width, matched with the back of the tooth with one radius. 4 il.

Description

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The invention relates to metal cutting and can be used for drilling deep holes.

The aim of the invention is to increase the resistance of the drill by increasing the strength of the additional guide strips.

Fig, 1 shows the proposed drill, a general view; 2 is a section A-A in FIG. one; on fig.Z - section bb in fig. one; figure 4 - diagram of the forces acting on the particle chips (in section bB).

The drill bit contains teeth 1 and 2 (Fig. 1), which are separated from each other by means of screw chutes. The chip groove profile is formed by the front wall 3 (FIG. 2), located on the side of the drill tip, and the rear wall 4. The front wall is inclined to the drill axis at an angle a greater than 90 °, and the rear wall is inclined in the direction opposite to the front wall at angle / 3 not less than at angle a on the front wall.

On each backrest 5 (fig. 3) of the teeth there are two guiding ribbons: main 6, located from the front wall side, and additional 7, located from the rear wall side. The main and additional ribbons are made of the same width f and are matched with the back of a tooth with a radius of g. The width of the guiding ribbons f is selected depending on the diameter of the drill from the conditions for ensuring their strength and reducing friction against the hole walls. The magnitude of the radius r is chosen from the condition of ensuring the strength of the guide ribbons and the gap for the passage of the cooling fluid to the cutting zone.

Figure 4 shows a diagram of the forces acting on the particle of the shipment during its transportation along the helical groove of the drill. The greatest pressure of the chips on the rear wall occurs at the point O when the chips move from a curved surface to a straight section of the rear wall. The particle P at this point is affected by the force P pressing it to the rear wall, and the centrifugal force W arising when the chip rotates about the axis of the hole (the force of the particle of the chip and its radial component can be neglected due to their small size). The force P is directed normal to the surface of the rear wall 4 and makes an angle y with the drill axis. The force W is perpendicular to the axis of the drill and makes an angle y with the rear wall. Re E

The resultant force F P + W is an angle with the drill axis. The magnitude of this angle depends on the ratio of the forces P and W, i.e. on the magnitude of the angle p between the resultant

force F and its component R. With an increase in the angle, the load on the additional guide ribbon is increased, to unload this ribbon, it is necessary that the direction of the resultant force F be not higher than point A (according to the diagram) located in the middle of the back of the radius g.

This condition is met when the angle values are: / 3 90 ° + p - in, where in is the angle between the line OA and the axis of the drill. The outcome of this

Conditions and based on the analysis of the results of comparative resistance tests of prototypes of the proposed drills, an experimentally derived formula for the dependence of the back wall inclination angle / 3 on the inclination angle of the front wall a, drill diameter d and width of the guide strips f, is

25

sin (a-S) Pa + g-- d.

As can be seen from the equation, the inclination of the back wall can be less than the inclination angle of the front wall:

 with a 5 and / 3 a with a 5. .

The lower limit of the angle 3 is limited by the condition of chip transport, and the upper limit by the condition of ensuring the strength of the additional guide tape. It was established experimentally that the optimal angle value / 3 for drills with a diameter of 6 to 10 mm is within 95 °, 115 °.

Spiral drill works as follows.

During the drilling process, the coolant is fed into the cutting zone along the backs 5, which are coupled with a radius of r with the primary 6 and an additional 7 guide ribbons. Shear chips are transported along the helical grooves of the drill, while the chips create pressure on the front 3 and rear

And the walls of the grooves, the inclination of the front 3 and rear 4 walls of each channel, at angles ai fj greater than 90 ° with respect to the drill axis, improves the transportation of chips and simultaneously increases the strength of the main

Claims (1)

and additional guiding ribbons. Formula of an Isobenet A spiral drill containing screw chipping grooves, the front walls of which are made at an angle greater than 90 ° with the drill axis, four guide ribbons, two on the back of each tooth, while the main ribbon is located on the side of the front wall of the helical grooves and additional - from the rear wall, characterized in that, in order to increase the resistance of the drill by increasing the strength of the additional guide strips, the rear walls of the screw grooves are inclined to the axis of the drill in the direction oppositely relative to the front wall direction of the angle defined by the equation 6 h sin (a-5) in a + p- - d, where the angle of inclination, respectively, of the front and rear walls of the helical grooves to the drill axis, degrees; d is the outer diameter of the drill, mm f is the width of the guiding ribbons, mm. and the main and additional guide ribbons are made of the same width and are matched with the back of the tooth with one radius. Fig.Z FIG. four