SU903077A1 - Method of determining maximum permissible wear of drill - Google Patents

Description

(54) METHOD FOR DETERMINING THE ULTIMATE ALLOWABLE

WEAR DRILL

one

The invention relates to the establishment of criteria for blunting a cutting tool, such as a drill, for the purpose of replacing a tool before the onset of catastrophic wear, and can be used in testing tools of a new design.

There is a known method for determining the maximum allowable wear of a drill, which includes measuring the linear wear values of the most wear drill elements with their subsequent summation and comparing the values obtained with the maximum allowable wear of the reference drill 1.

The disadvantage of this method is that linear wear is measured directly during the forced intermediate withdrawal of the tool from the cutting zone. At the same time, a large volume of metal is drilled and a considerable amount of time is spent measuring wear. The accuracy of the method is reduced due to the variation of the experimental data due to the inconstant hardness of the metal blanks, errors in sharpening and manufacturing of the drill.

The purpose of the invention is to reduce the complexity of the method and improve the accuracy of determining the maximum allowable wear.

The goal is achieved by measuring the torsional moments when drilling with a reference new drill and at the maximum permissible wear, torsional rigidity and breaking torque for the reference drill, and for the tested new drill torsional stiffness and torsion, with Thereby, the maximum permissible wear is determined by the formula

h h de re-KmMe

  ..

g.E.

WZ MRE- / L

15

where Vi is the maximum allowable wear of the test drill, mm;

hj3 is the maximum allowable wear of the reference drill, mm;

Ma - the drilling torque

20 new standard drill, kgf-m;

MRD-destructive torque of the reference drill, kgf m

K is the ratio of the torque at the maximum allowable wear of the reference drill to its destructive torque; K, 4 is the ratio of torques when drilling with new test and reference drills; the ratio of the torsional stiffness of the test and reference drills.

FIG. 1 shows an apparatus for measuring drill wear; in fig. 2 - a view of the drill from the side of the cutting part and a diagram of the wear of the drill elements with linear wear values.

Drill 1 is fixed on the drilling machine 2 and is located inside the pulley 3, which is connected by a cable 4 thrown over the block 5 to a spring dynamometer 6. Pulley 3 contains screws 7, which can be inserted into the chip grooves 8 of the drill 1 when screwing in 8. Preparation 9 mounted on an electric dynamometer 10 mounted on the table 11 of the sverililny machine 2. A variable force R is applied to the spring sensor 6.

The proposed method is implemented as follows.

On the drilling machine 2, the reference drill 1 is fixed and the workpiece 9 is drilled, for example, from a hard-to-machine material. Immediately after cutting the drill 1 in - workpiece 9; until the drill is blunt, the torque L1e is measured using an electric dynamometer 10, continue to be drilled until signs of allowable wear of the drill 1 occurring in an increase in the vibrations of the drill 1, appear. accompanied by the creaking and cracking, after which the torque is measured again.

On the drill 1, the most wearable elements are measured, for example, the back surfaces 12, the corners 13, the transverse blade 14, and the linear wear, respectively hj, bn, which sum up, determine the maximum allowable wear of the reference drill hj + h × hp. Screws 7 are then inserted into the chip grooves 8 of the drill 1, a force P equal to 2M / D is applied to the spring dynamometer 6 and the angle of rotation of the pulley 3 that corresponds to the unwinding angle Te of the drill 1 is measured. Calculate the torsional rigidity of the reference drill j The force P is increased to the value of Pp at which drill 1 is destroyed, the breaking torque Mre of the reference drill 1 is calculated as Mp -PpD / 2. A drill 1 of the tested construction is installed on a drilling machine 2 and the workpiece 9 is drilled. Immediately after cutting, until drill 1 does not become blunt, the torque is measured using an electric dynamometer 10 when drilling M

Screws 7 are introduced into the chip grooves 8 of the drill 1, a force P equal to 2 Me / D is applied to the spring dynamometer (according to the test of the reference drill), and the angle of rotation of the pulley 3 is measured, corresponding to the unwinding angle n of the test drill 1. torsional rigidity of the test drill 1 as Jn Me. Calculate the ratios of: torque at the maximum allowable wear of the reference drill L1pe to its breaking torque L1pe / Afp ;; torques when new subjects test M and reference L drills (Cj, Mn / M), torsional rigidity of the test and reference jg drills In a 5-Paul test, as a result of the operations performed, the values are substituted into the calculation formula and the desired maximum allowable wear of the test drill

h h Mre-Km Mae

I 11

Kde re me

The reference drill is tested once and the data obtained are used to determine the maximum allowable wear of various drills of the structure under test. In this case, the tests consist in the fact that for the tested drill only the torque is measured when drilling with a new drill and torsional rigidity. Accordingly, the amount of testing, the complexity of the method is significantly less than with known methods.

The accuracy of the proposed method is high due to the lack of cost tests for test drills, which always give a large scatter of experimental data. At the same time, torque measurement during drilling and torsional rigidity can be performed with high accuracy.

Thus, the proposed method for determining the maximum allowable wear of the drill has less labor and increases the accuracy of determination.

Claims (1)

Invention Formula A method for determining the maximum allowable wear of a drill, which includes measuring the linear wear values of the most wear drill elements and then summing them up and comparing the received values with the maximum allowable wear of a reference drill, characterized in that, in order to reduce labor intensity and increase the accuracy of determinations, torsion points when drilling with this new drill and with the maximum allowable wear, torsional rigidity and breaking torque for the reference drill, and for testing direct new