SU1349914A1 - Threading tap - Google Patents

Abstract

The invention relates to metalworking and can be used when tapping threads. The purpose of the invention is to improve the accuracy of the thread being cut and the durability of the tap by reducing the torque when cutting threads in short through holes. The tap includes a calibrating part and a cutting part, which is made in the form of conical sections with guide and cutting parts. The angle of inclination of the conic sections and their number are determined from mathematical relationships. While the cutting part of the first conic section cuts, the guide part of the second conical section enters the cutting hole. 2 Il. with .4 CO CD

Description

The invention relates to metalworking and can be used when tapping threads.

The purpose of the invention is to improve the accuracy of the thread being cut and the durability of the tap by reducing the torque when cutting threads in short through holes.

FIG. 1 shows a tap, general view; in fig. 2 - the same, increased profile of the cutting part.

The tap includes the calibrating part 1 and the cutting part 2, which is made in the form of conical sections with the clamp S and the angle of inclination. Each of the conic sections contains a guide part, liii, 1 "2, 1" h, respectively, and a cutting part, respectively, 1p1, lj, 2, 1rz, formed by one and a half to two turns of thread.

Here, do is the largest diameter of the guide part of the first conical section, di is the largest diameter of the cutting part of the first conical section, d2 is the largest diameter of the cutting part of the second conical section, d is the largest diameter of the third conical section and the outer diameter of the calibrating part of the tap.

The number of cones is derived from the following mathematical relationship

Fri k a-k-z

and the angle of inclination of these conic sections is determined by the subformula

F arctgg--

 PF k p

e estimated number of conical

plots; H - the height of the active section of the profile

tap threads; and - the magnitude of the rise per tooth; k is the number of threads on the cutting part of each conical section;

Z is the number of feathers of the tap; f-angle of inclination of the conical sections; PF-accepted quantity of conic

plots; p - tap thread pitch.

fieL

Tap works as follows.

At first, the guide part of the first conical section enters the hole, and the cutting part of the last part begins to cut after it. While the cutting part of the first conic section is cut, the n-guide part of the second conical section enters the cutting hole, and at that moment when the cutting part of the first conical section finishes cutting, the cutting part of the second conical section and so on comes into operation. d.

Thus, cutting parts of all conic sections of the tap are involved in cutting. Therefore, the torque that occurs when cutting the cutting part of one conical section is not superimposed on the torque that occurs when cutting the cutting part of the next conical section.

20

Claims (1)

Invention Formula five 0 A tap comprising calibrating and cutting parts made along a helical line, characterized in that, in order to increase the thread cutting accuracy and reduce the torque, the cutting part is made in the form of consecutively arranged conical sections, each of which includes successively arranged guide and the cutting part 0, the latter containing 1.5-2 turns, and the number of conic sections and their angle of inclination are determined from the following mathematical relationship: H a k Z F arctg -1- wheredept is the estimated number of conical plots; H - the height of the active section of the profile five five tap threads; and - the magnitude of the rise per tooth; k is the number of threads on the cutting part of each cone section; Z is the number of feathers of the tap; f-angle of inclination of the conical section; pf-accepted number of conic sections; p - thread pitch. ji.2