WO2003064094A1

WO2003064094A1 - Screwing tap with multiple working head

Info

Publication number: WO2003064094A1
Application number: PCT/HU2002/000174
Authority: WO
Inventors: László VILMÁNYI
Original assignee: Vilmanyi Laszlo
Priority date: 2002-01-30
Filing date: 2002-12-28
Publication date: 2003-08-07
Also published as: HU0200339D0; HUP0200339A2

Abstract

The invention discloses a new screwing tap (1) having a special structure. The tap (1) has at least two uniform working heads (A1, A2, A3) arranged spaced apart along the length of a tool shaft (Z).

Description

Screwing tap with multiple working head

Technical field

The invention relates to a screwing tap having a first portion provided with working head with cutting wings, and a second portion formed as a tool shaft being to be bitten by a die chuck. Background art

It is widely known, that the screwing tap is a cutting tool most frequently used to prepare threads into bore-holes. The conventional screwing tap can be divided into two portions. A working head provided with entering and controlling portions is situated in the first end of a screwing tap. The second end opposite to the first end of the tool is formed as a shank having cylindrical shape being able to be bitten by a die chuck or toolholder. The working head is provided by at least two cutting wings and grooves for chips (or flutes) arranged therebetween along at least the full length of said wings.

The screwing taps according to the state of the art may be classified in accordance with their thread type, base material, use and way of production. With exception of different thread types, the screwing taps have the following three types: set of brace taps, machine tap and long-shaft taper tap. With regard to their flutes the screwing taps might be produced with different designs. The base materials generally used for the screwing taps are the shear-steel (WS), R6 high-speed steel (HSS), and the high-speed steel containing 5 wt% of cobalt (HSS-E).

Generally, the screwing taps having a maximum diameter of 12 mm are made of WS or HSS/HSS-E material. In order to decrease the production costs the shaft of a screwing tap having a diameter above 12 mm is made of carbon steel causing lower costs. The use of screwing taps having a cooling passage and produced by a powder metallurgical method is getting known better and better. In order to increase the operating lifetime the working head of the screwing taps is provided with different coatings (TiN, TiCN).

In a common way, the length of the working head of a screwing tap is only a third of the full length of the tool. The use of better base materials and coatings applied thereon confirms that there is an effort at the tool producers side to produce screwing taps being able to prepare more and more threads with a single tool.

Cutting operation using a screwing tap may be achieved by hand or by a cutting machine. Brace taps are available in sets, since this cutting operation consists of several different stages (pre-cutting, re-threading and finishing).

The machine screwing taps are formed as finishing tools with different (long or medium or short) entering edge lengths.

The entering portion of a screwing tap functions as to cut the workpiece material. The threaded controlling portion following the entering portion of a tool functions as to control threads cut and to guide the entire tool.

Wearing, fractures and even hacks must be occurred on the screwing tap during loading. These damages occur chiefly on the entering portion of the tool. In the case of an insignificant damage the screwing tap can be re-edged easily. On the contrary, the tool must be changed if above damage is so high, that it degrades essentially the cutting features of the tool.

With screwing taps according to the state of the art the cutting operation is achieved actually by means of % part of the entire tool length. In the case of a short cutting length not exceeding the diameter of the tool, the length of above part achieving cutting operation does not exceed 1/6 part of entire length of the tool. These are unfavourably bad operating rates resulting in a large quantity of waste material and increased production costs.

Therefore, it is a need in the art to create a screwing tap having longer lifetime and an operating rate better than above rates, and to create a screwing tap being able to prepare much more threads than a conventional tap and not increase or even lower production costs, and to diminish also the quantity of waste material arising at the plants using screwing taps. Description of the invention

With the screwing tap with multiple working head according to the invention, the number of threads possibly prepared by a single screwing tap can be increased significantly and even so the production costs of a screwing tap do not increase.

The screwing tap according to the invention has a first portion provided with working head having cutting wings, and a second portion formed as a tool shaft being to be bitten by a die chuck, and further, the first portion is provided with at least two or more working heads arranged sequentially along the length of the first portion. The sequentially arranged working heads preferably have identical thread profile, and an interspace located therebetween. The sequentially arranged working heads further have coarse cutting threads and finishing threads formed thereon.

The diameter of the interspace located between sequentially arranged working heads is preferably less than the diameter of an actual core boring, and the length of the interspace located between sequentially arranged working heads is preferably at most 5 times longer, than the actual pitch (p) of the working head.

The interspace located between sequentially arranged working heads is advantageously provided with a groove arranged circumferentially.

The invention will be presented in the fullest detail in accordance of attached drawings. Description of the drawings

Figure 1. is a side elevation view of a screwing tap according to the invention showing the working heads formed sequentially in a tool,

Figure 2. is a side elevation view of a screwing tap according to the invention showing the working heads arranged spaced apart along the length of the tool with an interspace B therebetween, Figure 3. is a side elevation view of a screwing tap according to the invention showing the working heads arranged spaced apart along the length of the tool and groovings D formed in each interspace. Detailed description of the invention

Figure 1. shows a preferred embodiment of a screwing tap 1 with multiple working head A1 , A2, A3 according to the present invention. The screwing tap 1 has at least two, preferably three or more adequate working heads A1 , A2, A3 having a basic diameter d and arranged sequentially along a first portion L of a tool shaft Z. The working heads A1 , A2, A3 have advantageously the same basic diameter d, but it will be appreciated by a person skilled in the art, that the working heads may also have different basic diameters d in any embodiment. Each working head A1 , A2, A3 is provided with entering portion consisting of first or coarse cutting threads N and a controlling portion consisting of finishing threads S. The coarse cutting threads N of the screwing tap 1 function as to cut firstly the workpiece material. The finishing threads S following the coarse cutting threads N function as to control and finish threads and to guide the entire tool.

The tool shaft Z has an end portion L1 having cylindrical shape (round in cross section in a preferred embodiment for example) being able to be bitten by a die chuck or toolholder. However, the end portion L1 may have any other cross sectional shape, i.e. rectangular, elliptical etc., as it is desired or useful.

This first embodiment of the screwing tap 1 according to the present invention is to preferably be used with extremely deep blind holes having a depth of 2 x d, since there is no gap between the working heads A1 , A2, A3 following each other and therefore it is impossible with chips to be jammed in any space and/or surface during cutting operation. At the same time, the coarse cutting threads N formed on the following working head A1 , A2, A3 have a diameter less than the finishing threads S, and therefore, they decrease friction between the inner surface of the hole and the screwing tap 1.

It is clear, that during cutting operation the first working head A1 will cut firstly, and loading of the second working head A2 is less, if the latter will work at all, depending on the depth of the bore-hole i. e. on the length of the thread to be prepared. Therefore, when the first working head A1 will have been damaged the user will simply detach it from the screwing tap 1 by means of a cutting device applied between working head A1 and A2. Consequently, the screwing tap 1 will be ready again to work by the working head A2 . Figure 2. shows a second embodiment of the screwing tap 1 according to the present invention. In this embodiment the screwing tap 1 has also at least two, preferably three or more adequate working heads A1 , A2, A3 having a basic diameter d and arranged sequentially along a first portion L of a tool shaft Z. The difference relative to the first embodiment is that the working heads A1 , A2, A3 have an interspace B located therebetween. The interspace B has a length being preferably at most 5 times longer, than the actual pitch p of the working head A1 , A2, A3, and has a diameter C less than the diameter of the actual core boring. By this interspace B the working head A2, A3... remained on the screwing tap 1 and its coating may be preserved from damages, which can be occurred during detachment of the worn-out working head A1 , A2, since said detachment will be achieved by cutting through the material located at said interspace B.

Figure 3. shows a third embodiment of the screwing tap 1 according to the present invention, which is similar to above second embodiment with exception that a circumferential groove D is situated on the surface of the interspace B, reducing the diameter C of the screwing tap 1. This groove allows the material of the interspace B to be broken away intentionally only by a hammer or similar object.

Advantageously, the aggregate length of a working head A1 , A2, A3 and an interspace B is equal to the length of a thread being to be prepared. This arrangement is chiefly preferred with open-end hole threads, if the cutting length does not exceed 1 ,5 x d.

Use of working heads A1 , A2, A3 arranged sequentially along the length of a tool shaft Z is very simple. A working head A1 , A2, A3 worn-out during use must be cut (or detach or broken away) from the screwing tap 1. Then the following working head A2, A3 will be ready to work immediately by a performance of 100%. When the lastly remained working head A3 (or An if there are more, than three heads) can be edged in a same manner as it would be a screwing tap belonging to the state of the art.

Examples A thread of 15 mm length (depth) was prepared into a blind bore-hole situated in a workpiece by a screwing tap according to the state of the art having a diameter d of 8 mm. This operation could have been repeated with 1000 bore-holes, when the screwing tap damaged and disabled to work. Then above operation was repeated by a screwing tap 1 according to the invention having two working heads A1 , A2. After preparing 1000 threads the first working head A1 damaged. Cutting off the working head A1 , further 1000 threads could be prepared with the screwing tap 1 having a second working head A2.

A thread of 15 mm length was prepared into a blind bore-hole having a depth of 20 mm situated in a workpiece made of GG40 (DIN standard of cast material) by a screwing tap 1 with 4 working heads according to the invention and having a diameter d of 10 mm. 3 coarse cutting threads N and 3 finishing threads were formed in each working head. In this way each working head A1 , A2, A3, A 4 had a length of 36 mm. The total length of this screwing tap 1 was equal to the length of a conventional screwing tap having similar purpose. The conventional screwing tap disabled after preparing 1500 threads. With the screwing tap 1 according to the invention this number of threads prepared was 6050.

The production costs of a screwing tap 1 according to the invention are equal to the production costs of a conventional screwing tap. The operation of the latter example would have required more than 4 conventional screwing taps. This result confirms conclusively the economical disadvantage of using conventional screwing taps.

Therefore, principal advantages of screwing taps 1 according to the present invention are as follows:

- reduces base material needs, - reduces the quantity of waste material accrued from machining,

- reduces needs of energy used for production of tools,

- increases significantly the number of threads prepared by a single tap. According to a conservative valuation of the inventor the overall production costs of the screwing taps 1 according to the invention can be reduced to the half value relative to the production costs of conventional screwing taps. In addition, the fewer screwing taps, the lesser waste material.

Claims

1. Screwing tap having a first portion provided with working head having cutting wings, and a second portion formed as a tool shaft being to be bitten by a die chuck, characterised in that the first portion (L) is provided with at least two or more working heads (Al , A2, A3, A4) arranged sequentially along the length of the first portion (L).

2. Screwing tap according to claim 1., characterised in that the sequentially arranged working heads (A1 , A2, A3, A4) have identical thread profile.

3. Screwing tap according to claim 1, characterised in that the sequentially arranged working heads (A1 , A2, A3, A4) have an interspace (B) located therebetween.

4. Screwing tap according to claim 1, characterised in that the sequentially arranged working heads (A1 , A2, A3, A4) have coarse cutting threads (N) and finishing threads (S) formed thereon.

5. Screwing tap according to any preceding claim, characterised in that the diameter (C) of the interspace (B) located between sequentially arranged working heads (A1 , A2, A3, A4) is less than the diameter of an actual core boring.

6. Screwing tap according to claim 1, characterised in that the length (B) of the interspace (B) located between sequentially arranged working heads (A1 , A2, A3, A4) is preferably at most 5 times longer, than the actual pitch (p) of the working head (A1 , A2, A3).

7. Screwing tap according to claim 1, characterised in that the surface of the interspace (B) located between sequentially arranged working heads (A1 , A2, A3, A4) is provided with a groove (D) arranged circumferentially.