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Title:
THREAD SHAPING TAP WITH MULTIPLE WORKING HEADS
Document Type and Number:
WIPO Patent Application WO/2004/043636
Kind Code:
A1
Abstract:
The invention discloses a new thread shaping 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).

Inventors:
Vilmányi, László (Hurok u. 5, Budapest, H-1091, HU)
Application Number:
PCT/HU2002/000175
Publication Date:
May 27, 2004
Filing Date:
December 28, 2002
Export Citation:
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Assignee:
Vilmányi, László (Hurok u. 5, Budapest, H-1091, HU)
International Classes:
B23G5/06; B23G7/02; (IPC1-7): B23G7/02; B23G5/06
Foreign References:
DE540731C
DE541880C
DE10002756A1
DE137171C
DE20109509U1
Attorney, Agent or Firm:
DANUBIA PATENT AND TRADEMARK ATTORNEYS (Bajcsy-Zsilinszky út. 16, Budapest, H-1051, HU)
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Claims:
Claims
1. Thread shaping tap having a first portion provided with working head, 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 (A1, A2, A3, A4) arranged sequentially along the length of the first portion (L).
2. Thread shaping tap according to claim 1., characterised in that the sequentially arranged working heads (A1, A2, A3, A4) have identical thread profile.
3. Thread shaping tap according to claim 1., characterised in that the sequentially arranged working heads (A1, A2, A3, A4) have an interspace (B) located therebetween.
4. Thread shaping tap according to claim 1., characterised in that the sequentially arranged working heads (A1, A2, A3, A4) have coarse shaping threads (N) and finishing threads (S) formed thereon.
5. Thread shaping 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. Thread shaping 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. Thread shaping 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.
Description:
THREAD SHAPING TAP WITH MULTIPLE WORKING HEADS

Technical field The invention relates to a thread shaping tap having a first portion provided with working head, 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 thread shaping tap is a tool frequently used to prepare threads into bore-holes. Contrary to the screwing taps chipping does not occur during operation of a thread shaping tap. The conventional thread shaping tap can be divided into two portions. A working head provided with entering and controlling portions is situated in the first end of a thread shaping 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 thread shaping taps according to the state of the art may be classified in accordance with their thread type, base material, use and way of production. The base material generally used for the thread shaping taps is the high-speed steel containing 5 wt% of cobalt (HSS-E).

Generally, the thread shaping taps having a maximum diameter of 12 mm are entirely made of tool steel or HSS-E material. In order to decrease the production costs the shaft of a thread shaping tap having a diameter above 12 mm is made of carbon steel causing lower costs. In order to increase the operating lifetime the working head of the thread shaping taps is provided with different coatings (TiN, TiCN).

In a common way, the length of the working head of a thread shaping 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 thread shaping taps being able to prepare more and more threads with a single tool.

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

The entering portion of a thread shaping tap functions as to form gradually the thread in the workpiece material. The threaded controlling portion following the entering portion of a tool functions as to control threads and to guide the entire tool.

Wearing, fractures and even hacks must be occurred on the thread shaping tap during loading. Due to a, higher loading these damages occur chiefly on the entering portion of the tool. The tool must be changed if above damage is so high, that it degrades essentially the thread shaping features of the tool.

With thread shaping taps according to the state of the art the thread forming operation is achieved actually by means of 1/6 part of the entire tool length. This is an unfavourably bad operating rate resulting in a large quantity of waste material and increased production costs.

Therefore, it is a need in the art to create a thread shaping tap having longer lifetime and an operating rate better than above rate, and to create a thread shaping 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 thread shaping taps.

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

The thread shaping tap according to the invention has a first portion provided with working head 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 shaping 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 thread shaping tap according to the invention showing the working heads formed sequentially in a tool, Figure 2. is a side elevation view of a thread shaping 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 thread shaping 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 thread shaping tap 1 with multiple working head A1, A2, A3 according to the present invention. The thread shaping 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 shaping threads N and a controlling portion consisting of finishing threads S. The coarse shaping threads N of the thread shaping tap 1 function as to shape firstly the workpiece material. The finishing threads S following the coarse shaping 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.

The coarse shaping 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 thread shaping 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 thread shaping tap 1 by means of a cutting device applied between working head A1 and A2. Consequently, the thread shaping tap 1 will be ready again to work by the working head A2.

Figure 2. shows a second embodiment of the thread shaping tap 1 according to the present invention. In this embodiment the thread shaping 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 thread shaping 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 thread shaping tap 1. This groove allows the material of the interspace B to be intentionally (only) broken away 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 thread shaping tap 1. Then the following working head A2, A3 will be ready to work immediately by a performance of 100%.

Examples A thread of 15 mm length (depth) was prepared into a blind bore-hole situated in a workpiece by a thread shaping 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 thread shaping tap damaged and disabled to work.

Then above operation was repeated by a thread shaping 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 thread shaping 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 thread shaping tap 1 with 4 working heads according to the invention and having a diameter d of 10 mm. 3 coarse shaping 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 thread shaping tap 1 was equal to the length of a conventional thread shaping tap having similar purpose. The conventional thread shaping tap disabled after preparing 1500 threads. With the thread shaping tap 1 according to the invention this number of threads prepared was 6050.

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

Therefore, principal advantages of thread shaping 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, with the use of thread shaping taps 1 according to the invention the overall tool costs per thread can be reduced to the half/third value relative to the similar costs of conventional thread shaping taps. In addition, the fewer thread shaping taps, the lesser waste material.