Tool for creating a threaded hole

Abstract

Tool for creating a threaded hole in a sheet-like piece of plasticly deformable material upon rotation of the tool about a longitudinal axis of the tool, comprising: at a longitudinal end thereof, a hole-forming portion configured for creating the hole; behind the hole-forming portion, as seen along the longitudinal axis, a threading portion configured for forming an internal thread in a circumferential wall of the hole in a non-cutting manner, the internal thread having a major diameter and a minor diameter; and between the threading portion and the hole-forming portion, a transition portion having a maximum cross-sectional diameter that is smaller than the minor diameter of the internal thread.

Description

l Tool for creating a threaded hole The present invention relates to a tool for creating a threaded hole in a sheet-like piece of plasticly deformable material. Forming holes instead of cutting holes is a known solution for creating holes in thin-walled objects, such as hollow box profiles or tubes. Forming is a fabrication technique wherein a material is plastically deformed due to an increase of temperature of the material without cutting away any material. Therefore, no material chips are created in the fabrication process. A widely used forming technique is friction forming. In a friction forming process, a tool creates friction between the tool and a surface of a plastically deformable material by rotating the tool. The friction subsequently creates heat in the material which renders the material plastically deformable. At this stage the tool is pushed into the surface to create a hole. Forming is favourable for thin objects, in particular if the formed hole is intended to be equipped with internal threading. By forming instead of cutting the hole, the material which was originally placed inside the hole is pushed towards a backside of the object instead of being completely removed. At this backside, the displaced material forms a protruding cylindrical wall with an inner diameter corresponding to the outer diameter of the forming tool. In this manner, the thickness of the object is locally increased to be able to create a longer internal thread. Longer internal threads provide the benefit that a connection therewith by the external thread of a bolt becomes stronger than with a smaller internal thread, as there is more room for engagement of the internal thread with the external thread. A known tool to perform such an operation combines a segment for hole creation and a subsequent segment for thread creation into a singular tool. By combining both operations in a single tool, operation time is minimised. Furthermore, the material thickness required to achieve sufficient engagement between internal threads and external threads is reduced. Any need for an intermediate alignment between fabrication steps and a tool change is eliminated as well. However, during use of such a combined tool problems typically arise such as inaccurate forming of threads or destruction of just-created threads. It is an object of the present invention to provide a combined tool for successfully forming a hole in sheet-like piece of plastically deformable material with internal threading that is according to specification. Hereto, the present invention provides, according to a first aspect thereof, a tool for creating a threaded hole in a sheet-like piece of plasticly deformable material upon rotation of the tool about an longitudinal axis of the tool, comprising: at a longitudinal end thereof, a hole-forming portion congured for creating the hole; behind the hole-forming portion, as seen along the longitudinal axis, a threading portion configured for forming an internal thread in a circumferential wall of the hole in a non-cutting manner, the internal thread having a major diameter and a minor diameter; and between the threading portion and the hole-forming portion, a transition portion having a maximum cross- sectional diameter that is smaller than the minor diameter of the internal thread. Thread-forming is also known as tapping. The threading portion creates an internal thread in the circumferential wall of the hole created by the hole-forming portion. The transition portion between the hole-forming portion and the threading portion with a maximum cross-sectional diameter that is smaller than the minor diameter of the forming portion provides room for the start of the thread-forming process by the threading portion. The smaller diameter of the transition portion enables the threading portion to properly engage in the circumferential wall of the hole without being interfered by material that is pushed in front of the threading portion by the hole-forming portion. After the threading portion has properly engaged with the material in the circumferential wall, following the transition portion, the diameter of the tool increases to the major and minor diameter corresponding to the desired thread size of the internal thread. International standards by organisations such as ISO or ASTM prescribe for different types of thread the major diameter, minor diameter, and pitch size. It is to be understood that the piece of sheet-like material is a relatively thin piece that could be part of, for example, a hollow extruded profile or a hollow tube. In a preferred embodiment of the present invention, the transition portion gradually tapers from a segment abutting the threading portion and / or a segment abutting the hole-forming portion towards a minimum cross-sectional diameter of the transition portion. The gradual increase in cross- sectional diameter of the tool in the transition portion allows for a smooth transition and decreases the likelihood of the tool getting stuck on the threading portion during operation of the tool and ensures a proper engagement of the threading portion in the circumferential wall without skipping a part thereof. Preferably, the hole-forming portion is configured to create the hole by cutting the hole. In a preferred embodiment of the present invention, the hole-forming portion is configured to make the hole by pushing the material out of the way with the aid of heat from friction between the hole-forming portion and the material upon rotation of the tool. Ordinarily, a conical shaped tip is used for friction forming. By rotating the tool against the material, friction therebetween is produced. Heat results from the friction. The material is chosen such that with this increase in heat, the material transitions from its elastic behaviour to plastic behaviour. After this transition into the plastic state, material of the object is permanently moved by the tool. The material that is pushed out of the way by means of a tool according to the preferred embodiment will accumulate at the other end of the object in which the hole is formed. The accumulated material will add extra length to the circumferential wall of the just formed hole. This allows the tool to form longer internal threading than the nominal thickness of the object was before the tool started forming a hole therein. With a longer internal thread, a stronger connection with the external thread of, for example, a bolt is possible in comparison to a threaded hole that is only the length of the thickness of the object in which it is made. Resulting in a stronger connection with the bolt that is screwed into the internal thread. In a preferred embodiment of the present invention, the threading portion is configured to make the internal thread by pushing the material in a thread shape upon rotation of the tool, optionally with the aid of residual heat present in the sheet-like piece of material generated by friction between the hole-forming portion and the material upon rotation of the tool. Forming of the internal thread in a non-cutting manner creates no material chips. In an environment where cleanliness is important, a lack of chips is benecial. Furthermore, forming of the threading also alters the density of the material abutting the internal thread. Material is partially pushed to the sides of the hole, thereby increasing the density of the material at that location. A local higher density of the material means that the strength of the internal threading itself becomes higher, which in turn will lead to a stronger connection between the internal thread and external thread. In a preferred embodiment of the present invention, an outer surface of the hole-forming portion near the transition portion is provided with a helical groove, wherein a pitch of the helical groove corresponds to a pitch of the threading portion, wherein the groove has an inner diameter that is smaller than or equal to the minor diameter of the threading portion. The maximum diameter of the hole-forming portion of the tool is bigger than the minor diameter of the threading portion of the tool. Therefore, to be able to retrieve the tool in a reversed motion, it is necessary to include a helical groove in the hole-forming portion of the tool with an inner diameter that is smaller than or equal to the minor diameter of the thread-forming tool. Matching the pitch of the groove to the pitch of the threading portion of the tool ensures a correct retrieval of the tool without damaging the internal thread. Retrieval of the tool out of the hole allows for a more efficient fabrication process and faster operations when a multitude of threaded holes have to be made. In this manner, hollow objects such as box profiles and pipes can be effectively provided with a threaded hole in one of their sides without interacting with the opposing side wall. In a preferred embodiment of the present invention, the groove comprises two parallel transitional edges at the intersection of the groove and the outer surface, wherein the transitional edges are rounded or chamfered. Providing transitional edges on the two edges of the groove, ensures a smooth retrieval of the tool. The transitional edges being rounded or chamfered ensures that the tool does not get stuck and does not damage the just created internal thread in the hole. In a preferred embodiment of the present invention, the hole-forming portion has a maximum cross-sectional diameter which is between the major diameter of the threading portion and the major diameter of the threading portion subtracted with a pitch of the threading portion. By selecting a cross-sectional diameter in this range, the right amount of material is present to form the internal thread in the circumferential wall of the hole. In this manner, there is no excess material which puts unnecessary stress on the tool. The matching of dimensions allows for optimal thread formation and is benecial for the longevity of the tool. Preferably, the hole-forming portion has a maximum cross-sectional diameter which is substantially in the middle between the major diameter of the threading portion and the minor diameter of threading portion. In a preferred embodiment of the present invention, the tool comprises a cutting edge behind the threading portion, as seen along the longitudinal axis. The cutting edge removes any material that is pushed out of the plastically deformable material by the threading portion. This material has accumulated on the top surface of the sheet-like piece of material, which is the surface from which the tool entered the piece of material during its operation. Cutting the excess material provides a smooth finish to the top surface of the plastically deformable material. According to a second aspect, the present invention provides a drilling apparatus for creating a threaded hole in a plasticly deformable material, comprising: a tool according to any of the preceding claims, and a drive device configured to rotate the tool about a longitudinal axis of the tool. A transition portion between the hole-forming portion and the threading portion with a maximum cross-sectional diameter smaller than the minor diameter of the hole-forming portion facilitates space for a correct start of the thread forming process by the threading portion of the tool. The threading portion creates an internal thread in the circumferential wall of the hole just created. In this manner, the threading portion is able to properly engage in the circumferential wall of the hole without being interfered by material that is pushed in front of the threading portion of the tool. After the threading portion has properly engaged following the transition portion, the diameter of the tool increases to the major and minor diameter that correspond to the desired thread size of the internal thread. Optionally, the tool is detachably mounted to the drilling apparatus. The drive device can be configured to be operated manually or automatically. The present invention is further illustrated by the following figures, which show a preferred embodiment of the surface cleaning system according to the invention, and are not intended to limit the scope of the invention in any way, wherein: - figure 1 shows a schematic side View of a tool according to a preferred embodiment of the present invention; - figure 2 shows a perspective view of a tool according to a preferred embodiment of the present invention; - figure 3 shows a detailed View of the tool shown in figure 1; and - figure 4 shows a cross-sectional profile view of the threading portion according to a preferred embodiment of the present invention. Figures 1 and 2 show a side view and a perspective view of a tool 100 for creating a threaded hole in a sheet-like piece of plasticly deformable material. The tool 100 is used to create a threaded hole in a plasticly deformable material with a singular piece of equipment. The tool 100 is rotated about its longitudinal axis L and pushed into the material. Friction between the material and the tool 100, caused by the rotation, provides heat in the material. With an appropriately selected material, enough heat will locally render the material plasticly deformable. First contact between the tool 100 and the material is at the tip 11 of the tool 100. The tip 11 of the tool 100 is part of the hole-forming portion 10 of the tool 100. The hole-forming portion 10 is provided with a conical shape, wherein the cross-sectional diameter of the hole-forming portion 10 increases from the tip 11 to a maximum cross- sectional diameter along the longitudinal axis L of the tool 100. The maximum cross-sectional diameter is matched to the middle between the maj or diameter 32 and the minor diameter 31 of the threading portion 30. In this manner, the tool 100 provides a hole with a diameter that corresponds to the correct predrilling diameter for the intended threaded hole. With a correct predrilling diameter, the right amount of material is present for the subsequent threading process. Threading is also known as tapping. An internal threading is formed in the hole just created by the threading portion 30 of the tool 100. The threading portion 30 has a grooved outer surface with a maximum cross-sectional diameter matching the major diameter of the intended internal threading of the threaded hole. The largest minimum cross-sectional diameter of the threading portion 30 is found at the bottom of the grooves and corresponds to the minor diameter of the internal threading. The deformable material is pushed in the intended shape by the threading portion 30. By matching the diameter of the hole formed by the hole-forming portion 10 to a suitable predrilling diameter of the hole, the required torque of the tool 100 to form the threading is minimised. Wear of the thread-forming tool is also reduced as a result, which is beneficial for the longevity of the tool. The tool 100 has a cyclic hexagonal cross-sectional profile, as is shown for the threading portion 30 in figure 4. The shape of the cross-sectional profile could also be any other cyclic polygonal cross-sectional profile, such as a triangle, square or pentagon. A polygonal shape allows the thread forming portion 30 to roll the thread in the hole just created as forming cavities 40 are provided between the hole just created and the tool 100. Because of the cyclic shape of the polygonal profile, meaning that all corners lie on a singular common circle 50, the resulting hole and thread are circularly shaped. The shown cross-sectional profile file shows a regular hexagon. The regular polygon shape helps with balancing the tool during the high-speed rotation of the tool necessary to create a sufficient amount of heat to shift the material into its plastic state locally. The corners of the hexagonal profile are rounded. To ensure a gradual movement of the tool 100 between the hole-forming operation and the threading operation and prevent the tool 100 from inaccurate thread formation, the tool 100 further comprises a transition portion 20 located between the hole-forming portion 10 and the threading portion 30. A more detailed View of the transition portion 20 is shown in figure 3. In this transition portion 20, additional room is given to the plasticly deformable material by reducing the cross- sectional diameter of the tool 100. In figure 3 the reduction is visualised with the difference in cross- sectional radii d1 and dz, respectively. The smaller diameter d2 of the transition portion 20 allows the threading portion 30 to properly engage in the inner wall of the hole just formed at the correct location along the length of the hole and form the threading as intended. The additional room is necessary to provide room for material that is pushed in front of the threading portion 30 by the hole-forming portion 10. After this transition portion 20, the threading portion 30 gradually increases its major and minor diameter 31, 32 with an initial angle a over the tapering segment D with respect to longitudinal axis L of the tool to the desired major and minor diameter 31, 32 of the internal threading it is forming. The outer profile of the tool 100 is visualised with dashed line P which represents the outer diameter of tool along its length. The angle of the tapering segment D gradually decreases from the initial angle a to zero at which point the outer surface of threading portion is arranged parallel to the longitudinal axis L of the tool 100. Finally, the tool 100 comprises a cutting edge 40 arranged behind the threading portion 30. The purpose of the cutting edge 40 is to remove any excess material that might have been pushed out of the hole above the top surface of the plasticly deformable material. Matching the cross-sectional diameter of the hole-forming portion 10 to the predrilling diameter of the intended threading minimises the amount of material that is pushed out. After the insertion of the tool 100 to a depth whereat the hole has been threaded to the desired depth, the tool 100 is retrieved by rotating the tool 100 about the longitudinal axis L in the reverse direction with respect to the insertion. The tool 100 is pulled backwards simultaneously. In the outer surface of the hole-forming portion 10 a helical groove 12 is provided near the transition portion 20 to not damage the internal threading just created in the hole during retrieval of the tool 100. The helical groove 12 possesses transitional edges 13 to the outer surface of the hole-forming portion 10. The transitional edges 13 further ensure smooth retrieval. The end of the threading portion 30 near the cutting edge 40 tapers with a clearance angel ß towards the longitudinal axis L of the tool 100 to provide sufficient clearance during retrieval of the tool 100. The figures are illustrative of selected aspects of the present disclosure, and together with the description serve to explain principles and operation of methods, products, and systems embraced by the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Since modifications, combinations, sub-combinations, and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to a person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

1. Tool for making a threaded hole in a plate-shaped piece plastically deformable material during rotation of the tool about a longitudinal axis of the tools, comprising: at a longitudinal end thereof, a hole-forming part designed to the hole to make; behind the hole-forming part, viewed along the longitudinal axis, a thread-forming part that is designed to cut an internal thread into a perimeter wall of the hole in a non-cutting manner forms, where the internal thread has an outer diameter and an inner diameter; and between the thread-forming part and the hole-forming part, a transition part with a maximum cross-sectional diameter that is smaller than the inner diameter of the internal thread.

2. Tools according to one of the preceding conclusions, whereby the transition section gradually tapers from a segment attached to the thread-forming part borders and / or a segment bordering the hole-forming part to a minimum cross-sectional diameter of the transition section.

3. Tooling according to one of the preceding claims, where the hole-forming The section is designed to create the hole by cutting the hole.

4. Tool within the meaning of claim 1 or 2, where the hole-forming part is designed to form the hole in a non-cutting manner.

5. Tool according to claim 4, where the hole-forming part is designed to make the hole by pushing the material aside using heat from friction between the hole-forming part and the material during rotation of the tool.

6. Tools according to one of the preceding conclusions, whereby the The thread-forming section is designed to create the internal thread through the material. to push into a threaded shape by rotation of the tool, optionally with the aid of the plate-shaped piece of material being present and by friction between the hole-forming part and the residual heat generated by the material during rotation of the tool.

7. Tool according to one of claims 4-6, where an outer surface of the hole-forming part near the transition section is provided with a spiral groove, where a pitch of the helical groove corresponds to a pitch of the thread-forming part, where the groove has an inner diameter that is less than or equal to the inner diameter of the thread-forming part.

8. Tool according to conclusion 7, where the groove two parallel includes transition edges at the transition of the groove and the outer surface, where the transition edges are rounded or beveled.

9. Tooling in accordance with one of the preceding claims, where the hole-forming part has a maximum cross-sectional diameter that is between the outer diameter of the thread-forming part and the outer diameter of the thread-forming part minus a pitch of the thread-forming part is.

10. Tooling according to one of the preceding claims, where the hole-forming part has a maximum cross-sectional diameter that is substantially in the middle between the outer diameter of the thread-forming part and the inner diameter of the is the thread-forming part.

11. Tool according to one of the preceding claims, comprising a cutting edge behind the thread-forming part, viewed along the longitudinal axis.

12. Drilling device for making a threaded hole in a plate-shaped piece plastically deformable material, comprising: a tool according to one of the preceding claims; and a drive device designed to move the tool around a longitudinal axis of the tool rotate.

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