TOOL BIT
A tool bit includes a hexagonal drive portion and a working end having a core material and a cladding layer surrounding the core material. The cladding layer has a first hardness. The tool bit includes a shank interconnecting the drive portion and the working end. The shank has a second hardness. The first hardness is higher than the second hardness.
This application is a continuation of co-pending U.S. patent application Ser. No. 14/596,739 filed on Jan. 14, 2015, now U.S. patent Ser. No. 10/022,845, which claims priority to U.S. Provisional Patent Application No. 61/928,266 filed on Jan. 16, 2014, the entire contents of both of which are incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to tool bits, and more particularly to tool bits configured for interchangeable use with a driver.
BACKGROUND OF THE INVENTIONTool bits, or insert bits, are often used with drivers configured to interchangeably receive the bits. For example, typical insert bits each include a hexagonal drive portion, a head or tip configured to engage a fastener, and a cylindrical shank connecting the drive portion and the tip. Drivers include a socket having a hexagonal recess in which the hexagonal drive portion of an insert bit is received and a stem or shank extending from the socket, which can be coupled to a handle for hand-use by an operator, or a power tool (e.g., a drill) for powered use by the operator. An interference fit between the hexagonal drive portion of the insert bit and the socket may be used to axially secure the insert bit to the driver, or quick-release structure may be employed to axially secure the insert bit to the driver.
SUMMARY OF THE INVENTIONThe invention provides, in one aspect, a tool bit including a hexagonal drive portion and a working end having a core material and a cladding layer surrounding the core material. The cladding layer has a first hardness. The tool bit includes a shank interconnecting the drive portion and the working end. The shank has a second hardness. The first hardness is higher than the second hardness.
Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTIONWith continued reference to
In the illustrated embodiment of
In operation of the bit 10, the concavity of the shank 22 is configured to increase the impact resistance or the toughness of the bit 10, such that the drive portion 14 and the shank 22 of the bit 10 are allowed to elastically deform or twist relative to the tip 18 about a longitudinal axis of the bit 10. Specifically, the polar moment of inertia of the shank 22 is decreased by incorporating the concavity, thereby reducing the amount of torsion required to elastically twist the shank 22, compared to a shank having a cylindrical shape. The reduced hardness of the shank 22 relative to the tip 18 further increases the impact resistance of the bit 10, compared to a similar bit having a uniform hardness throughout.
In the particular embodiment of the bit 10a shown in
In the illustrated embodiment shown in
For the two-inch bit 10d shown in
With reference to
With reference to
The shank 22d includes slots 58 spaced about the peripheral surface 54 at 90 degree angular increments, with each of the slots 58 defining a minor longitudinal axis 62 (
With continued reference to
The hollow core 30 and the slots 58 in the tool bit 10d work in conjunction to increase the impact resistance or the toughness of the tool bit 10d, such that the tip 18d of the tool bit 10d is allowed to elastically deform or twist relative to the hexagonal drive portion 14d about the major longitudinal axis 38 of the tool bit 10d. Specifically, the polar moment of inertia of the shank 22d is decreased by incorporating the hollow core 30 and slots 58, thereby reducing the amount of torsion required to elastically twist the shank 22d, compared to a configuration of the shank having a solid cylindrical shape without the slots 58 (e.g., shanks 22, 22a, 22b).
In the illustrated embodiment of the tool bit 10d, the tip 18d made of a first material having a first hardness and the shank 22d is made of a second material having a second, different hardness. Particularly, the hardness of the tip 18d is greater than the hardness of the shank 22d to reduce the wear imparted to the tip 18d during use of the bit 10d. The reduced hardness of the shank 22d relative to the tip 18d, however, also increases the impact-resistance of the bit 10d. For example, the first hardness is about 55 HRC to about 65 HRC, with a nominal hardness of about 62 HRC, while the second hardness is about 40 HRC to about 55 HRC, with a nominal hardness of about 45 HRC. Therefore, a ratio between the first hardness and the second hardness is about 1:1 to about 1.7:1, with a nominal ratio of about 1.4:1. Alternatively, the ratio between the first hardness and the second hardness may be greater than about 1.7:1 to provide optimum performance of the tool bit 10d. The first and second materials are each comprised of a ferrous alloy composition, though different materials may alternatively be used.
As mentioned above, the two-shot metal MIM process is used to manufacture the bit 10d to make the conjoined tip 18d and shank 22d from two different materials. In other embodiments, the two-shot MIM process may be used to manufacture tool bits 10, 10a, 10b, and 10c. Particularly, in the illustrated embodiment of the tool bit 10d, the tip 18d is made from a material having a greater hardness than that of the shank 22d and the hexagonal drive portion 14d. Because the dissimilar materials of the tip 18d and the shank 22d, respectively, are conjoined or integrally formed during the two-shot MIM process, a secondary manufacturing process for connecting the tip 18d to the remainder of the bit 10d is unnecessary. Furthermore, the protrusion 40 provides a greater surface area between the tip 18d and the shank 22d so that the bond between dissimilar metals of the tip 18d and the shank 22d is stronger compared, for example, to using a flat mating surface between the tip 18d and the shank 22d. In addition, the protrusion 40 increases the shear strength of the bit 10d at the intersection of the tip 18d and the shank 22d.
With reference to
During the feedstock mixing process 70, the binder composition 82 is added to the first and the second materials 74, 78 to facilitate processing through the injection molding process 86. As a result, the first material 74, which is in a powder form, is homogeneously mixed with the binder composition 82 to provide a first feedstock mixture 102 of a determined consistency. In addition, the second material 78, which is also in a powder form, is also homogeneously mixed with the binder composition 82 to provide a second feedstock mixture 106 with substantially the same consistency as the first mixture 102. In the illustrated embodiment of the tool bit 10d, the binder composition 82 includes a thermoplastic binder. Alternatively, the binder composition 82 may include other appropriate binder compositions (e.g., wax). The amount of binder composition 82 in each of the first and second feedstock mixtures 102, 106 is chosen to match the shrink rates of the tip 18d and the drive portion 14d/shank 22d, respectively, during the sintering process 122 described below.
The injection molding process 86 includes processing the first and the second feedstock mixtures 102, 106 through an injection molding machine 134. Particularly, the process 86 includes injecting the first feedstock mixtures 102 into a first portion 110 of the mold 90, and injecting the second feedstock mixture 106 into a second portion 114 of the mold 90. In the illustrated embodiment shown in
The injection molding process 86 may be carried out in various ways to form the “green” tool bit 126. For example, the “green” tool bit 126 can be initially formed along the major longitudinal axis 38 from the hexagonal drive portion 14d to the tip 18, or from the tip 18d to the hexagonal drive portion 14d. Alternatively, the “green” tool bit 126 can be initially formed from a side-to-side profile as oriented in
After the injection molding process 86, the “green” tool bit 126 is removed from the mold 90 and proceeds through the debinding process 94. The debinding process 94 eliminates the binder composition 82. During the debinding process 94, the “green” tool bit 126 transforms into a “brown” tool bit 130 (as it is known in the MIM industry) that only includes the first and the second materials 74, 78. In the illustrated embodiment, the debinding process 94 includes a chemical wash 118. Alternatively, the debinding process 94 may include a thermal vaporization process to remove the binder composition 82 from the “green” tool bit 126. The “brown” tool bit 130 is fragile and porous with the absence of the binder composition 82.
To reduce the porosity of the “brown” tool bit 130, the heat treating process 98 is performed to atomically diffuse the “brown” tool bit 130 to form the final tool bit 10d. The heat treating process 98 exposes the “brown” tool bit 130 to an elevated temperature to promote atomic diffusion between the first and the second materials 74, 78, allowing atoms of the dissimilar materials 74, 78 to interact and fuse together. The heat treating process 98 reduces the porosity of the “brown” tool bit 130 to about 95% to about 99% to yield the final tool bit 10d. In the illustrated embodiment, the heat treating process 98 includes a sintering process 122. Alternatively, the debinding process 94 and the heat treating process 98 may be combined as a single process such that, at lower temperatures, thermal vaporization will occur during the debinding process 94 to eliminate the binder composition 82. And, at higher temperatures, atomic diffusion will reduce the porosity in the “brown” tool bit 130 to yield the final tool bit 10d.
Various features of the invention are set forth in the following claims.
Claims
1. A tool bit comprising:
- a hexagonal drive portion;
- a working end including a core material and a cladding layer surrounding the core material, the cladding layer having a first hardness; and
- a shank interconnecting the drive portion and the working end, the shank having a second hardness;
- wherein the first hardness is higher than the second hardness.
2. The tool bit of claim 1, wherein the first hardness of the cladding layer is higher than a hardness of the core material.
3. The tool bit of claim 2, wherein the shank and the core material are formed from the same material such that the second hardness of the shank is the same as the hardness of the core material.
4. The tool bit of claim 3, wherein the shank includes an outer peripheral surface, and wherein the outer peripheral surface has a curvature in a plane including a central axis of the tool bit.
5. The tool bit of claim 4, wherein the drive portion includes a groove configured to receive a quick-release structure to axially secure the tool bit to a driver.
6. The tool bit of claim 1, wherein the shank and the core material are formed from the same material such that the second hardness of the shank is the same as a hardness of the core material.
7. The tool bit of claim 6, wherein the first hardness of the cladding layer is higher than the hardness of the core material.
8. The tool bit of claim 7, wherein the shank includes an outer peripheral surface, and wherein the outer peripheral surface has a curvature in a plane including a central axis of the tool bit.
9. The tool bit of claim 8, wherein the drive portion includes a groove configured to receive a quick-release structure to axially secure the tool bit to a driver.
10. The tool bit of claim 1, wherein the shank includes an outer peripheral surface, and wherein the outer peripheral surface has a curvature in a plane including a central axis of the tool bit.
11. The tool bit of claim 10, wherein the shank and the core material are formed from the same material such that the second hardness of the shank is the same as a hardness of the core material.
12. The tool bit of claim 11, wherein the first hardness of the cladding layer is higher than the hardness of the core material.
13. The tool bit of claim 12, wherein the drive portion includes a groove configured to receive a quick-release structure to axially secure the tool bit to a driver.
14. The tool bit of claim 1, wherein the drive portion includes a groove configured to receive a quick-release structure to axially secure the tool bit to a driver.
15. The tool bit of claim 14, wherein the shank includes an outer peripheral surface, and wherein the outer peripheral surface has a curvature in a plane including a central axis of the tool bit.
16. The tool bit of claim 15, wherein the shank and the core material are formed from the same material such that the second hardness of the shank is the same as a hardness of the core material.
17. The tool bit of claim 16, wherein the first hardness of the cladding layer is higher than the hardness of the core material.
Type: Application
Filed: Jul 5, 2018
Publication Date: Nov 1, 2018
Inventor: Roger D. Neitzell (Palmyra, WI)
Application Number: 16/027,691