TOOL TIP ATTACHMENT FOR ULTRASONIC IMPACT GRINDING AND METHOD

Abstract

A replaceable tool tip system for an ultrasonic impact grinder includes a tool having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end. At least one threaded blind hole is disposed in the distal end of the tool. A replaceable tool tip includes at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole. At least one headless differential screw fastener has first threads for engaging a respective threaded blind hole on a first end and different second threads for engaging a respective through hole on a second end, and is used to attach and preload the replaceable tool tip.

Description

FIELD OF THE INVENTION

The subject matter disclosed herein relates to ultrasonic impact grinding and, in particular, to a replaceable tool tip for ultrasonic impact grinding of ceramic matrix composites (CMCs).

BACKGROUND OF THE INVENTION

Ceramic matrix composites (CMCs) may be formed of silicon carbide (SiC) fibers in a SiC matrix. The hardness of SiC/SiC CMCs is second only to that of diamond tooling. Additionally, the SiC fiber reinforced phase creates anisotropy and heterogeneity material properties. Therefore, it has been a challenge to develop an efficient and cost-effective way to perform high quality machining on such CMCs.

Ultrasonic impact grinding, also referred to as ultrasonic machining (USM), has been used to drill diffuser type of holes on CMCs. FIG. 1A shows a schematic of the basic elements of a typical loose abrasive USM tooling system 100. System 100 typically includes a back mass 102, transducer 110, flange (i.e., node) 104, front mass 106, step horn 120, and ultrasonic tool (i.e., tool) 130.

In operation, electrical energy input to the transducer 110 is converted to mechanical vibrations along its longitudinal axis A at high frequency (usually at 20-40 kHz). The excited vibration is subsequently transmitted through the energy-focusing horn 120 to amplify the vibration amplitude and finally delivered to the tool tip 135 of the ultrasonic tool 130. Thus, the tool 130 which is located directly above the workpiece can vibrate along its longitudinal axis with a desired amplitude 140 as shown in FIG. 1B.

As illustrated in FIG. 1B, an abrasive slurry 150 (comprising a mixture of abrasive material particles 155, e.g., diamond, boron carbide, etc. suspended in water or oil) is provided constantly into the machining area, which flushes away the debris from the working zone. The vibration of the tool 130 causes the abrasive particles 155 held in the slurry 150 between the tool tip 135 and the workpiece 160 to impact the workpiece surface causing material removal by microchipping. Since actual machining is carried out by the abrasive particles 155, the tool 130 can be made from a softer material than the workpiece. Essentially, the USM process is a large micro-cutting procedure, which involves abrasive particles cutting edges and can be understood as a micro scale material fracture process. The abrasive nature of the process has an impact not only on the workpiece 160, but also on the wear of the tool 130. Typical monolithic tools are made of titanium alloys due to desired properties such as density, toughness, and fatigue strength.

The above information disclosed in this Background section is only for understanding of the background of the inventive concepts and, therefore, it may contain information that does not constitute prior art.

SUMMARY OF THE INVENTION

The present disclosure is directed, in a first aspect, to a replaceable tool tip system for an ultrasonic impact grinder. The system includes a tool having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end, and at least one threaded blind hole disposed in the distal end of the tool. The system also includes a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole, and at least one headless differential screw fastener having first threads for engaging a respective threaded blind hole on a first end and having different second threads for engaging a respective through hole on a second end.

In an embodiment of the system, the at least one headless differential screw fastener may further include a recess for interfacing with a driving tool in the second end thereof.

In another embodiment of the system, the recess may be configured for interfacing with one of a cruciform head driver, a hex head driver, or a star head driver.

In a further embodiment of the system, the tool may be formed of titanium.

In yet another embodiment of the system, the replaceable tool tip may be made of a hardened tool steel.

In an embodiment of the system, the tool may include a plurality of first locating features disposed on the distal end thereof, and the replaceable tool tip may include a plurality of second locating features disposed on a proximal end thereof, the plurality of second locating features configured to interface with the first locating features.

In another embodiment of the system, the tool may have a pair of threaded blind holes and the replaceable tool tip may have a corresponding pair of threaded through holes.

In a further embodiment of the system, the first threads of the pair of threaded blind holes may be threaded opposite directions and the second threads of the pair of threaded through holes may be threaded in corresponding opposite directions.

In yet another embodiment of the system, the first threads of each threaded blind hole may be threaded in a first direction and the second threads of each threaded through hole may be threaded in a second direction opposite the first direction.

In an embodiment of the system, the first threads of each threaded blind hole may have a first pitch and the second threads of each threaded through hole may have a second pitch different from the first pitch.

The present disclosure is also directed, in a second aspect, to a method for replacing a tool tip for an ultrasonic impact grinder having a tool with a proximal end adjacent a horn of the ultrasonic impact grinder and an opposing distal end. The method includes: providing at least one threaded blind hole in the distal end of the tool; providing a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole; and rotating at least one headless differential screw fastener having first threads for engaging a respective threaded blind hole on a first end and having different second threads for engaging a respective through hole on a second end to attach the replaceable tool tip to the distal end of the tool and provide a preload force to the replaceable tool tip.

In an embodiment of the method, the at least one headless differential screw fastener may be rotated by a driving tool engaging a recess in the second end thereof.

In another embodiment of the method, the driving tool may use one of a cruciform head driver, a hex head driver, or a star head driver.

In a further embodiment of the method, the tool may be formed of titanium and the replaceable tool tip may be made of a hardened tool steel.

In yet another embodiment, the method may further include providing a plurality of first locating features disposed on the distal end of the tool, providing a plurality of second locating features disposed on a proximal end of the replaceable tool tip, and interfacing the plurality of second locating features with the first locating features when attaching the replaceable tool tip to the distal end of the tool.

In an embodiment of the method, providing the at least one threaded blind hole in the distal end of the tool may include providing a pair of threaded blind holes, providing at least one threaded through hole in the replaceable tool tip may include providing a corresponding pair of threaded through holes, and the first threads of the pair of threaded blind holes may be threaded in opposite directions and the second threads of the pair of threaded through holes may be threaded in corresponding opposite directions.

In another embodiment of the method, the first threads of each threaded blind hole may be threaded in a first direction and the second threads of each threaded through hole may be threaded in a second direction opposite the first direction.

In a further embodiment of the method, the first threads of each threaded blind hole may have a first pitch and the second threads of each threaded through hole may have a second pitch different from the first pitch.

The present disclosure is further directed, in a third aspect, to a replaceable tool tip system for an ultrasonic impact grinder. The system includes: a tool formed of titanium, the tool extending axially and having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end including a plurality of first locating features; a pair of threaded blind holes disposed in the distal end of the tool; a replaceable tool tip formed of hardened tool steel, the replaceable tool tip having pair of threaded through holes in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole, a proximal end of the replaceable tool tip includes a plurality of second locating features configured to interface with the plurality of first locating features, and a distal end of the replaceable tool tip includes a plurality of axially-extending walls in a substantially “π” shape; and a pair of headless differential screw fasteners having first threads on a first end for engaging a respective threaded blind hole, having different second threads on a second end for engaging a respective through hole, and having a recess on the second end thereof for engaging a rotating driving tool.

In an embodiment of this system, the first threads and second threads of each headless differential screw may be differential by being disposed opposite of each other or by having different pitches.

BRIEF DESCRIPTION OF FIGURES

The features of the disclosure believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The disclosure itself, however, both as to organization and method of operation, can best be understood by reference to the description of the preferred embodiment(s) which follows, taken in conjunction with the accompanying drawings in which:

FIG. 1A is a schematic diagram of an ultrasonic impact grinder usable with the present disclosure;

FIG. 1B is a close-up schematic view of loose abrasive ultrasonic machining usable with the present disclosure;

FIG. 2 is a perspective view of an embodiment of a replaceable tool tip in accordance with the present disclosure;

FIG. 3A is an exploded perspective view of an embodiment of a replaceable tool tip system in accordance with the present disclosure;

FIG. 3B is a perspective cutaway view of an embodiment of a replaceable tool tip being assembled to a tool in accordance with the present disclosure;

FIG. 3C is a perspective see-thru view of an embodiment of a replaceable tool tip in position on a tool in accordance with the present disclosure; and

FIG. 4 is a flow diagram of an example method in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present disclosure can comprise, consist of, and consist essentially of the features and/or steps described herein, as well as any of the additional or optional ingredients, components, steps, or limitations described herein or would otherwise be appreciated by one of skill in the art.

The following discussion omits or only briefly describes conventional features of the disclosed technology that are apparent to those skilled in the art. Reference to a particular embodiment does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are intended to be non-limiting and merely set forth some of the many possible embodiments for the appended claims. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. A person of ordinary skill in the art would know how to use the instant invention, in combination with routine experiments, to achieve other outcomes not specifically disclosed in the examples or the embodiments.

Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art in the field of the disclosed technology. It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless otherwise specified, and that the terms “includes” and/or “including,” when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Additionally, methods, equipment, and materials similar or equivalent to those described herein can also be used in the practice or testing of the disclosed technology.

The devices of the present disclosure may be understood more readily by reference to the following detailed description of the embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this application is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting. All spatial references, such as, for example, proximal, distal, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references “upper” and “lower” are relative and used only in the context to the other, and are not necessarily “superior” and “inferior.”

It will further be understood that, although the terms “first,” “second,” “third,” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, “a first element” discussed below could be termed “a second element” or “a third element,” and “a second element” and “a third element” may be termed likewise without departing from the teachings herein.

Various examples of the disclosed technology are provided throughout this disclosure. The use of these examples is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified form. Likewise, the invention is not limited to any particular preferred embodiment(s) described herein. Indeed, modifications and variations of the invention may be apparent to those skilled in the art upon reading this specification, and can be made without departing from its spirit and scope. The invention is therefore to be limited only by the terms of the claims, along with the full scope of equivalents to which the claims are entitled.

As discussed in the Background above, typical monolithic tools of ultrasonic vibration tools/ultrasonic impact grinders used in ultrasonic machining (USM) are made of titanium alloys due to desired properties such as density, toughness and fatigue strength. However, recent experiments have shown that the life of the tool tip can be extended if it is made of hardened tool steel rather than titanium having a lower hardness. Accordingly, it is an object of the present disclosure to provide a tool tip attachment and method to increase productivity and reduce the operational cost of the process.

In accordance with the present disclosure, a thread-based method may be used for attachment of a replaceable tool tip to the ultrasonic tool. This method allows for a quick and reliable connection of the titanium tool with a replaceable tool tip made of a different material, such as a hardened tool steel. It is important for the impact grinding process that the replaceable tool tip is in good contact with the tool for efficient energy transfer. Therefore, an adequate preload force must be applied to avoid separation of those two parts. The preload force must be greater than the force generated by the mass and acceleration of the replaceable tool tip.

In addition, the connection should preferably be obtained at the minimum depth (in the axial direction of the tool) due to high strain of the tool close to the working end. A central screw could be used for a replaceable tool tip having cyclic symmetry, however more complicated shapes may require different approach such as a pair of screws. Due to space considerations, headless differential screws may be used to provide the adequate preload between the tool and replaceable tool tip mating surfaces. The precise location of the replaceable tool tip may be established by locating features such as corner features, and preload may be provided by torqueing the screws simultaneously with a driver, such as a hex wrench, through the access holes provided by through holes in the replaceable tool tip. The differential screws, either using opposing threads or threads of different pitches, draw the parts together when rotated.

Accordingly, one or more embodiments of the present disclosure are directed to a replaceable tool tip system and method for an ultrasonic impact grinder (i.e., ultrasonic vibration tool) having a tool with a proximal end adjacent a horn of the ultrasonic impact grinder and an opposing distal end. At least one threaded blind hole is disposed in the distal end of the tool for attachment to a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole. A first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole such that at least one headless differential screw fastener can be used to attach the replaceable tool tip to the tool. The headless differential screw fastener has first threads for engaging a respective threaded blind hole on a first end and has different second threads for engaging a respective through hole on a second end, such that turning the headless differential screw fastener(s) with a driver tool pulls the tool and replaceable tool tip together and creates sufficient preload on the replaceable tool tip. With the replaceable tool tip made of hardened tool steel, productivity may be increased and operational costs decreased.

With reference to FIG. 2, a replaceable tool tip system 200 for an ultrasonic impact grinder is illustrated.

System 200 includes a tool 230 having a proximal end adjacent a horn of the ultrasonic impact grinder (see FIG. 1A) and a distal end. The distal end may be shaped for directing acoustic energy and may include another horn 232, for example, that tapers or expands from a circular shape of tool 230 to a shape of a replaceable tool tip 235. Tool 230 may be formed of a titanium alloy.

Although not visible in FIG. 2, at least one threaded blind hole is disposed in the distal end of the tool 230. Since two fasteners are illustrated in this embodiment, a pair of threaded blind holes would be disposed in the distal end of tool 230.

System 200 also includes a replaceable tool tip 235 having at least one threaded through hole in registration with each threaded blind hole. The replaceable tool tip 235 may be made from a different material, such as a hardened steel alloy (i.e., a hardened tool steel) having a Rockwell Hardness Rockwell C Scale (HRC) between 35-65. To connect the replaceable tool tip 235 to the distal end of tool 230, the system 200 includes at least one headless differential screw fastener 280. The headless differential screw fastener 280 may be formed of any suitable material, such as a high strength steel alloy.

The headless differential screw fastener 280 includes first threads for engaging a respective threaded blind hole on a first end and has different second threads for engaging a respective through hole on a second end. A first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole in order to engage with the headless differential screw fastener.

As used herein, a “differential screw fastener” refers to screw fastener that includes two different threaded portions that rotate about the same axis such than when the screw fastener is rotated, parts engaging the two different threaded portions will move relative to one another. When rotated in one direction, the parts will move towards each other, and when rotated in the other direction, the parts will move away from each other. This may be accomplished by using opposite right hand (RH) threads and left hand (LH) threads on the screw fastener or by using threads oriented in the same direction (RH or LH), but which have different pitches on the screw fastener.

By being headless, the headless differential screw fastener 280 avoids excess weight/mass at the tool tip. Since it is headless, the at least one headless differential screw fastener 280 may further include a recess 282 for interfacing with a driving tool in at least the second end thereof. Suitable recesses 282 and associated driving tools include, but are not limited to hex heads/drivers, cruciform (e.g., Phillips) heads/drivers, and star (e.g., Torx) heads/drivers. Accordingly, in various embodiments, the recess 282 may be configured for interfacing with one of a cruciform head driver, a hex head driver, or a star head driver, which may be in the form of a wrench having a suitable bit or head.

In one or more embodiments, the tool 230 may include a plurality of first locating features 240 disposed on the distal end thereof, and the replaceable tool tip 235 may include a plurality of second locating features 242 disposed on a proximal end thereof, with the plurality of second locating features 242 configured to interface with the first locating features 240. In the illustrated example, the first locating features 240 may be recessed portions and the second locating features 242 may be corresponding projecting portions. In other embodiments, the first locating features 240 may be projecting portions and the second locating features 242 may be corresponding recessed portions. In further embodiments, peripheral portions may contain complementary keyed surfaces or the like for the first and second locating features 240 and 242.

As illustrated in FIG. 2, the replaceable tool tip 235 may include thin walls 270 extending in a substantially axial direction to form the distal end of the replaceable tool tip 235. Such walls 270 reduce the weight/mass of the replaceable tool tip 235, yet may still interface with particles in a slurry during ultrasonic machining. In the illustrated embodiment, the walls are formed in a substantially “π” shape, but embodiments are not limited thereto.

In the embodiment of FIG. 2, the tool 230 has a pair of threaded blind holes (not seen) and the replaceable tool tip 235 has a corresponding pair of threaded through holes for headless differential screw fasteners 280. In such a case, the headless differential screw fasteners 280 may take various forms. In one embodiment, the first threads of the pair of threaded blind holes are threaded opposite directions and the second threads of the pair of threaded through holes are threaded in corresponding opposite directions. In such a case, the headless differential screw fasteners 280 may have driver recesses 282 in both ends to permit the same part to used, albeit with one reversed relative to the other.

In another embodiment, the first threads of each threaded blind hole may be threaded in a first direction and the second threads of each threaded through hole may be threaded in a second direction opposite the first direction. In such a case, the headless differential screw fasteners 280 may only require driver recesses 282 in one end thereof.

In a further embodiment, the first threads of each threaded blind hole may have a first pitch and the second threads of each threaded through hole may have a second pitch different from the first pitch. In such a case, the headless differential screw fasteners 280 may only require driver recesses 282 in one end thereof.

Additional details of the embodiment disclosed in system 200 are illustrated in FIGS. 3A, 3B, and 3C.

FIG. 3A illustrates an exploded perspective view of an embodiment of a replaceable tool tip system in accordance with the present disclosure. FIG. 3A illustrates how the headless differential screw fasteners 380 may be disposed between the distal end of tool 330 and replaceable tool tip 335, and that wrenches or other driving tools 390 may originally be disposed on a distal side of the replaceable tool tip 335.

As illustrated in FIG. 3B, the wrenches or driving tool 390 may access the recesses in headless differential screw fasteners 380 via the threaded through hole(s) 384. The driving tool(s) 390 may then be rotated such that first threads 381 engage the threads of threaded blind hole(s) 386 and second threads 383 engage the threads of threaded through hole 384. In this embodiment, the first threads 381 and second threads 383 may be oppositely threaded (i.e., RH and LH or LH and RH).

In an embodiment where the first threads 381 and 383 have different pitches, the diameter of first threads 381 may be smaller so as to pass through threaded through holes 384, but have a slightly lower pitch so as to progress differentially faster within corresponding threaded blind holes 386 in order to achieve the desired preload.

FIG. 3C illustrates a perspective see-thru view of an embodiment of a replaceable tool tip 335 in position on a tool in accordance with the present disclosure. As shown, the threaded blind holes 386 should be slightly deeper than the first threads 381 to avoid bottoming out before the desired preload is achieved. The second locating features 342 interface with complementary first locating features on the tool to keep the replaceable tool tip 335 in the correct position on the tool, and walls 370 extend axially to form the distal end of replaceable tool tip 335.

Thus, in an embodiment, a replaceable tool tip system for an ultrasonic impact grinder may include: a tool 330 formed of titanium, the tool 330 extending axially and having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end including a plurality of first locating features; a pair of threaded blind holes 386 disposed in the distal end of the tool 330; a replaceable tool tip 335 formed of a hardened tool steel, the replaceable tool tip 335 having pair of threaded through holes 384 in registration with each threaded blind hole 386, wherein a first threading of each threaded blind hole 386 is different from a second threading of each corresponding threaded through hole 384, a proximal end of the replaceable tool tip includes a plurality of second locating features 342 configured to interface with the plurality of first locating features, and a distal end of the replaceable tool tip 335 includes a plurality of axially-extending walls 370 in a substantially “π” shape; and a pair of headless differential screw fasteners 380 having first threads 381 on a first end for engaging a respective threaded blind hole 386, having different second threads 383 on a second end for engaging a respective through hole 384, and having a recess on the second end thereof for engaging a rotating driving tool 390.

In an embodiment, the first threads 381 and second threads 383 of each headless differential screw 380 are differential by being disposed opposite of each other or by having different pitches.

FIG. 4 is a flow diagram of an example method 400 for replacing a tool tip for an ultrasonic impact grinder having a tool with a proximal end adjacent a horn of the ultrasonic impact grinder and an opposing distal end in accordance with the present disclosure.

The method includes a step 410 of providing at least one threaded blind hole in the distal end of the tool.

The method 400 also includes a step 420 of providing a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole.

Step 430 of method 400 includes rotating at least one headless differential screw fastener having first threads for engaging a respective threaded blind hole on a first end and having different second threads for engaging a respective through hole on a second end to attach the replaceable tool tip to the distal end of the tool. In various embodiments, the at least one headless differential screw fastener may be rotated by a driving tool engaging a recess in the second end thereof. In further embodiment, the driving tool may use one of a cruciform head driver, a hex head driver, or a star head driver.

Method 400 further includes a step 440 of torqueing the at least one headless differential screw fastener to provide a preload force to the replaceable tool tip.

In various embodiments of method 400, the tool may be formed of titanium and the replaceable tool tip may be made of hardened tool steel. Other embodiments of method 400 may include providing a plurality of first locating features disposed on the distal end of the tool, providing a plurality of second locating features disposed on a proximal end of the replaceable tool tip, and interfacing the plurality of second locating features with the first locating features when attaching the replaceable tool tip to the distal end of the tool.

In other variations of method 400, step 410 of providing the at least one threaded blind hole in the distal end of the tool includes providing a pair of threaded blind holes, the step 420 of providing at least one threaded through hole in the replaceable tool tip includes providing a corresponding pair of threaded through holes, the first threads of the pair of threaded blind holes may be threaded in opposite directions, and the second threads of the pair of threaded through holes may be threaded in corresponding opposite directions.

In one or more embodiments, the first threads of each threaded blind hole may be threaded in a first direction and the second threads of each threaded through hole may be threaded in a second direction opposite the first direction.

In other embodiments, the first threads of each threaded blind hole may have a first pitch and the second threads of each threaded through hole may have a second pitch different from the first pitch.

Embodiments in accordance with the present disclosure enable the use of different materials for the replaceable tool tip that may be cheaper and/or more durable, such as hardened tool steel. The disclosed embodiments permit simple installation via a driving tool (wrench) that is amenable to automation. Embodiments in accordance with the present disclosure provide a low profile, compact attachment solution for replaceable tool tips. Indeed, tool tips in accordance with the present disclosure may be replaced without the need to remove the entire tool from the ultrasonic driving device and may thus reduce setup time.

While the present disclosure has been particularly described, in conjunction with specific preferred embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present disclosure.

Claims

1. A replaceable tool tip system for an ultrasonic impact grinder, comprising:

a tool having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end;

at least one threaded blind hole disposed in the distal end of the tool;

a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole; and

at least one headless differential screw fastener having first threads for engaging a respective threaded blind hole on a first end and having different second threads for engaging a respective through hole on a second end.

2. The replaceable tool tip system of claim 1, wherein the at least one headless differential screw fastener further includes a recess for interfacing with a driving tool in the second end thereof.

3. The replaceable tool tip system of claim 2, wherein the recess is configured for interfacing with one of a cruciform head driver, a hex head driver, or a star head driver.

4. The replaceable tool tip system of claim 1, wherein the tool is formed of titanium.

5. The replaceable tool tip system of claim 1, wherein the replaceable tool tip is made of hardened tool steel.

6. The replaceable tool tip system of claim 1, wherein:

the tool includes a plurality of first locating features disposed on the distal end thereof; and

the replaceable tool tip includes a plurality of second locating features disposed on a proximal end thereof, the plurality of second locating features configured to interface with the first locating features.

7. The replaceable tool tip system of claim 1, wherein the tool has a pair of threaded blind holes and the replaceable tool tip has a corresponding pair of threaded through holes.

8. The replaceable tool tip system of claim 7, wherein the first threads of the pair of threaded blind holes are threaded opposite directions and the second threads of the pair of threaded through holes are threaded in corresponding opposite directions.

9. The replaceable tool tip system of claim 1, wherein the first threads of each threaded blind hole is threaded in a first direction and the second threads of each threaded through hole is threaded in a second direction opposite the first direction.

10. The replaceable tool tip system of claim 1, wherein the first threads of each threaded blind hole have a first pitch and the second threads of each threaded through hole has a second pitch different from the first pitch.

11. A method for replacing a tool tip for an ultrasonic impact grinder having a tool with a proximal end adjacent a horn of the ultrasonic impact grinder and an opposing distal end, the method comprising:

providing at least one threaded blind hole in the distal end of the tool;

providing a replaceable tool tip having at least one threaded through hole in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole; and

rotating at least one headless differential screw fastener having first threads for engaging a respective threaded blind hole on a first end and having different second threads for engaging a respective through hole on a second end to attach the replaceable tool tip to the distal end of the tool and provide a preload force to the replaceable tool tip.

12. The method of claim 11, wherein the at least one headless differential screw fastener is rotated by a driving tool engaging a recess in the second end thereof.

13. The method of claim 12, wherein the driving tool uses one of a cruciform head driver, a hex head driver, or a star head driver.

14. The method of claim 1, wherein the tool is formed of titanium and the replaceable tool tip is made of hardened tool steel.

15. The method of claim 11, further comprising:

providing a plurality of first locating features disposed on the distal end of the tool;

providing a plurality of second locating features disposed on a proximal end of the replaceable tool tip; and

interfacing the plurality of second locating features with the first locating features when attaching the replaceable tool tip to the distal end of the tool.

16. The method of claim 11, wherein:

providing the at least one threaded blind hole in the distal end of the tool includes providing a pair of threaded blind holes;

providing at least one threaded through hole in the replaceable tool tip includes providing a corresponding pair of threaded through holes; and

the first threads of the pair of threaded blind holes are threaded in opposite directions and the second threads of the pair of threaded through holes are threaded in corresponding opposite directions.

17. The method of claim 11, wherein the first threads of each threaded blind hole is threaded in a first direction and the second threads of each threaded through hole is threaded in a second direction opposite the first direction.

18. The method of claim 11, wherein the first threads of each threaded blind hole have a first pitch and the second threads of each threaded through hole has a second pitch different from the first pitch.

19. A replaceable tool tip system for an ultrasonic impact grinder, comprising:

a tool formed of titanium, the tool extending axially and having a proximal end adjacent a horn of the ultrasonic impact grinder and a distal end including a plurality of first locating features;

a pair of threaded blind holes disposed in the distal end of the tool;

a replaceable tool tip formed of hardened tool steel, the replaceable tool tip having pair of threaded through holes in registration with each threaded blind hole, wherein a first threading of each threaded blind hole is different from a second threading of each corresponding threaded through hole, a proximal end of the replaceable tool tip includes a plurality of second locating features configured to interface with the plurality of first locating features, and a distal end of the replaceable tool tip includes a plurality of axially-extending walls in a substantially “π” shape; and

a pair of headless differential screw fasteners having first threads on a first end for engaging a respective threaded blind hole, having different second threads on a second end for engaging a respective through hole, and having a recess on the second end thereof for engaging a rotating driving tool.

20. The replaceable tool tip system of claim 19, wherein the first threads and second threads of each headless differential screw are differential by being disposed opposite of each other or by having different pitches.