WO2023102007A1

WO2023102007A1 - Backup pads and methods of using the same

Info

Publication number: WO2023102007A1
Application number: PCT/US2022/051334
Authority: WO
Inventors: Jacob S. BEVERIDGE; Paul N. Daveloose; Ryohei TOMIHARA; Nicholas B. Manor
Original assignee: 3M Innovative Properties Company
Priority date: 2021-12-03
Filing date: 2022-11-30
Publication date: 2023-06-08

Abstract

An abrasive article mounting assembly is presented. The abrasive article mounting assembly includes a backup pad. The assembly also includes a tool engaging aperture that receives a shaft of a tool. The assembly also includes a backup pad face. The assembly also includes a centering feature that maintains a position of an abrasive article on the backup pad face. The centering feature protrudes from the backup pad face. The assembly also includes a fastener that couples the backup pad to the shaft.

Description

BACKUP PADS AND METHODS OF USING THE SAME

BACKGROUND

Many types of abrasive articles are used in a number of industries to remove material from or polish a workpiece. In one common use, an abrasive article with a central arbor hole is mounted to a back-up pad that is driven by a rotating power shaft of an angle grinder. The back-up pad allows the operator to exert pressure toward a workpiece being abraded while mitigating any deformation of the disc. Some such back-up pads have raised ridges that can localize pressure against adjacent portions of the disc, resulting in increased abrading rate.

SUMMARY

Features and advantages of the present disclosure will be further understood upon consideration of the drawings and detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B illustrate schematic perspective views of repositionable abrasive disc mounting assemblies retaining an abrasive disc and mounted on a drive shaft of a power tool.

FIG. 2 illustrates a method of replacing a first abrasive article with a second abrasive article.

FIGS. 3A and 3B illustrate views of an abrasive article on a grinding tool.

FIGS. 4A-4E illustrate a backup pad in accordance with embodiments herein.

FIGS. 5A-5B illustrate a backup pad in accordance with some embodiment herein.

FIGS. 6A-6F illustrate profiles of a centering ring for a backup pad in accordance with some embodiments herein. FIG. 7 illustrates a method of removing a backup pad from a tool in accordance with embodiments herein.

FIG. 8 illustrates a method of centering an abrasive article on a backup pad in accordance with embodiments herein.

FIG. 9 illustrates a block diagram of a backup pad in accordance with embodiments herein.

FIGS. 10A-1 to 10C-3 illustrate different backup pads being attached to a power tool.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Referring now to FIGS. 1A-1B, an abrasive disc assembly 100 includes a back-up pad 110 and a fastener 140 that secures an abrasive disc 20. A threaded drive shaft 10 of a power tool (not shown) such as, for example, an angle grinder is engaged by the backup pad and held in place by a fastener, such as a nut, bolt or other fastener 140.

When engaged to a tool, shaft 10 spins about axis 115. As illustrated in FIG. IB, fastener 140 protrudes above a plane of abrasive article 20. Therefore, an area 22 of an abrasive disc 20 near fastener 140 may not be used, or not used to the same extent as an area 24 of abrasive disc 20 further from fastener 140. This results in wasted abrasive particles, resin and backing materials. Additionally, because an abrasive disc is often used at an angle (e.g. between 5°-15° with respect to the workpiece) with a rotational grinding tool. This means that the center area of the disc does not contact the worksurface, resulting in unused abrasive and waste.

An abrading system is desired that results in less material waste, which may provide a cost reduction to manufacturers and consumers, and generally is more sustainable.

As described with respect to embodiments herein, a backup pad couples to an abrasive article and provides support for an abrasive article during an abrasive operation. A backup pad may be made of a variety of materials, and different backup pads may be useful for different operations. For example, contour work or finishing may benefit from a cushioned or flexible backup pad, while a grinding operation may benefit from a more rigid backup pad. As described herein, backup pads may be made from any suitable plastic material, depending on operational needs. For example, rubber, nylon, PVT, PEEK, PPE, PPU, PPP, TPU, TPE resin polymers with or without fillers (e.g. glass or glass fiber to impart hardness or robustness or other qualities) or any copolymers thereof. The material may have a hardness or rigidity selected for operational appropriateness. Additionally, in some embodiments, a backup pad is made of thermoset material instead of thermoplastic. For example, phenolic reasons, epoxies, acrylates, etc. Further, in some embodiments a combination of materials is used, for example a thermoset material for a first component and a thermoplastic for a second.

FIG. 2 illustrates a method of replacing a first abrasive article with a second abrasive article. Abrasive articles include abrasive particles within or on top of a substrate, among other components such as resin, lubricant, etc. Over time, the abrasive particles are worn down until the abrasive article needs to be replaced. Similarly, a backup pad also needs to be replaced periodically, or may be switched for a different backup pad for a different abrasive component. Method 200 may be useful for switching out components in a variety of scenarios.

In block 210 a current component is in use on a tool. For example, for a given operation an angle grinder may have a specific backup pad 212 coupled to an abrasive article, such as a disc 214, nonwoven pad 216, grinding wheel 218 or other article 219.

In block 220, a need arises to switch one or more components of an abrasive system. For example, after a majority of material has been removed by a grinding wheel, it may be necessary to finish a workpiece with a finer abrasive article. This may require replacement of both a backup pad as well as the abrasive article attached. This may require removal of the abrasive article from the backup pad, the backup pad from the tool, or both.

In block 230, the new components are used. For example, a different backup pad 232 may be used, a different abrasive disc 234, a different nonwoven pad 236, a different grinding wheel 238, and / or another different component 239 may be used.

It is necessary for a backup pad to be easily configurable by a user. In many embodiments herein, a backup pad is designed to exchangeably receive an abrasive article, for example using a Dual Lock™ hook and loop fastener or other removeable fastener. However, it is also contemplated that an abrasive article may be adhered into place using adhesive, or an adhesiveless method such as friction welding or ultrasonic welding. Similarly, it is important for a backup pad to be easily removed from a tool. The backup pad may receive a spindle of a tool, either using threading or another mechanism. The backup pad may then be locked in place using a fastener such as a nut, bolt or other removeable fastener.

It is important that any backup pad solution be easily engaged to, and removed from, a tool, and to receive an abrasive article of choice.

FIGS. 3A and 3B illustrate views of an abrasive article on a grinding tool. As noted above, many customers do not utilize the interior area, causing waste of abrasive particles and any binder / resin, embedded lubricant, etc. In order to reduce waste, system 300 uses an abrasive article 302 with a larger aperture with radius 308, and a useable portion 304 of a radius 306. Table 1 below illustrates a comparison of areas of abrasive articles contemplated herein, compared to traditional areas of similarly sized discs. Table 1 shows Outer Diameters (OD) of abrasive articles, and Inner Diameters (ID) of abrasive articles as used herein.

Table 1: Comparison of outer diameter and inner diameters of abrasive articles.

Abrasive article 302 is coupled to an abrasive article, located directly behind disc 302 and not explicitly visible in FIGS. 3A-3B. A fastener 310 is used to couple backup pad to a tool (not shown). Fastener 310 can be removed using a spanner wrench, received by apertures 314, for example. However, while the design of disc 302 provides less waste than similarly sized conventional abrasive disc, it also presents less surface area for sufficient coupling to a backup pad. This can cause shifting of the abrasive disc to occur during use, which can result in suboptimal abrading and vibration to the user due to the imbalance of the abrasive disc on the backup pad. Additionally, an eccentric disc can hit the safety cover of a grinder, which requires the grinder be stopped.

FIGS. 4A-4E illustrate a backup pad in accordance with embodiments herein. A backup pad 400 is illustrated in FIG. 4A. FIG. 4B illustrates a perspective cutaway view 430 and FIG. 4C illustrates an end-on cutaway view 450. Backup pad 400 has a backup pad face 410, a centering ring 420, and a tool fastening area 430, which can include a threaded aperture or an X-lock type system for easy attachment to a grinding tool. Other attachment mechanisms are also contemplated. Backup pad 400 has a diameter 412, and centering ring 422 has a radius 422.

As illustrated in FIG. 4C, a tool-engaging area has a depth 456 that is deeper than a height 452 of centering ring. Height 452 may be selected to be similar to the height of an abrasive article that is received about centering ring 420. Having a relatively coplanar surface of an abrasive article, top of centering ring 420 and the top of a fastener allows for a user to access the area of an abrasive article nearer to centering ring 420. Backup pad 400 may have a total height 454.

Height 452 needs to be high enough to receive and maintain a position of an abrasive article. A backup pad 400 intended for use with a nonwoven may have a higher height 454, therefore, than one for use with a coated abrasive disc. Using a centering ring helps to keep an abrasive article centered on backup pad 400 during use, providing more holding power for a potentially higher maximum operating speed rating.

FIG. 4D illustrates a backup pad 460 with a Dual Lock™ hook and loop fastener in place, which receives an abrasive article, as illustrated in FIG. 4E where abrasive article 472. As illustrated by line 480 in FIG. 4E, abrasive article 472 is substantially coplanar with a top of centering ring 464.

While a retainer nut may fit within centering ring 464, it may be difficult to easily remove it with a spanner wrench if the height of centering ring 464 is consistent about the circumference.

While FIGS. 4A-4E illustrate backup pads where a centering ring and the backup pad face are one solid component, it is expressly contemplated that, in some embodiments, they are manufactured separately and coupled together, for example using a tongue and groove, adhesive or other suitable method. It is expressly contemplated, however, that in other embodiments they are made together, e.g. in the same mold but with separate material components. It may be advantageous to have two components, such that the centering ring can have different properties than the backup pad face. For example, it may be helpful, for some abrasive articles, to have a centering feature exhibit more flexibility, or to expand under rotational forces and lock the abrasive article into place so that it not only remains centered, but cannot slip rotationally either.

FIGS. 5A-5B illustrate a backup pad in accordance with some embodiment herein. Backup pad 500 includes a centering ring 510 on a backup pad face 502. While FIGS 5A- 5B illustrate a backup pad 500 where centering ring 510 and backup pad face 502 are a single component, it is expressly contemplated that they may be separate components made of the same, or different, material.

Centering ring 510 has a number of wave-like features, each with a maximum height 512 and minimum height 514. The minimum heights 514 provide space for a spanner wrench to access a retaining nut.

FIG. 5B illustrates a view 550 of a backup pad 550, with a Dual Lock ™ fastener 552 on the backup pad face next to a backup pad with an abrasive article 556 in place. Centering ring 554 is substantially coplanar with a top surface of abrasive article 554.

While FIG. 5 A illustrates a centering ring 510 with four wave-like features, it is expressly contemplated that other shapes and configurations are possible. For example, while minimum heights 514 are roughly equidistant from maximum heights 512, other configurations are possible so long as a spanner wrench can access a retaining nut. In fact, while FIG. 5A illustrates an even number of wave-like features, it may actually be preferable to have an odd number of features such as three features, five features, seven features, nine features or more. The features need to be smaller than a spanner wrench to be used, and need to have height variability to allow the wrench access.

FIGS. 5C-1 to 5C-3 illustrate another embodiment where a centering feature 580 moves independently of backup pad face 570. As illustrated clearly in FIG. 5C-3, centering feature 580 may be a separate component that fits within a recess 572 of backup pad face 570. As illustrated in FIG. 5C-1, one or more coupling components 582 may be present that allow for centering feature 580 to be inserted into, and not easily removed from, backup pad face 570. For example, one or more snaps, or a tongue and groove may be used. Other coupling mechanisms are also possible. It is expressly contemplated, however, that in some embodiments, centering feature 580 is removeable, either by undoing a locking feature or another mechanism.

FIG. 5C-1 illustrates a cutaway view that clearly illustrates component 580, and a potential direction of rotation 584. When a retaining nut is applied, in some embodiments, centering feature 584 is retained in position. However, as illustrated in FIG. 5C-2, an interior diameter of centering feature 586 may be larger than an interior diameter 574 of backup pad face 570, such that a retaining nut does not hinder movement of centering feature 580.

Allowing for centering feature 580 to rotate independently of backup pad face 570 may increase the ease of removing a backup pad from a tool. For example, in embodiments where waves or other features are narrow, rotating a spanner wrench may cause the spanner wrench to go over a wave crest, which could cause the spanner wrench to dislodge. In contrast, a spanner wrench can be placed between waves of centering feature 580, and centering feature 580 moves with the spanner wrench as it rotates, making it easier to remove the backup pad. FIGS. 6A-6C illustrate profiles of a centering feature for a backup pad in accordance with some embodiments herein. While FIGS. 5A-5B illustrate a centering ring with wave-like features that gently slope up to a maximum height and down to a minimum height, it is expressly contemplated that other designs are possible. FIGS. 6A-6C illustrate some other options of centering feature profiles that may be suitable for some embodiments. Profiles 600, 630 and 650 may be connected end-to-end to form a centering feature, such that a length of profiles 600, 630, and 650 become a perimeter of a centering feature.

Profile 600 has a plurality of rectangular protrusions 602, each with a width 608, spaced apart by one another by spacing 606. In contrast, profile 630 illustrates a plurality of square protrusions 632, each with a width 638, spaced apart from adjacent protrusions by spacing 636. Profile 650 illustrates a number of protrusions 652, each with a base length 658, spaced apart by spacing 656. However, while squares, rectangles and triangles are illustrated, it is expressly contemplated that other shapes are contemplated. For example: hemispheres, elliptical portions, right triangles, obtuse triangles, isosceles triangles, acute triangles, regular polygons, irregular polygons or other shapes. Spacing between adjacent protrusions may be greater, or smaller, than the width of protrusions themselves. FIGS. 6D-6F illustrate top-down views of backup pads 660, 670 and 680, each with a centering feature 664, 674, 684. As illustrated, centering features may be, but do not have to be, concentric rings with a perimeter of backup pad 664. A centering feature have any perimeter as long as balance is maintained as the backup pad rotates. Non-circular shapes may provide ease of access to a retaining nut without the need to add wave or other features as illustrated in FIGS. 6A-6C.

FIG. 6D illustrates a backup pad 660 with a backup pad face 662. A centering feature 664 protrudes from backup pad face 662. Centering feature 664 is triangular in shape. Backup pad 660 couples to a tool drive shaft using aperture 666, which may include threading or an X-lock or other attachment feature.

FIG. 6E illustrates a backup pad 670 with a backup pad face 672. A centering feature 674 protrudes from the backup pad face 672 in the shape of a square. A shaft coupling feature 676 is present on backup pad 670.

FIG. 6F illustrates a backup pad 680 with a backup pad face 682. Centering feature 674 protrudes from backup pad face 682 in the shape of an oval. A shaft coupling feature 686 is present on backup pad 680.

While FIGS. 6D-6F illustrate a triangular, square and oval centering feature, it is expressly contemplated that other shapes are possible. For example, other polygonal shapes such as rectangles, pentagons, hexagons, heptagons, octagons, nonagons, etc. Additionally, other shapes may be possible such as stars, crescents, tears, or any other suitable shape.

Described herein thus far are centering features that are immovably molded or adhered to a backup pad face, a centering feature of the backup pad is shaped for easy access of the spanner wrench to the retainer nut. In some embodiments, the centering feature is also mobile relative to the rest of the backup pad such that an access point in the centering feature moves along with the spanner wrench when removing the nut.

FIG. 7 illustrates a method of removing a backup pad from a tool in accordance with embodiments herein. Method 700 may be useful for removing backup pads herein from a tool.

In block 710, if present, a locking mechanism is unlocked.

In block 720, the retainer nut is loosened, using the spanner wrench. For example, the retainer nut may be coupled to a tool shaft by threading. Loosening may include twisting the retaining nut along the threads. The spanner wrench may help keep the tool shaft from spinning.

In some embodiments, a centering feature of the backup pad is shaped for easy access of the spanner wrench to the retainer nut. In some embodiments, the centering feature is also mobile relative to the rest of the backup pad such that an access point in the centering feature moves along with the spanner wrench when removing the nut.

In block 730, the retainer nut is removed.

In block 740, the backup pad is loosened, if needed. In some embodiments, the retainer nut is the only feature maintaining the position of the backup pad on the tool.

In block 750, the backup pad is removed.

FIG. 8 illustrates a method of centering an abrasive article on a backup pad in accordance with embodiments herein. Method 800 may be useful for swapping out a new backup pad and / or new abrasive article.

In block 810, a backup pad is placed. For example, a tool shaft receiving hole of the backup pad is placed over the tool shaft.

In block 820, the backup pad is secured in place. For example, a retaining nut 822 may be placed within a centering ring of the backup pad and secured using a spanner wrench. Alternatively, or additionally, a flange 824 may be placed between the retaining nut, or another fastener, and the backup pad. Threading 826 may be present between the backup pad and a tool shaft. Other suitable fastening mechanisms 828 are also expressly contemplated. The backup pad should be secured in place to ensure that it does not spin off the tool during use. It is therefore key that the centering ring not impede the ability of a spanner wrench, or other tightening element, to securely fasten the backup pad to a tool shaft.

In block 830, the abrasive article is placed on the backup pad.

In block 840, the abrasive article is aligned about the centering ring such that an inner circumference of the abrasive article is outside of an outer circumference of the centering ring.

In block 850, the abrasive article is secured in place, using a Dual Lock ™ hook and loop system, an adhesive, or another suitable system for coupling the abrasive article to the backup pad. In block 860, a visual check is done to ensure that the abrasive article is correctly placed and held fast.

FIG. 9 illustrates a block diagram of a backup pad in accordance with embodiments herein. Backup pad 900 may be similar to other backup pad embodiments described herein. However, backup pad 900 should not be considered limited by other backup pad embodiments illustrated herein.

Backup pad 900 includes a backup pad face 920. Backup pad face 920 is a planar surface that receives an abrasive article with an abrasive article engaging feature 922, such as a Dual Lock ™ hook and loop fastener, an adhesive - either a permanent adhesive or a pressure sensitive adhesive, such as Stikit™ or another suitable fastener that holds an abrasive article in contact with the backup pad face920. Backup pad face 920 is made of a material with features 924 selected for a given operation. For example, backup pad face 920 can be flexible and soft, or rigid and hard. Backup pad face 920 can be made of any number of plastic polymers, copolymers or mixtures thereof. Backup pad face 920 can also include other features 928.

Backup pad 900 also includes a tool engaging feature 930 that couples backup pad 900 to a tool shaft, such as threading or a retaining nut. Tool engaging feature 930 needs to keep backup pad 900 coupled to tool during use, with minimal slippage.

Backup pad 900 also has a centering ring 950. Centering ring 950 has a profile 970 that extends upward from backup pad face 920. Centering ring 950 may be perpendicular to backup pad face 920, or angled from backup pad face 920. Profile 970 may be a flat profile, or may have a shape 972 that varies along the circumference of ring 950. Shape 972 may include waves, peaks, valleys, steps up or down, or any other suitable shape 972. Profile 970 may have a minimum height 976 and a maximum height 974 at different points along profile 970. In some embodiments, there is an odd number of maximum heights 974, such as three, five, seven, nine, or eleven maxima. Maximum height 974 may be spaced apart equally along profile 970, to keep from creating a weight imbalance. Profile 970 may also have other features 978.

Centering ring 950 is composed of a material with material feature 952. Centering ring material 952 may be different than material 924. For example, it may be beneficial for centering ring 950 to have more flexibility and expansion properties to better maintain a position of an abrasive article on backup pad face 920 during use. Centering ring 950 may also have other features.

FIGS. 10A-10C illustrate different backup pads being attached to a power tool. FIG. 10A illustrates a conventional backup pad assembly 1000. FIG. 10B illustrates a backup pad assembly 1100 with a centering ring. FIG. 10C illustrates a backup pad assembly 1200 with a centering ring having wave features.

FIG. 10A-1 illustrates a backup pad 1010 engaged with a threaded shaft 1012 of a power tool. In the transition from FIG. 10A- 1 to FIG. 1 OA-2, a retaining nut 1020 is engaged to shaft 1012. Retaining nut 1020 fits partially within a depression of backup pad 1010. Retaining nut 1020 has receiving apertures 1022 for a spanner wrench 1030 that, in FIG. 10A-3, engages and tightens retaining nut 1020 into place. However, as discussed above, the reduced area of contact between backup pad 1010 and an abrasive article increases a potential for the abrasive article to slip along the surface of backup pad 1010.

FIG. 10B-1 illustrates a backup pad 1110, with a centering ring 1140, that engages a threaded shaft 1112 of a power tool. In the transition from FIG. 10B-1 to 10B-2, a retaining nut 1120 is engaged to shaft 1112. Retaining nut 1120 fits tightly within backup pad 1110, which can make it difficult to remove. Retaining nut 1120 has receiving apertures 1122 for a spanner wrench 1130 that, in FIG. 10B-3, engages and tightens retaining nut 1120 into place. However, as illustrated, spanner wrench 1130 contacts a surface of centering ring 1140, which can make it difficult to maneuver and sufficiently tighten nut 1120.

FIG. 10C-1 illustrates a backup pad 1210 with a centering ring 1240, that engages a threaded shaft 1212 of a power tool. In the transition from FIG. 10C-1 to 10C-2, a retaining nut 1220 is engaged to shaft 1212. Retaining nut 1220 fits within centering ring 1240, but with some space between an edge of retaining nut 1220 and centering ring 1240, which allows for easier removal. Retaining nut 1220 has apertures 1222 which receive a spanner wrench 1230. As illustrated in FIG. 10C-3, it is easier for the spanner wrench 1230 to access retaining nut 1220 because of the troughs in between the wave features. However, the presence of the wave crests help to keep an abrasive article centered on backup pad 1210.

Components of backup pads and abrasive disc mounting assemblies, as described herein, should be made of appropriately durable materials. Examples include engineering plastics (e.g., nylons, polyphenylene sulfide, polyether ketone, polyether ether ketone, polycarbonate, high density polyethylene, high density polypropylene), polymer composites, metals, ceramic composites, and combinations thereof. However, backup pads may also be formed of metal, wood or ceramic, depending on an application.

In practice of methods according to the present disclosure, repositioning of the abrasive disc relative to the raised proj ection of the back-up pad may be repeated any desired number of times. The methods may be practiced manually, automatically, robotically, or a combination thereof.

The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

WHAT IS CLAIMED IS:

1. An abrasive article mounting assembly comprising: a backup pad comprising: a tool engaging aperture that receives a shaft of a tool; an backup pad face; a centering feature that maintains a position of an abrasive article on the backup pad face, wherein the centering feature protrudes from the backup pad face; and a fastener that couples the backup pad to the shaft.

2. The assembly of claim 1, wherein the centering feature protrudes at an angle from the backup pad face.

3. The assembly of claim 1 , wherein the centering feature has an exterior perimeter that engages an interior perimeter of the abrasive article.

4. The assembly of claim 3, wherein the centering feature has a polygonal shape.

5. The assembly of claim 3, wherein the centering feature comprises a constant height about the perimeter.

6. The assembly of claim 3, wherein the centering feature comprises a maximum height and a minimum height, wherein the minimum height is less than the maximum height.

7. The assembly of claim 6, wherein the maximum height is a feature height of a feature, and wherein the feature repeats about the circumference.

8. The assembly of claim 7, wherein the feature repeats an odd number of times about the circumference.

9. The assembly of claim 7, wherein the feature repeats an even number of times about the circumference.

10. The assembly of claim 1, wherein the centering feature comprises a first material, and the backup pad face comprises a second material different from the first material.

11. The assembly of claim 1, wherein the backup pad face comprises a removeable coupling mechanism that receives the abrasive article.

12. The assembly of claim 1, wherein the backup pad comprises nylon, polyethylene, polypropylene, polyurethane, thermoplastic polyurethane, thermoplastic polyethylene, or any copolymer thereof.

13. The assembly of claim 1, wherein the fastener is a retaining nut.

14. The assembly of claim 1, wherein the backup pad has a depression that receives the fastener.

15. The assembly of claim 1, wherein the centering feature moves independently of the backup pad face.

16. A backup pad for an abrasive article, the backup pad comprising: a backup pad face; a centering feature, extending from the backup pad face, wherein the centering feature has an inner perimeter and an outer perimeter; and wherein the backup pad face receives an abrasive article such that an article inner perimeter fits about the outer perimeter.

17. The backup pad of claim 16, wherein the backup pad face comprises a fastener that releasably couples to an abrasive article.

18. The backup pad of claim 16, wherein the centering feature is a centering ring and wherein the inner perimeter is sized to receive a retaining nut.

19. The backup pad of claim 16, wherein the centering feature has a repeating feature.

20. The backup pad of claim 16, wherein the repeating feature has a minimum height and a maximum height.

21. The backup pad of claim 20, wherein the repeating feature repeats three times.

22. The backup pad of claim 16, wherein the backup pad face comprises a first material, and the centering feature comprises a second material that is different from the first material.

23. The backup pad of claim 22, wherein the second material has a different molecular weight from the first material.

24. The backup pad of claim 22, wherein the second material has a different hardness from the first material.

25. The backup pad of claim 22, wherein one of the first and second materials comprises a filler material.

26. The backup pad of claim 22, wherein the first material is more rigid than the second material.

27. The backup pad of claim 16, wherein the centering feature is compressible.

28. The backup pad of claim 16, and further comprising: a depression within the inner circumference.

29. The backup pad of claim 28, wherein the depression is sized to receive a fastener that fastens the backup pad to a tool.

30. The backup pad of claim 16, wherein the centering feature moves independently of the backup pad face.

31. A method of exchanging a first backup pad for a second backup pad, the method comprising: loosening a connection between the first backup pad and a tool; removing a fastener from the first backup pad, wherein the fastener is within a first centering feature of the first backup pad; removing the first backup pad from the tool; placing the second backup pad on the tool; coupling the fastener to the second backup pad by placing the fastener within a second centering feature of the second backup pad; and securing the fastener to the tool.

32. The method of claim 31, wherein the fastener is a retaining nut, and wherein the second centering feature is shaped to allow a spanner wrench to engage and tighten the retaining nut.

33. The method of claim 32, where, when the spanner wrench rotates the retaining nut, the second centering feature rotates with the spanner wrench.

34. The method of claim 31, wherein the second centering feature has a profile with a repeating shape, with a taller portion and a shorter portion, and wherein the shorter portion receives the spanner wrench.

35. The method of claim 31, wherein the second backup pad comprises a depression that receives the retainer nut such that, when secured, the retainer nut has a lower profile than the second centering feature.

36. The method of claim 31 , wherein the second centering feature has an outer perimeter sized to receive an interior perimeter of an abrasive article.

37. The method of claim 31, wherein the second centering feature comprises a compressible material.

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38. The method of claim 31, wherein the second centering feature comprises a flexible material.

39. The method of claim 31, wherein the second centering feature comprises a more flexible material than the second backup pad.

40. The method of claim 31, wherein removing comprises engaging the fastener with a tool, and wherein, as the tool rotates, the first centering feature rotates independently of a backup pad face.

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