Bench Grinders Safety. Bench grinder tool rest
US20020086629A1. Conversion attachment for bench grinder tool rest. Google Patents
Publication number US20020086629A1 US20020086629A1 US09/750,808 US75080800A US2002086629A1 US 20020086629 A1 US20020086629 A1 US 20020086629A1 US 75080800 A US75080800 A US 75080800A US 2002086629 A1 US2002086629 A1 US 2002086629A1 Authority US United States Prior art keywords attachment tool rest tool receiving plate flange Prior art date 2000-12-28 Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Granted Application number US09/750,808 Other versions US6722968B2 ( en Inventor Nanette Rizzo David Hollinger Charles Baird Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Orion International Original Assignee Orion International Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) 2000-12-28 Filing date 2000-12-28 Publication date 2002-07-04 2000-12-28 Application filed by Orion International filed Critical Orion International 2000-12-28 Priority to US09/750,808 priority Critical patent/US6722968B2/en 2001-03-21 Assigned to ORION INTERNATIONAL reassignment ORION INTERNATIONAL ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAIRD, CHARLES, HOLLINGER, DAVID, RIZZO, NANETTE 2002-07-04 Publication of US20020086629A1 publication Critical patent/US20020086629A1/en 2004-04-20 Application granted granted Critical 2004-04-20 Publication of US6722968B2 publication Critical patent/US6722968B2/en 2020-12-28 Anticipated expiration legal-status Critical Status Expired. Lifetime legal-status Critical Current
- 238000006243 chemical reaction Methods 0.000 title description 4
- 239000000789 fastener Substances 0.000 claims abstract description 24
- 230000036633 rest Effects 0.000 claims abstract description 7
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 241001270131 Agaricus moelleri Species 0.000 claims description 2
- 239000004033 plastic Substances 0.000 claims description 2
- 229920003023 plastic Polymers 0.000 claims description 2
- 239000002023 wood Substances 0.000 claims description 2
- 230000000284 resting Effects 0.000 claims 2
- 230000000875 corresponding Effects 0.000 claims 1
- 238000005520 cutting process Methods 0.000 description 11
- 239000000463 material Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000005498 polishing Methods 0.000 description 3
- 102100000672 SMPX Human genes 0.000 description 2
- 108060007673 SMPX Proteins 0.000 description 2
- 230000000153 supplemental Effects 0.000 description 2
- 241000755266 Kathetostoma giganteum Species 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000023298 conjugation with cellular fusion Effects 0.000 description 1
- 238000004512 die casting Methods 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 230000001771 impaired Effects 0.000 description 1
- 230000002045 lasting Effects 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 230000021037 unidirectional conjugation Effects 0.000 description 1
- B — PERFORMING OPERATIONS; TRANSPORTING
- B24 — GRINDING; POLISHING
- B24B — MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B27/00 — Other grinding machines or devices
- B24B27/02 — Bench grinders
An attachment for a bench grinder having at least one grinding surface, a tool rest fastener and a tool rest is described. The attachment includes a tool-receiving plate having a bottom surface and a top surface. The bottom surface is configured to matingly engage the tool rest surface. The top surface includes one of a flat surface and a surface having an angled V-shaped groove that is shaped and configured to receive a drill bit or and hold it at a fixed elevation and angle relative to the grinding surface. A slotted flange is normally attached to the tool-receiving plate, is configured to engage the slot with the tool rest fastener while the tool-receiving plate rests on the tool rest surface, and to abut the flange against the attachment surface to hold the attachment immobile during use.
This invention is directed to an improved attachment for a bench grinder to hold drill bits or other tools in preparation for sharpening. specifically, it relates to attachments to temporarily convert a flat tool support into a tool support for sharpening drill bits, or for converting a tool rest for drill bits into a flat tool support. 
Tools commonly used for cutting, such as chisels, gouges, planes, knives and lawn mower blades, have cutting surfaces that do not function properly if not kept sharp and free of surface imperfections. Dull blades require application of more force to the tool in order to cut a workpiece, potentially cutting too deeply or posing a safety hazard. Surface imperfections in such tools can impart defects in the cut surface of the workpiece, particularly during woodworking. A chisel or planer with a gouge in the cutting surface will leave an imperfection on a workpiece that requires additional sanding or finishing to obtain an acceptable surface appearance. 
Drill bits also become dull with use, and it is advantageous to be able to use a grinder to restore the cutting edge to its original quality. For optimum sharpness, the tip of a drill bit cannot simply be held flat against a grinding surface. The tip of the drill bit forms a cone whose sides slope at an angle of 118° from the sides of the drill bit. Maintenance of the optimum cutting surface requires that the conical shape be retained as much as possible. It is therefore necessary that the bit be held to the grinding surface at a 62° angle as precisely as possible. In addition, the bit should be continuously rotated to minimize formation of flat areas on the cone. 
Bench grinders are commonly used in the home to sharpen tools with cutting edges that have become nicked, dull or worn. The grinder sharpens or repairs the cutting edge of such tools by wearing away a small portion of the metal until a sharp, flawless edge is achieved. An accessory commonly used with bench grinders is a tool rest or tool support that supports the tool at an appropriate height so that it can more easily be sharpened. A commonly used tool rest consists of a flat surface that is either permanently or removeably attached to the grinder. Without any tool rest, it is extremely difficult, even for an experienced workman, to hold a drill bit at precisely 62° while rotating it for the length of time needed to sharpen the bit. 
Even where the tool support surface can be tilted to various angles, in most cases, adjustment of the surface angle must be accomplished entirely by hand, setting up to four elements to lock the tool rest at a selected angle and elevation. Setting the proper elements and holding the round bit in the same position for consistent results is very difficult under these conditions. 
recently, grinders have become available with a permanently attached tool rest specifically designed with a V-shaped channel to hold drill bits in an appropriate position for sharpening. The groove is generally oriented to hold the drill bit at an angle of approximately 62°, characteristic of the shape of the cutting tip of the bit. However, use of this type of tool rest is not advantageous for use when sharpening many other types of cutting surfaces. For example, a chisel may be placed on the tool rest with a portion of the blade on the flat area of the tool rest and a portion of the blade over the V-shaped channel. A downward force on the blade during sharpening could cause the blade to shift into the V-shaped channel changing its angular orientation, wearing away the edge at an inappropriate angle and causing damage to a portion of the blade. 
Further, the groove that holds drill bits at a characteristic angle of 62° is not useful for other small items that may require sharpening. Removal of a nick or gouge in the blade of a flat head screwdriver, for example, would not benefit from this type of tool support, since the angle does not hold the screwdriver in a position appropriate for grinding. 
Since no single tool rest optimally sharpens all types of tools, there exists a need for attachments for permanently mounted tool rests to convert easily and inexpensively from one type to another. 
It is, therefore, an object of this invention to provide an improved attachment that adapts a tool rest to hold either flat tools or drill bits in an optimum position for sharpening. 
It is another object of this invention to provide an improved drill bit sharpening attachment that mounts on a bench grinder without removal of an existing flat tool rest. 
It is still another object of this invention to provide an improved adapter for converting a tool rest to a flat surface, without removal of a grooved tool rest for sharpening drill bits. 
It is yet another object of this invention to provide an improved drill bit sharpening attachment that is easily removed, providing convenient access to a permanently installed flat tool rest. 
The above-listed objects are met or exceeded by the present tool rest attachment, which features a removable platform for converting a flat tool rest to one specially designed to sharpen drill bits, or vice versa. 
specifically, the present invention provides an attachment for sharpening of either a tool or a drill bit with a bench grinder. The attachment is designed to be used on a grinder having at least one grinding surface and a tool rest that is attached with a tool rest fastener. The tool rest has a tool rest surface and attachment surface at right angles to each other. 
The attachment has a tool-receiving plate with a bottom surface and a top surface. The bottom surface is shaped and configured to matingly engage the tool rest surface. The top surface comprises one of a flat surface and a surface having an angled V-shaped groove that is shaped and configured to receive a drill bit and hold it at a fixed elevation and angle relative to the grinding surface. If the top surface is flat, it is designed to support a tool at a fixed height relative to the grinding surface. 
A slotted flange is normally attached to the tool-receiving plate. It is sized and configured to engage the slot with the tool rest fastener. While the tool-receiving plate rests on the tool rest surface, it abuts the flange against the attachment surface when the tool rest fastener is tightened, to hold the attachment immobile during use. 
During use, the attachment acts as an adapter to convert a flat tool rest to one useful for sharpening drill bits or adapts a grooved tool rest to one with a flat support surface. Single tool rests that attempt to provide the versatility to accomplish both of these tasks, generally require many manual settings to change the height and angle of the tool rest. The attachment of the present invention permits conversion from one type of tool rest to another, without removal of the permanently mounted tool rest. 
This attachment is very simple to use. When the different surface is required, the user need only loosen the fastener, drop the attachment into place and tighten the fastener again. In seconds, a sturdy, secure surface is available for grinding of either drill bits or other tools. 
Removal of the attachment, and return to the original tool rest surface is equally simple. The user need only loosen the fastener, remove the attachment, and retighten the fastener in its original position. There is no need to replace the permanently mounted tool rest. Further, this attachment is easy and inexpensive to manufacture. 
This attachment provides an additional advantage when sharpening drill bits. The groove in the attachment is designed to hold the bit in the exact optimum position of 62°. Compared to manually setting angles and positions on the tool rest, this method is more accurate and consistent, leading to sharper bits. Less grinding, and therefore less metal removal, is required to obtain a good edge, resulting in longer lasting tools. 
FIG. 1 is a perspective view of a bench grinder with the conversion attachment installed thereon; 
FIG. 6 is a side elevational view of the attachment shown in FIG. 2 as viewed along line  6-6 and in the direction indicated;
FIG. 7 is a side elevational view of the attachment shown in FIG. 2 as viewed along line  7-7 and in the direction indicated; and
FIG. 8 is an exploded, perspective view of the present attachment and a preferred mounting assembly. 
Referring to FIG. 1, an attachment, generally designated  10, is shown that is used for sharpening a tool or drill bit (not shown), with a bench grinder, generally designated 14. The grinder 14 with which the attachment 10 is intended to be used must have at least one wheel surface 16, a tool rest 18, and a tool rest fastener 20 that secures the tool rest to a base 22 of the grinder. Generally, the tool rest 18 has a tool rest surface 24 and an attachment surface 26. Most often these surfaces 24, 26 will be oriented at right angles to each other, however, other angles may be used.
Although a grinding  surface 17 is the most commonly used as the wheel surface 16, and is referenced here, it is to be understood that this invention is applicable to any type of wheel that is available for use with a bench grinder 14. In addition to grinders 17, other wheels that are offered include those with wire bristles or polishing surfaces. After sharpening a tool, a wire brush is preferably used to remove metal filings, or a polishing wheel used to put a finer edge on the tool. These steps are particularly convenient when they can all be done right at the bench grinder 14 simply by changing the wheel or moving to an additional wheel surface 16.
The  tool rest surface 24 is most often flat. Alternately, an attachment 10′ could be made to convert a tool rest 18 with a grooved surface to a flat-surface tool rest. If there were sufficient demand for such an item, a similar attachment could be made to matingly engage with and rest upon a tool rest surface 24 of any shape. Two embodiments are described. In the first embodiment, best shown in FIG. 2, the tool rest surface 24 is flat, and is being converted to a grooved surface for use in sharpening drill bits. The attachment 10′ is used to convert a grooved tool rest surface 24 to a flat surface in a second embodiment, shown in FIG. 3.
Referring now to FIG. 2, a tool-receiving  plate 30 is the working surface of the attachment 10. The tool-receiving plate 30 has a bottom surface 32 and a top surface 34. A forward edge 36 closest to the wheel surface 16 has a length, L1, and a rear edge 38 opposite the forward edge 36 has a length L2. The top surface 34 is where, during use, drill bits or other tools are placed for support during grinding. The overall length, L1, and width, W1, of the tool-receiving plate must be sufficient to provide a work surface that is large enough to be useful, but small enough that access to the grinding surface by larger items is not impaired. Most preferably, the length, L1, is from about 1.0 to about 2.5 times the width, W1.
The width, W  1, of the tool-receiving plate 30 is particularly important in the first embodiment. When sharpening drill bits, it is most advantageous to continuously rotate the bit. Placement of the bit during sharpening in one position too long causes flat spots on the tip of the bit. It is therefore important that the user be able to grasp the bit in order to turn it. Thus, it is preferable that the width, W1, of the tool-receiving plate 30, not exceed the length of the smallest drill bit that the user intends to sharpen. It is therefore preferred that W1 not exceed 50 mm, and even more preferred that W1 be less than 45 mm.
The  bottom surface 32, as shown on FIGS. 2, 3 and 4 of the tool-receiving plate 30 is shaped and configured to matingly engage the tool rest surface 24 of the tool rest 18. For the purposes of this invention, the bottom surface 32 and the tool rest surface 24 are considered to be matingly engaged if the surfaces are planar as well as non-planar. Referring first to FIGS. 2 and 4, in the embodiment 10, when the tool rest surface 24 is substantially flat, the bottom surface 32 will be correspondingly flat. However, referring now to FIG. 3, in an alternate embodiment, generally designated 10′, if the tool rest surface 24 has any other shape, the bottom surface 32 must be configured with an inverse shape so that, when placed together, the bottom surface 32 of the attachment 10′ conforms to the shape of the tool rest surface 24 to provide a stable platform for the tool-receiving plate 30. Aside from the construction of the bottom surface 32′, the embodiment 10′ is virtually identical to the attachment 10, and has been designated with like reference numbers. For ease of discussion, while the main FOCUS will be on the attachment 10, it will be understood that the description also applies to the attachment 10′.
In the  second embodiment 10′, the tool rest surface 24 has a shaped or non-planar surface, and the bottom surface 32′ is preferably shaped to matingly engage with the tool rest surface. As shown in FIG. 3, the bottom surface of this embodiment includes a depending, V-shaped projection 42 that preferably has generally the same angle and dimension, similar in configuration and orientation to a V-shaped groove 40, as discussed further below. Thus, when the attachment 10′ is placed on top of the tool rest 18, the projection 42 fits within the groove 40. Further, such mating engagement of the tool rest 18 with the attachment 10′ acts as a locking mechanism against lateral movement of the attachment during use. Thus, it is contemplated that the attachment 10, 10′ will either have a grooved top surface 34 and a flat bottom surface 32, or a flat top surface 34′ and a bottom surface 32′ with the projection 42.
The  top surface 34, 34′ is the surface that is configured to support drill bits, or other tools of interest, during sharpening or grinding. Usually, the overall shape and dimensions of the top surface 34, 34′ will be the same as that of the bottom surface 32′, although shapes with sloped sides or changing dimensions are contemplated for use with this invention. In the second embodiment, the top surface 34′ of the attachment 10′ is substantially flat.
Referring back to FIG. 2, in the first embodiment, to provide convenient support for drill bits, the angled V-shaped  groove 40 in the tool-receiving plate 30 is oriented and configured to receive the drill bit and hold it at a fixed elevation and angle relative to the grinding surface 17. To hold the tip of the drill bit at the optimum angle, the groove 40 is placed at an angle, α, of from about 59° to about 65°. Optimally, α is 62°, the supplemental angle to the shape of the drill bit tip, 118°. Preferably, α, is from about 60° to about 64°, and most preferably from 61° to 63°. The groove 40 preferably runs the entire width of the attachment 10, from the forward edge 36 to the rear edge 38, so that the user can grasp the bit to rotate it while sharpening. As discussed here, the angles are measured from the forward edge 36, based on an assumption that the forward edge 36 is parallel to the grinding surface 17. Where the forward edge 36 is at any other orientation, a should be measured with respect to the grinding surface 17.
As shown in FIG. 5, the position of the groove along the length L  1, of the top surface 34 preferably changes to fit the specific bench grinder 14 with which the attachment 10 is intended to be used. L3 defines the distance along the forward edge 36 between the center of the V-shaped groove 40 and a common edge 48 between the tool-receiving plate 30 and a slotted flange 50. Preferably this forward edge 36 is parallel to the grinding surface 17 of the wheel 16. L3 should be chosen to place the tip of the drill bit near the right side of the grinding wheel 16.
Size and thickness of the V-shaped  groove 40 may vary as long as the drill bits are held securely within it, as shown in FIGS. 5 and 6. The groove 40 must be wide enough that large drill bits do not slip out of the groove. In the preferred embodiment, the V-shaped groove 40 is symmetrical, having equal slope on both sides 51 of the “V”. However, it is contemplated that either side 51 may be at a steeper angle than the other.
Preferably, the thickness or height ‘H’ (FIG. 6) is such that the  attachment 10 does not bend easily and provides a sturdy working surface, particularly in the center of the V-shaped groove 40. If the groove 40 has insufficient depth, the bits will move on the tool-receiving plate 30 as if it were flat. Preferably, the depth of the V-shaped groove 40 is from about ½ to ¾ of the overall thickness H of the tool-receiving plate 30. The overall thickness H of the tool-receiving plate 30 depends on the material from which it is made. However, excessive thickness requires additional raw materials that are not utilized, increasing the cost of the product unnecessarily. While the attachment is made of die cast aluminum, the overall thickness is preferably from about 5 mm to about 15 mm.
A trapezoid is the preferred shape of the  surfaces 32, 34, on the tool-receiving plate 30 although any shape may be used that provides sufficient surface to grind or sharpen the desired tools. A free edge 52 is on the opposite side of the tool-receiving plate 30 from the common edge 48. As shown, L2 is preferably less than L1, such as the case where the free edge 52 of the tool-receiving plate 30 is formed to be parallel to the V-shaped groove 40. This provides a sufficient surface area for the intended use, but minimizes cost by eliminating raw materials for excess surface that is unlikely to be used.
Except as noted above, other overall dimensions of the tool-receiving  plate 30 are variable. Size and placement of the tool rest 18 varies depending on the manufacturer or model of the bench grinder 14. Changes in dimensions of the attachment 10 to fit specific models of the tool-receiving plate of bench grinder 14 are intended to be within the scope of this invention.
Size and shape of the slotted  flange 50 is variable as discussed above so long as it engages the tool rest fastener 20 and the attachment 10, 10′ matingly engages the tool rest surface 24. As few as two tines 53 extend from the tool-receiving plate 30 to the tool rest fastener 20, or as many as desired for a specific grinder configuration. The preferred shape includes a substantially flat plate, most preferably having a length, from the common edge 28 to the end of the tines 53, which is approximately equal to the width W1. When there is a large contact surface between the slotted flange 50 and the attachment surface 26 of the tool rest 18, increased friction reduces movement between the surfaces, making the contact between the two apparatuses more stable. Preferably, angled edges 54, 56 on the slotted flange 50 minimize use of the raw material used to manufacture the attachment 10, thus minimizing the cost without impairing the usefulness of the device.
The slotted  flange 50 normally attaches to the tool-receiving plate 30 at the common edge 48, and is preferably integrally joined thereto. It is important that the plate 30 remain stationary while in use. Movement of the plate 30 during a polishing or grinding action may lead to an uneven edge being formed, or inadvertent nicking or chipping of the cutting surface. The slotted flange 50 and tool-receiving plate 30 may be joined by any means, but preferably form an L-shaped device of unitary construction.
A preferred mounting assembly is shown in FIG. 8. Attachment of the  tool rest 18 to the bench grinder 14 is usually accomplished by means of a removable tool rest fastener 20, which also engages a slot 58 on the slotted flange 50. The flange 50 is generally sized and configured to engage a slot 58 with the tool rest fastener 20 while the tool-receiving plate 30 is matingly engaged with the tool rest surface 24. When placed in this position, the flange 50 should abut the attachment surface 26 of the tool rest 18 to hold the attachment 10 immobile during use when the tool rest fastener 20 is tightened.
Optionally, a  washer 56 is used when fastening the attachment 10 to the tool rest 18. When suitable, the tool rest fastener 20 is fastened directly to the base 22 of the bench grinder 14, or it optionally attaches to a bracket 58. A supplemental fastener 60 is then used to mount the bracket 58 to the bench grinder base 22.
Referring now to FIG. 6, thickness of the slotted  flange 50 preferably diminishes at an angle β, from the common edge 48 to the slot 58. Less than 5% change in thickness is sufficient to aid in manufacture by aiding release of the attachment 10 when made in a mold. preferably, β is such that there is less than 3% change in thickness. Overall, the slotted flange 50 should be thick enough that it has the strength to hold the tool-receiving plate 30 in a secure position. Making the slotted flange 50 thicker than necessary adds to the cost of the raw materials, and merely increases the cost of the attachment 10.
The  attachment 10 is suitably manufactured from one of a variety of materials. Rigidity is the most important quality of the material from which the unit is made, to minimize movement during use. The material preferably has sufficient compression strength that it does not crack, break or deform when the user bears down on the drill bit or tool 14 to hold it in place. Since the tool rest 18 supports the tool-receiving plate 30, tensile strength is less important. Preferred materials include wood, metal, and rigid plastics. Rust-free metals, such as aluminum are most preferred. Die casting is the preferred method of manufacture.
While a particular embodiment of the conversion attachment for a bench grinder tool rest feature of the invention has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims. 
Claims ( 21 )
An attachment for sharpening one of a tool and a drill bit with a bench grinder having at least one grinding surface, a tool rest fastener and a tool rest, the tool rest having at least a tool rest surface and an attachment surface oriented at generally right angles to each other, comprising:
a tool-receiving plate having a bottom surface and a top surface, said bottom surface being configured to matingly engage the tool rest surface, said top surface comprising one of a substantially flat surface and a surface having an angled V-shaped groove that is configured to receive the drill bit and hold it at a fixed elevation and angle relative to the grinding surface; and
a slotted flange normally attached to said tool-receiving plate, configured to engage said slot with the tool rest fastener while said tool-receiving plate rests on the tool rest surface, and to abut said flange against the attachment surface when the tool rest fastener is tightened, to hold said attachment immobile during use.
Bench Grinders Safety
Bench grinders, which are sometimes referred to as offhand or pedestal grinders, are a common piece of equipment on job sites and in the shop. They are used for a variety of tasks, including sharpening, polishing, buffing and cleaning metal objects.
However, if used incorrectly, bench grinders can create a number of hazards. For instance, if the bench grinder is poorly maintained, the abrasive wheel may shatter, creating dangerous projectiles. What’s more, loose clothing and jewelry can become tangled in the bench grinder during use, which can cause serious injuries.
This article discusses Occupational Safety and Health Administration (OSHA) requirements for bench grinder safety and ways employees can stay safe on the job when using them.
Bench grinders are typically equipped with several types of guards, including tongue guards, work rests and side guards:
Tongue guards or spark arresters
Tongue guards are metal plates located at the upper part of the wheel opening of the bench grinder. These guards prevent pieces of the grinding wheel from harming nearby workers should the wheel shatter. Per OSHA, tongue guards should be adjusted to ensure there’s no more than a ¼-inch clearance between the guard itself and the grinding wheel.
Per OSHA, bench grinders must be equipped with a rest that can support workpieces. To prevent the workpiece from being jammed between the wheel and the rest, work rests must be adjusted in such a way that the gap between the face of the grinding wheel and work rest is no more than ⅛ of an inch.
Sometimes referred to as spindle guards, these guards are designed to enclose the wheel and spindle of a bench grinder. Per OSHA, side guards must cover the spindle and no less than 75% of the wheel.
Additional Safety Considerations
While machine guarding is critical when it comes to bench grinder safety, there are additional precautions to keep in mind:
- The grinder is to be securely anchored to prevent walking or moving.
- Make sure the wheel you are using is compatible with the bench grinder. If the wheel isn’t rated for the grinder, it could break and create serious injury risks.
- Perform a ring test before mounting a new wheel. These tests involve tapping the wheel with a nonmetallic object. If, during the test, you hear a dull, thud-like sound, the wheel may be damaged.
- Avoid standing directly in front of a bench grinder as you turn it on. If the wheel is damaged in any way, it may shatter as it gets up to speed.
- Wear the proper personal protective equipment when operating a bench grinder. This can include the following:
- Face shields
- Safety glasses
- Hearing protection
- Leather or canvas work gloves
Keeping in mind these precautions can go a long way toward ensuring your safety whenever you use a bench grinder. For more information, speak with your supervisor.
This blog and its contents are not intended to be exhaustive nor should any discussion or opinions be construed as legal advice. Readers should contact legal counsel for legal advice. Extracted from Zywave’s article “Safety Matters – Bench Grinders Safety Alert 2022″ © 2010, 2014, 2019 Zywave, Inc. All rights reserved.
A bench grinder is probably not a tool you’ll use every day. However, if it’s available and set up correctly, you’ll be surprised how often it comes in handy for everything from sharpening tools to rounding over thread ends on a cutoff bolt. We’ve assembled these tips to help you get the most out of your grinder.
Keep a Container of Water Handy
Most chisels and other cutting tools are made of tempered steel. If the steel gets too hot and turns bluish black, it’s overheated and won’t hold an edge very long. To avoid ruining the edge of a tool by overheating, keep water nearby to cool the tool. A good technique is to move the tool once across the bench grinder for no more than a few seconds. Then dip it in the water. If the steel edge does overheat and turns color, grind the edge back to good steel and start over.
Grind Small Objects Safely
Hold small objects with locking pliers. This keeps your fingers a safe distance from the grinding wheel and protects them against burns from the hot metal. It also gives you better control over the grinding process.
Make Tool Sharpening Guides
Here’s a better way to hold tools securely while you’re grinding them—and take the guesswork out of creating the right bevel angle. It’s a short piece of 2×4 with an angled end and a 1-1/4-in. hole for a clamp. I made one for sharpening chisels and plane blades, and a few more with different angles for wood-turning tools. Large labels with the tool’s name tell you which blocks are for which tools. For a Delta grinder with a 6-in.-diameter wheel, a 5-1/2-in.-long piece of 2×4 aligns the tool to the wheel just right. For other bench grinders, you may need to adjust this length. Note: The angle you cut on the block is not the same as the tool’s bevel angle. But let’s skip the math. To determine the block angle, turn off the grinder and hold the tool’s bevel flush against the wheel. The angle of the tool shaft to the workbench is the angle to cut on the 2×4. Our thanks to Ray Caputo for this sharp accessory.
Consider a Low-Speed Grinder for Sharpening
Unless they’re variable speed, most bench grinders run at about 3,450 rpm. If you’re careful and keep the wheel dressed (more on that in another tip), these high-speed grinders work fine. But for sharpening garden and other tools, a low-speed grinder running at 1,750 rpm is a better choice. The lower speed reduces the chance you’ll overheat the edge of your tool. Another advantage of a low-speed grinder (100 to 150) is that this type typically includes friable white grinder wheels, which do a better job of sharpening than the gray grinder wheels usually included with high-speed grinders. See how to use an angle grinder.
Dress Wheels Frequently
Wheel dressing squares the face of the wheel, but more important, it exposes new grit for more efficient cutting. As a wheel is used, the spaces between the cutting grit can become clogged, and the grit itself dulled. A wheel in this condition can cause overheating and slows material removal. A wheel dresser like the one shown here (15 to 30) has a bar with diamond grit impregnated in it. Holding the bar against the spinning wheel cuts away the surface to expose new grit, squares the face of the wheel and rounds the wheel. To use a dressing tool like this, start the bench grinder and wait for it to reach full speed. Then press the diamond wheel dresser against the spinning wheel, holding it perpendicular to the face of the wheel. Be sure to wear a good-quality dust mask. The fine aluminum oxide dust is very bad for your lungs. Draw a pencil line on the wheel before you start to help you gauge when you’ve removed enough material from the wheel. Dress the wheel just until the pencil line disappears.
Watch for the Sparks to Come Over the Top
When you’re sharpening a chisel or other tool, you can tell when the edge is getting sharp by watching the sparks. When the edge is blunt, the sparks are deflected downward. But as the edge gets sharper, the sparks roll over the tool and cascade down the surface facing you. When you see this start to happen, be careful about grinding much more because a thin edge is very vulnerable to overheating.
Make an Angle Gauge
Chisels and other cutting tools work best if their edges are ground at the correct angle. You can search online to find the optimal angle for whatever tool you’re sharpening. Most wood chisels should be ground to about a 25-degree angle with a secondary micro-bevel angle of 30 degrees on the tip of the blade. An angle gauge allows you to set the tool rest at the desired angle. You can make an angle gauge from a thin piece of cardboard using an inexpensive protractor. 1. MARK THE ANGLE ON CARDBOARD Align the center mark on the protractor with the top edge of the cardboard. Then turn the protractor until the desired angle is also aligned with the top edge. Draw a line along the protractor to mark the angle. Don’t forget to label the angle. Cut along the line to create the gauge. 2. ADJUST THE TOOL REST Set the cardboard on the tool rest and adjust the angle of the tool rest until the wheel contacts the center of the angled portion of the cardboard gauge.
Upgrade the Tool Rest
Inexpensive bench grinders have tool rests that are finicky and difficult to adjust. If you do a lot of tool sharpening or simply want a bench grinder tool rest that’s easier to adjust, consider adding a stand-alone tool rest. There are several variations, some made for specific tasks like sharpening lathe turning tools. This Veritas model has two adjustments for positioning and aligning the tool rest, and levers for easy tightening. You can also buy an attachment that holds chisels or plane irons.
Make Your Grinder Portable
Even the most nicely organized home workshops don’t have enough bench space to devote a section to a bench grinder. A good solution is to mount your grinder to a board or small stand so you can clamp it to the bench when you need it, and store on the shelf when you don’t. The compartment on this grinder stand is a good spot to keep your dressing tool and safety glasses so they’re handy when you need them. For a fancier version, build a little drawer to fit the space under the grinder. The stand is built from two 12 x 16-in. pieces of 3/4-in. plywood separated by two 4 x 12-in. uprights. We used two 5/16-in. bolts with washers and nuts to attach the grinder, leaving enough space in front of the grinder to mount a stand-alone tool rest.
Easy-to-Clamp Mobile Base
Shazam! Fasten your bench-top tools to your workbench in seconds. Bolt 3/4-in. plywood bases on the tools and then glue and screw a wood strip along the front edge to fit into a woodworking vise. Crank this strip into a vise to lock the tool into place. If you don’t have a vise, drill a couple of clearance holes along the face of the wood strip on the base and drive screws through the strip into the edge of your workbench. Then just unscrew to remove the tool.
Set Up a Polishing Station
A bench grinder fitted with a wire wheel on one side and a cotton buffing wheel on the other side, or buffing wheels on both sides, makes a great cleaning and polishing tool. You’ll also need a set of polishing compound sticks (14). Polishing compound sticks are color coded to indicate the grit, from coarse to very fine. To use the polishing wheel, hold the stick against the buffing wheel as it spins to transfer some polishing compound to the wheel. Then hold the object lightly against the wheel and let the compound polish the surface.
Sharpen Your Lawn Mower Blade
Sharpening your lawn mower blade is easy with a bench grinder. Grind the tapered cutting edges with a grinder only if you see nicks in the blade. Follow the factory angle of the cutting edge. The grinder will remove nicks in the blade much faster than you can file them.
Not All Grinding Wheels are the Same
You can use two kinds of aluminum-oxide wheels to sharpen your chisels; one is blue-gray and the other white. We used the darker-color wheel, which is harder and will keep its shape longer. The drawback, however, is that it grinds hotter than the softer, white wheel. Too much heat will weaken the steel. The soft wheel will need more frequent shaping with a dressing tool, but you’ll be less likely to burn the edge of your chisel while grinding. For best results, use a 100-grit wheel to shape your chisel blades.
Know When to Replace a Wheel
Slide the wheel over your finger and tap the wheel in four places with a screwdriver handle. All taps should sound the same. If they don’t, scrap the wheel. It’s cracked.