Abrasive wheel machine guarding

Under 1910.215(a)(1) abrasive wheels may be used without the safety guards only in three narrow situations: wheels used for internal work while inside the workpiece, mounted portable wheels 2 inches or smaller in diameter, and certain cones/plugs/ threaded‑hole pot balls when the work itself provides protection. See 1910.215(a)(1) and its exceptions at 1910.215(a)(1)(i), 1910.215(a)(1)(ii), and 1910.215(a)(1)(iii).

• These exceptions are limited and must be applied exactly as written.
• If the wheel does not meet one of these exceptions, it must be used on a machine provided with the safety guards required by the section.

Under 1910.215(a)(2) the safety guard must cover the spindle end, nut, and flange projections unless a specific exception applies that permits exposing them when the work itself provides protection or the machine is a portable saw. See 1910.215(a)(2) and the exceptions at 1910.215(a)(2)(i) and 1910.215(a)(2)(ii).

• If the nature of the work entirely covers the side of the wheel, side covers may be omitted under [1910.215(a)(2)(i)].
• Portable saws may have the spindle end, nut, and outer flange exposed under [1910.215(a)(2)(ii)].
• Guards must still be mounted and fastened so alignment is maintained and fastening strength exceeds guard strength per the same paragraph.

Under 1910.215(a)(4) offhand grinding machines must have rigid, adjustable work rests kept within 1/8 inch of the wheel and securely clamped after each adjustment; adjustments must not be made while the wheel is in motion. See 1910.215(a)(4).

• Work rests must be adjustable to compensate for wheel wear and designed to support the workpiece.
• Maximum opening between rest and wheel is one‑eighth inch (0.125"), and the rest must be firmly clamped after adjustment.
• Never adjust the work rest while the wheel is turning.

Under 1910.215(b)(2) guard openings must be measured without counting visors or accessory equipment as part of the guard unless that equipment has strength equal to the guard. See 1910.215(b)(2).

• When checking compliance with the maximum allowed exposure angles in paragraphs (b)(3)–(8), do not include visors or accessories unless they are as strong as the guard itself.
• This ensures the guard alone provides the rated protection specified in those paragraphs.

Under 1910.215(b)(3) safety guards on bench and floor stand grinders must limit angular exposure to not more than 90° (one‑fourth of the wheel periphery), beginning at a point no more than 65° above the horizontal plane of the wheel spindle. See 1910.215(b)(3).

• If the work requires contact below the horizontal plane, the exposure may be increased up to 125° as allowed in the same paragraph.
• Refer to the figures (O‑6 through O‑9) in the standard for visual guidance on measuring angles.

Under 1910.215(b)(4) safety guards for cylindrical grinding machines shall not expose more than 180° of the wheel periphery and sides, and that exposure must begin at a point not more than 65° above the horizontal plane of the wheel spindle. See 1910.215(b)(4).

• The standard also references figures (O‑10 and O‑11) and paragraph (b)(9) for requirements on adjustability to compensate for wheel wear.
• Guards must be adjustable so the specified maximum angular exposure is never exceeded as the wheel diameter decreases.

Under 1910.215(b)(5) the maximum angular exposure for cutting‑off wheels and surface grinders that use the wheel periphery is 150°, and this exposure must begin at a point not less than 15° below the horizontal plane of the wheel spindle. See 1910.215(b)(5).

• Consult Figures O‑12 and O‑13 in the standard to measure and verify the exposure angle.
• Ensure guards are constructed and positioned so the exposure does not exceed this limit.

Under 1910.215(b)(8) where the work is applied above the horizontal centerline (top grinding), the exposure of the grinding wheel periphery must be as small as possible and must not exceed 60°. See 1910.215(b)(8).

• Top grinding is considered higher risk because pieces can be thrown upward, so guards must minimize exposure.
• Use the figures (O‑16 and O‑17) for visual guidance on acceptable openings.

Under 1910.215(b)(9) guards where the operator stands in front of the opening must allow the peripheral protecting member to be adjusted to the wheel's decreasing diameter so the maximum angular exposure above horizontal is never exceeded and the distance between the wheel periphery and the adjustable tongue or end of the peripheral member at the top never exceeds one‑fourth inch. See 1910.215(b)(9).

• The adjustable peripheral member (e.g., an adjustable tongue) must be kept within 1/4 inch of the wheel periphery as the wheel wears down.
• Regular adjustment and inspection are required to maintain this clearance and the prescribed exposure angle.

Under 1910.215(b)(10)(i)–(iii) guard material and minimum thickness requirements are specified by the figures and tables in the standard: cast iron or malleable iron or equivalent guards for speeds up to 8,000 surface feet per minute, and cast steel or structural steel guards for wheel speeds over 8,000 up to 16,000 surface feet per minute. See 1910.215(b)(10)(ii) and 1910.215(b)(10)(iii).

• Use Figures O‑36/O‑37 and Table O‑9 for minimum basic thicknesses by guard type and service class per 1910.215(b)(10)(i).
• Select guard materials appropriate to the operating surface speed of the wheel to ensure adequate containment in case of failure.

Under 1910.215(b)(1)(iii) revolving cup guards for cup wheels must be made of steel or other material of adequate strength, enclose the wheel sides upward from the back for one‑third of the wheel thickness, conform with all mounting requirements of the section, and maintain a clearance between the wheel side and guard not exceeding one‑sixteenth inch. See 1910.215(b)(1)(iii).

• The guard must mount behind the wheel and rotate with it (revolving type).
• Clearance to the wheel side must not exceed 1/16 inch to prevent dangerous movement yet allow free rotation.

Under 1910.215(b)(11) band‑type guards must be continuous steel plate or material of equal strength, have ends riveted/bolted/welded to leave the inside free of projections, have an inside diameter no more than 1 inch larger than the wheel outside diameter, and be mounted as nearly concentric with the wheel as practicable. See 1910.215(b)(11), 1910.215(b)(11)(i), 1910.215(b)(11)(ii), and 1910.215(b)(11)(iii).

• The band must be wide enough and positioned so the wheel does not protrude beyond the band edge more than allowed in Figure O‑29 and Table O‑2 (or wall thickness W), per [1910.215(b)(11)(iii)].
• Continuous construction with smooth inside avoids snagging and reduces failure risk.

Under 1910.215(b)(12) abrasive wheel machinery guards must meet the design specifications of the American National Standard Safety Code for the Use, Care, and Protection of Abrasive Wheels, ANSI B7.1‑1970, which the regulation incorporates by reference via [1910.6]. See 1910.215(b)(12) and 1910.6.

• Employers should use ANSI B7.1 design criteria for guard construction details not fully specified in the OSHA text.
• The incorporation by reference means compliance with the ANSI provisions is required for covered guards (except for natural sandstone or certain abrasive discs noted in the paragraph).

Under 1910.215(c)(1) abrasive wheels must be mounted between flanges that are at least one‑third the wheel diameter, except for many listed exceptions such as mounted wheels, portable wheels with threaded inserts or projecting studs, certain discs, plate mounted wheels, cup/cylinder/segmental wheels mounted in chucks, Types 27/28 wheels, certain internal wheels, modified Types 6 and 11, and cutting‑off wheels (Types 1 and 27A) which have different flange rules. See 1910.215(c)(1) and the exceptions at 1910.215(c)(1)(i)(a)–(i)(i).

• For typical wheels the flanges must be at least one‑third the wheel diameter.
• Review the specific exceptions in the paragraph because several common wheel types have tailored flange requirements.

Under 1910.215(c)(1)(ii) Type 1 cutting‑off wheels must be mounted between properly relieved flanges with matching bearing surfaces that are at least one‑fourth the wheel diameter; under 1910.215(c)(1)(iii) Type 27A cutting‑off wheels may be mounted by flat (not relieved) matching flanges that may be less than one‑third but not less than one‑fourth the wheel diameter. See 1910.215(c)(1)(ii) and 1910.215(c)(1)(iii).

• Type 1: relieved flanges with matching bearing surfaces, minimum 1/4 diameter.
• Type 27A: flat flanges with matching bearing surfaces, minimum 1/4 diameter and may be between 1/4 and 1/3 diameter.

Under 1910.215(a)(3) and (c) flanges are required to mount abrasive wheels safely and must meet dimensional and mounting requirements (including the minimum flange sizes and exceptions) to ensure the wheel is properly supported and runs true. See 1910.215(a)(3) and 1910.215(c)(1).

• Proper flange design prevents uneven loading and reduces risk of wheel breakage.
• Follow the detailed flange sizing and exception rules in paragraph (c) to match the wheel type in use.

Under 1910.215(b)(1)(ii)–(iii) cup wheels may be protected by either band‑type guards described in paragraph (b)(11) or by special revolving cup guards that mount behind the wheel, are strong enough (steel or equivalent), enclose the wheel sides upward from the back for one‑third wheel thickness, and maintain a clearance not exceeding 1/16 inch. See 1910.215(b)(1)(ii) and 1910.215(b)(1)(iii).

• Choose band‑type guards that comply with the general band specifications in 1910.215(b)(11).
• Ensure whichever guard is used meets the mounting, clearance, and material strength requirements of the standard.

Under 1910.215(b)(3) and 1910.215(b)(4), with the adjustment rules spelled out in 1910.215(b)(9), the distance between the wheel periphery and the adjustable tongue or end of the peripheral member at the top must never exceed one‑fourth inch. See 1910.215(b)(9).

• Maintain this ≤1/4" gap by routine adjustment as the wheel wears to keep operator exposure within the angular limits.
• Document inspection/adjustment frequency in your maintenance procedures to ensure compliance.

Under 1910.215(b)(10)(v) cutting‑off wheels larger than 16 inches diameter and operating at speeds not exceeding 14,200 surface feet per minute must use the safety guards specified in Figures O‑27 and O‑28 and in Table O‑1 of the standard. See 1910.215(b)(10)(v).

• Follow the referenced figures and table for guard dimensions and construction details appropriate to those large cutting‑off wheels.
• Confirm guard material and thickness per the tables for the wheel service and speed.

Under 1910.215(b)(3) if the work requires contact below the horizontal plane, bench and floor stand grinder guards may allow angular exposure up to 125°. See 1910.215(b)(3).

• This is a specific allowance for certain work needs; however, the guard must still meet adjustability and clearance requirements in [1910.215(b)(9)].
• Always minimize exposure consistent with the task and the guard design.

Under 1910.215(b)(6) and (b)(7) guards for swing frame grinders and automatic snagging machines must limit angular exposure to no more than 180°, and the top half of the wheel must be enclosed at all times. See 1910.215(b)(6) and 1910.215(b)(7).

• Enclosing the top half prevents thrown fragments or workpieces from being ejected upward toward the operator.
• Ensure guard mounting and strength conform to the material and thickness requirements in paragraph (b)(10).

Under 1910.215(b)(11)(ii) the inside diameter of a band‑type guard shall not be more than 1 inch larger than the outside diameter of the wheel and must be mounted as nearly concentric with the wheel as practicable to prevent excessive wheel protrusion and uneven containment. See 1910.215(b)(11)(ii).

• A tight fit (≤1" clearance) reduces the chance the wheel will shift or protrude beyond the band during operation.
• Concentric mounting minimizes eccentric loading, vibration, and potential guard failure.

Under 1910.215(b)(11)(iii) the band must be sufficiently wide and positioned so the wheel never protrudes beyond the band edge more than the distance shown in Figure O‑29 and Table O‑2 or the wall thickness (W), whichever is smaller. See 1910.215(b)(11)(iii).

• Check Figure O‑29 and Table O‑2 to determine the maximum allowable protrusion for your wheel size and type.
• Periodically inspect and adjust band position to ensure compliance especially when changing wheel sizes or after maintenance.

Under 1910.215(b)(10)(vi) thread grinding wheels not exceeding 1 inch in thickness must use cast iron or malleable iron safety guards as specified in Figures O‑36 and O‑37 and in Table O‑9. See 1910.215(b)(10)(vi).

• Consult Figures O‑36/O‑37 and Table O‑9 for minimum thickness and dimensional requirements for these guards.
• Select guard construction consistent with wheel service class to ensure containment.

Under 1910.215(a)(2)(i) the spindle end, nut, and outer flange may be exposed on operations where the work itself provides suitable protection to the operator, and where the work entirely covers the side of the wheel the side covers may be omitted; however the employer must ensure the work truly provides that protection and that overall guarding requirements are met. See 1910.215(a)(2)(i).

• Employers must evaluate whether the nature of the work reliably shields operators from wheel fragments and contact hazards.
• Do not assume the exception applies; document the basis for using the exception and periodically verify conditions remain protective.

Under 1910.215(a)(1)(ii) mounted wheels used in portable operations that are 2 inches or smaller in diameter are exempt from the safety guard requirement; larger portable wheels must be used with guards. See 1910.215(a)(1)(ii).

• Confirm the wheel diameter is 2" or less to rely on this exception.
• When using larger portable mounted wheels, provide the required safety guards per the standard.

Under 1910.215(b)(1)(i) cup wheel safety guards must comply with the guard specifications in paragraphs (b)(1) through (b)(10) of the section, which include material, clearance, exposure angle, and adjustability requirements tailored to cup wheels. See 1910.215(b)(1)(i).

• In practice you must follow the band‑type guard specs in 1910.215(b)(11) or the revolving cup guard requirements in 1910.215(b)(1)(iii).
• Inspect cup wheel guards for the specific clearances (1/16" where required) and mounting strength per the section.

Under 1910.215(d)(1) you must inspect and "ring" the wheel before mounting, and you should remove any wheel that gives a dead (cracked) sound. To perform the ring test, tap the dry wheel gently with a nonmetallic implement (handle of a screwdriver or wooden mallet), about 1–2 inches from the periphery and about 45° each side of the vertical centerline, then rotate 45° and repeat; a clear metallic tone means the wheel is not cracked and may be mounted.

• Follow the steps in 1910.215(d)(1) and the detailed tapping guidance in 1910.215(d)(1)(ii).
• Make sure wheels are dry and free of sawdust because wet or dirty wheels deaden the sound (1910.215(d)(1)(i)).
• If the wheel sounds dead or cracked, do not use it.

Under 1910.215(d)(2) and 1910.215(d)(3) you must ensure the wheel fits freely on the spindle (a controlled clearance) and all contact surfaces are flat and free of foreign matter.

• The spindle should be made to nominal size plus zero minus 0.002 inch so the wheel hole is suitably oversize to allow safety clearance during heat and pressure changes (1910.215(d)(2)).
• Make sure the bearing/contact surfaces of the wheel, blotters, and flanges are flat and clean (1910.215(d)(3)).
• Remove dirt, rust, or burrs that could cause uneven bearing or excessive flange pressure.

Under 1910.215(c)(6)(i) blotters must generally be used between flanges and abrasive wheel surfaces to distribute flange pressure uniformly, but 1910.215(d)(5) lists specific wheel types that do not require blotters.

• Use blotters (compressible washers) between flanges and wheel surfaces to ensure even pressure as required by 1910.215(c)(6)(i).
• Blotters are not required for several exceptions listed in 1910.215(d)(5), including mounted wheels, abrasive discs with inserted nuts or studs, plate mounted wheels, cylinders/cups mounted in chucks, Types 27 and 28 wheels, certain cutting-off wheels, certain internal wheels, Type 4 tapered wheels, many diamond wheels, and modified terrazzo wheels (see 1910.215(d)(5)(i)-(ix)).
• When blotters are required, they must cover the entire contact area of the wheel flanges (1910.215(d)(5)).

Under 1910.215(c)(4)(ii) and 1910.215(c)(1)(v) Type 27 and Type 28 wheels require specially designed adaptors and must always be used with a safety guard between the wheel and the operator.

• The back flange for Type 27/28 wheels must extend beyond the hub and contact the wheel to counteract side pressure as required by 1910.215(c)(4)(ii).
• Regardless of flange type, the wheel shall always be guarded and blotters used per 1910.215(c)(1)(v).
• Note: 1910.215(c)(4)(ii) also states mounts affixed by the manufacturer must not be reused and Type 27/28 wheels shall be used only with a safety guard located between wheel and operator.

Under 1910.215(c)(1)(iv)(a)-(c) three general flange types are allowed—straight relieved, straight unrelieved, and adaptor flanges—and regardless of flange type the wheel must always be guarded.

• The three flange types are listed in 1910.215(c)(1)(iv): straight relieved flanges (1910.215(c)(1)(iv)(a)), straight unrelieved flanges (1910.215(c)(1)(iv)(b)), and adaptor flanges (1910.215(c)(1)(iv)(c)).
• In every case, the wheel must be guarded and blotters used in accordance with 1910.215(c)(1)(v).

Under 1910.215(c)(5)(i)-(ii) straight relieved flanges must have a recess of at least 1/16 inch next to the wheel for the distance specified in Table O-6, and adaptor or sleeve type flanges must be undercut so there is no bearing on the wheel sides within 1/8 inch of the arbor hole.

• Straight relieved flanges must be recessed at least 1/16 inch on the side next to the wheel as set out in 1910.215(c)(5)(i).
• Straight adaptor or sleeve flanges must be undercut to avoid bearing on the wheel sides within 1/8 inch of the arbor hole per 1910.215(c)(5)(ii).
• Follow the dimensions shown in the referenced tables and figures for compliance.

Under 1910.215(c)(3) and 1910.215(c)(9) flanges must be dimensionally accurate, balanced, free of rough surfaces or sharp edges, and maintained in good condition—reface or replace flanges that are worn, warped, sprung, or damaged.

• Ensure flanges are dimensionally accurate and in good balance with no rough surfaces or sharp edges per 1910.215(c)(3).
• When bearing surfaces become worn or damaged, true or reface them, maintaining proper relief and rigidity as required by 1910.215(c)(9); replace when they no longer conform to the specification tables and figures.
• Damaged flanges can cause excessive flange pressure around the wheel hole and increase risk of wheel failure.

Under 1910.215(c)(8)(i)-(iii) you must use the specified tables and figures (Tables O-4, O-5, O-6, O-7, O-8 and Figures O-30–O-35) to select flanges that meet the minimum dimensions required for the wheel and spindle or adaptor configuration.

• For small-hole wheels that fit directly on the spindle, follow the minimum dimensions in 1910.215(c)(8)(i) (Tables O-4 and O-6; Figures O-30 and O-32).
• For wheels with holes larger than the spindle, use the adaptor flange dimensions in 1910.215(c)(8)(ii) (Table O-5, Table O-7, Figures O-31, O-33, O-34).
• For straight flanges integral to wheel sleeves on precision grinders, follow 1910.215(c)(8)(iii) (Table O-8; Figure O-35).
• Dimensions shall never be less than those indicated in the tables/figures.

Under 1910.215(c)(7) and 1910.215(d)(6) when more than one wheel is mounted between a single set of flanges, you may cement wheels together or separate them with spacers that equal the flange diameter and bearing surface; use wheels manufactured for multiple mounting when spacers are not used.

• The driving flange must be securely fastened and run true (1910.215(c)(7)).
• Multiple wheels may be cemented together or separated by specially designed spacers equal in diameter to the mounting flanges with equal bearing surfaces as required in 1910.215(d)(6).
• If using multiple uncemented wheels without spacers, use wheels specifically manufactured for that purpose to avoid unsafe loading.

Under 1910.215(d)(4) a bushing used in the wheel hole must not exceed the width of the wheel and must not contact the flanges.

• Ensure the bushing is no wider than the wheel and that it does not extend to touch the flanges per 1910.215(d)(4).
• Improperly sized or positioned bushings can create uneven bearing and excessive flange pressure, increasing wheel failure risk.

Under 1910.215(c)(6)(ii) and 1910.215(d)(5) the standard lists several exceptions where blotters are not required, including mounted wheels, certain abrasive discs, plate-mounted wheels, cylinders/cups mounted in chucks, Types 27 and 28 wheels, certain cutting-off wheels, certain internal wheels, Type 4 tapered wheels, most diamond wheels, and modified terrazzo wheels.

• See the exceptions enumerated in 1910.215(c)(6)(ii)(a)-(j) and the parallel list in 1910.215(d)(5)(i)-(ix).
• Confirm your wheel type against those exception subparagraphs before omitting blotters.

Under 1910.215(d)(1)(ii) you should tap the wheel about 45° each side of the vertical centerline and about 1–2 inches from the periphery, then rotate the wheel 45° and repeat the taps.

• The standard describes these tap points and rotation sequence in 1910.215(d)(1)(ii).
• Tapping at these spots and repeating after rotating helps detect cracks that may not be audible at a single point.

Under 1910.215(d)(1) you must check the machine spindle speed before mounting to make sure it does not exceed the wheel's marked maximum operating speed.

• Verify the wheel's maximum RPM marking and compare it to the machine spindle speed; do not mount a wheel if spindle speed exceeds the wheel's marked maximum (1910.215(d)(1)).
• If necessary, consult the machine's tachometer or nameplate, or run the machine at reduced speed per manufacturer guidance to match the wheel rating.

Under 1910.215(c)(4)(iii) modified Types 6 and 11 (terrazzo) wheels with a tapered K dimension are recognized by the standard and require the special dimensional considerations shown in the referenced figures and tables.

• Follow the modified wheel dimensional guidance in 1910.215(c)(4)(iii) and the applicable tables/figures for proper mounting and flange compatibility.
• Use adaptor designs and blotter applications described elsewhere in 1910.215 when applicable.

Under 1910.215(c)(1)(v) wheels must always be guarded regardless of flange type, and under 1910.215(c)(6)(i) blotters should be used between flanges and wheel surfaces to ensure uniform flange pressure unless the wheel type is an exception.

• Always provide a safety guard between the wheel and operator as required by 1910.215(c)(1)(v).
• Use blotters per 1910.215(c)(6)(i), and consult 1910.215(c)(6)(ii) for exceptions where blotters are not required.

Under 1910.215(d)(6) and 1910.215(c)(7) when mounting multiple wheels between a single set of flanges you may cement the wheels together or use spacers that are equal in diameter and bearing surface to the mounting flanges; ensure the driving flange is securely fastened and runs true.

• If cementing wheels together is used, ensure the wheels are manufactured and marked for that purpose and the assembly is balanced (1910.215(c)(7)).
• If using spacers, they must match flange diameter and bearing surface per 1910.215(d)(6).
• Avoid mixing wheels not intended for multiple mounting unless specifically manufactured for that use.

Under 1910.215(d)(5) when blotters or compressible flange facings are required they must cover the entire contact area of the wheel flanges.

• Ensure blotters fully cover the flange contact surface as specified in 1910.215(d)(5).
• Partial blotter coverage can create uneven pressure and increase the risk of wheel damage.

Use the minimum band material, thickness, rivet diameter, and rivet spacing shown in Table O-3 for band-type guards at speeds up to 7,000 surface feet per minute (SFPM). See 1910.215(d)(6) for the table.

• For example, hot-rolled steel (SAE 1008) for wheels under 8 inches requires at least 1/16 inch band thickness, 3/16 inch rivets, and a maximum 3/4 inch distance between rivet centers.
• For wheels 8 to 24 inches, Table O-3 increases the minimum band thickness to 1/8 inch, rivet diameter to 1/4 inch, and rivet spacing to 1 inch.

Follow the exact sizes in Table O-3 to ensure the guard will withstand wheel forces and avoid replacing a prescriptive requirement with a weaker design. See 1910.215(d)(6).

Use the minimum B, D, E and F dimensions shown in Table O-5 for organic bonded wheels over 1 1/2 inches thick; those dimensions depend on wheel diameter and bore size. See 1910.215(d) and Table O-5.

• The table gives recommended combinations of wheel hole (bore) diameter (B), flange outside diameter (D), flange thickness at bore (E), flange thickness at edge of undercut (F), and the minimum F (D–E) for wheel diameters (for example, for 12–14 in. wheels, B = 4–6 in., D = 7–8 in., E = 7/8 in., F = 3/8 in., minimum F thickness 1/2 in.).
• Note the footnote: for wheels under 1 1/4 inches thick the F dimension shall not exceed 40 percent of wheel thickness.

Match the exact row that corresponds to your wheel diameter and bore size from Table O-5 to ensure the wheel/flange assembly meets the standard in 1910.215(d).

Straight relieved flanges must meet the minimum dimensions in Table O-6 when used on wheels with the relieved-flange design; the table lists B, C (radial width), and D/E thicknesses by flange diameter. See 1910.215(d) and Table O-6.

• Table O-6 provides the minimum outside diameter of flanges (B), radial width of bearing surface (C), and minimum flange thickness at bore (D) and at edge of recess (E) for flange sizes (A) 1 through 72 (these sizes correspond to common wheel/flange assemblies).
• Footnote: "Flanges for wheels under 2 inches diameter may be unrelieved and shall be maintained flat and true." That means very small wheels can be unrelieved, but must be flat and true instead of using a relieved flange.

Always choose the flange size row that matches your wheel/flange diameter and follow the dimensions in Table O-6 so your flange assembly complies with 1910.215(d).

For mechanical grinders operating between 12,500 and 16,500 SFPM, use the minimum flange dimensions and material notes in Table O-7 and its footnotes. See 1910.215(d) and Table O-7.

• Table O-7 lists minimum bore (B), flange outside diameter (D), flange thickness at bore and at edge of undercut, and the minimum F (D–E) for specific wheel diameters used on mechanical grinders at these higher speeds (for example, a 20-inch wheel may require B = 6–8 in., D = 8–10 in., D/E thicknesses of 1 to 1-1/2 in., etc., depending on the bore chosen).
• Footnote (1) requires flanges to be steel, quality SAE 1040 or equivalent, annealed and heat treated to an R value specified in the table preamble; Footnote (2) repeats the rule that for wheels under 1 1/4 inches thick the F dimension shall not exceed 40% of wheel thickness.

Follow the exact row and footnote requirements in Table O-7 so the flange and flange material are appropriate for the higher peripheral speeds required by 1910.215(d).

Select the minimum basic thickness from Table O-9 based on the guard material, maximum thickness of the grinding wheel, wheel diameter, and the applicable SFPM range; Table O-9 lists A (peripheral) and B (side) member thicknesses for each material and wheel size. See 1910.215(d)(6) and Table O-9.

• Example entries: for "materials satisfactory for speeds up to 8,000 SFPM" and a wheel 3–6 inches, A = 1/4 in. and B = 1/4 in.; for wheels over 12 to 16 inches A = 1/2 in. and B = 3/8 in. (values vary by material class and maximum wheel diameter).
• Table O-9 separates materials (cast iron, malleable iron, steel castings, structural steel, etc.) and gives progressively larger minimum thicknesses for larger wheels and higher speed ranges (e.g., up to 9,000 SFPM and up to 16,000 SFPM sections).

Use the exact material category and wheel diameter row in Table O-9 to determine the minimum A and B thicknesses so the safety guard meets 1910.215(d)(6).

Yes — straight flanges used as wheel sleeves for precision grinding may be used and may be clamped together by a central nut, bolts, or equivalent fastenings, subject to the minimum dimensions in Table O-8. See 1910.215(d) and Table O-8.

• Table O-8 provides minimum B (outside flange), D (thickness at bore), and E (thickness at edge of undercut) dimensions for wheel sleeves used only for precision grinding; the table also notes acceptable fastening methods.
• Note: for hole sizes smaller than those shown in Table O-8, the standard directs you to use Table 12 (referenced in the note to Table O-8) to determine proper dimensions and fittings.

Follow the exact flange sleeve dimensions and fastening methods in Table O-8 so the sleeve conforms to the requirements in 1910.215(d).