Safe handling and preventing accidents
It is said that “accidents happen when a person forgets.”
KGW produces abrasive products with safety in consideration under strict quality control. Products which pass careful inspections are packed in ways that will allow them to be safely delivered to the customers. Thereafter, these grinding wheels will not break as long as the precautions for handling, mounting, and use are observed.
Because most accidents occur when risk prevention is neglected, operators must also pay careful attention to safety and accident prevention.
1. Basic precautions concerning grinding wheels
(1) The strength of a grinding wheel (vitrified) is lower than that of glass or porcelain.
Therefore care must be taken to prevent damage to grinding wheels during shipping, transport, and other handling.
Because grinding wheels appear to be extremely strong, there is a tendency to accidently treat them roughly. However because they are significantly more fragile than glass or porcelain, they must be handled with complete care.
| Tensile strength (kg/cm²) | Elongation (%) | |
|---|---|---|
| Grinding wheel (vitrified) | 24 ～ 140 | 0.02 |
| Porcelain | 240 ～ 260 | （0.05 ～ 0.08） |
| Glass | 340 ～ 850 | 0.05 |
If a grinding wheel is fallen over, bumped against something, or dropped, it may be cracked and then broken during operation.
Do not roll grinding wheels on the floor. If it is unavoidable to roll it, put shock-absorbing materials, such as rubber sheets, Do not roll grinding wheels on the floor. If it is unavoidable to roll it, put shock-absorbing materials, such as rubber sheets, and boards on the floor.
(2) Grinding wheels should be stored in a dry area at room temperature. The racks, bins, or drawers should be constructed so that each of the various types of wheels can be stored in an orderly and safe manner.
Grinding wheels should be stored in a dry area in rooms not subject to extremely temperature changes. Thin wheels, such as those used for cutting off, should be laid flat on a flat structure of steel or similarly rigid material away from excessive heat, moisture, and other liquids to prevent warpage. Particular caution is required with organic bonded wheels and magnesia grinding wheels because they absorb moist and lose strength when exposed to humidity. Examples of storage methods are shown in Table 9-1.
(3) Use suitable grade grinding wheel at suitable pressure since too hard grade grinding wheel causes loading and glazing and then generates excessive heat, which may contribute to breakage.
Too hard grade grinding wheel causes loading and grazing and needs excessive pressure, and generates excessive grinding heat.
Grinding wheel at uniformed temperature is relatively safe even at high temperature (in particular dry grinding).
Temperature differences of 60-70℃ may cause wheel breakage.
Therefore, use softer grade grinding wheel (suitable grit size, grade, and structure) at suitable grinding pressure.
(4) Grinding wheel with softer grade and coarser grit size tends to be strength. Please pay attention in handling, storage, and use of grinding wheel.
When a grinding wheel is mounted, tighten the screws at suitable torque.
Observe the maximum operating speed without impact on the wheel during grinding operation.
(5) Do not force a grinding wheel with a small hole onto the machine spindle. If the hole diameter doesn’t fit the machine, please contact us.
And if the hole diameter is required to be altered, please request us for altering the hole diameter.
Forcing the grinding wheel with a small hole onto the machine spindle may cause the wheel breakage.
If the fit between the hole and the spindle is too tight, it may cause cracks of the wheel caused by the non-uniform tightening of the flange,
or thermal expansion of the spindle.
As a result, sudden accidents will occur.
Table 9-1: Limit deviations of hole
| Hole diameter | |||||
|---|---|---|---|---|---|
| Mechanically guided grinding | High-pressure grinding | Cutting-off, deburring, and fettling / snagging | |||
| （H） | Limit deviations (1) | （H） | Limit deviations (1) | （H） | Limit deviations (1) |
| 1.6 ≤ H ≤ 50 | +0.16 0 | 152.4 ≤ H < 203.2 | +0.46 +0.21 | H < 50.8 | +0.30 +0.10 |
| 50 < H ≤ 80 | +0.19 0 | 203.2 ≤ H ≤ 304.8 | +0.55 +0.26 | 50.8 ≤ H | +0.40 +0.10 |
| 80 < H ≤ 180 | +0.25 0 | 304.8 < H | +0.65 +0.33 | ||
| 180 < H ≤ 250 | +0.29 0 | ||||
| 250 < H ≤ 315 | +0.32 0 | Note (1) Applies when the accuracy for pilot diameter of the fixed-sideflange or the machine spindle diameter is f7 or tighter. | |||
| 315 < H ≤ 400 | +0.36 0 | ||||
| 400 < H ≤ 500 | +0.40 0 | ||||
| 500 < H | +0.44 | ||||
(6) Do not use the sides of straight wheel. If the sides are to be used, use other types of grinding wheels,
such as cup wheels, dish wheels, and wheels tapered on one side.
Using the sides of a straight grinding wheel is extremely dangerous. If the sides will be used, use a grinding wheel for sides.
(7) Grinding wheel discard size
Straight wheel discard size:
1/10 of extend wheel diameter from mounting flanges
Recessed wheel discard size:
1/5 of wheel thickness from the inside recess area.
(8) The grinding wheel operating speed must be at or below the maximum operating speed marked on the wheel and the inspection sheet.
For safety reasons, the maximum operating speed must be observed. Do not exceed this maximum operating speed at any time.
The maximum operating speed is the maximum peripheral speed at which the grinding wheel can be safely used.
It is indicated in unit of meters per second (m/s).
The maximum operating speed depends on the types of wheels.
The standard maximum operating speeds for types of wheels is given in Table 9-2. 
Table 9-2:Standard maximum operating speeds for types of wheels
| Types of wheels | Standard maximum operating speed | |||
|---|---|---|---|---|
| Inorganic bonds | Organic bonds | |||
Straight wheels | Non-reinforced | All other types | 33 | 50 |
| High-pressure grinding wheels | － | 63 | ||
| Thread and flute grinding wheels | 63 | 63 | ||
| Crankshaft and camshaft grinding wheels | 45 | 50 | ||
Reinforced | Max. dia 100mm and max. thickness 25mm | － | 80 | |
| Over dia. 100mm, up to 205mm, and max thickness 13mm | － | 72 | ||
| All other diameters and thickness | － | 50 | ||
| Wheels tapered on one side, Wheels tapered on both sides, Wheels, recessed on one side, Wheels, recessed on both sides, Dish wheels & Saucer wheels | 33 | 50 | ||
| One-side hubbed wheels/Duplex hubbed wheels | All other types | 33 | 50 | |
| Thread and flute grinding wheels | 63 | 63 | ||
| Relieved wheels | All other types | 33 | 50 | |
| Crankshaft and camshaft grinding wheels | 45 | 50 | ||
| Cylinder wheels and segments | 30 | 35 | ||
| Straight cup wheels and taper cup wheels | 30 | 40 | ||
| Disc wheels and segmental disc wheels | 33 | 45 | ||
| Depressed center wheels (Max. dia. 230mm and max. thickness 10mm) | Non-reinforced | － | 57 | |
| Reinforced | － | 72 | ||
| Cutting-off wheels and Depressed center cutting-off wheels | Non-reinforced | － | 63 | |
| Reinforced | － | 80 | ||
(9) The grinding wheel strength depends on the outside diameter, hole diameter, and other dimensions.
Do not use a grinding wheel in excess of its operating speed and dimensional limitations.
The dimensional limitations for types of wheels and maximum operating speed is given in Table 9-3. are required.
A grinding wheel which is used over the standard maximum operating speed is known as “special operating speed grinding wheel (high speed)”
and stricter standards are required.
Table 9-3: Dimensional limitations and maximum operating speeds (Safety requirements in Japan)
| Maximum operating speed (unit: m/s) | Types of wheels | Dimensional limitations (unit: mm) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Outside diameter (D) | Thickness (T) | Bore diameter (H) | Recessed diameter (P) | Thickness at bore (E) | Smallest diameter or internal diameter of recess (J or K) | Rim width (W) | |||
| Standard operating speeds | All types | D≤1,500 : Flat cutting-off wheels | H ≤ 0.7D | P ≥ 1.02Df + 4 | E ≥ T/4 : Straight wheels, Taper cup wheels E ≥ T/2 : Wheels, recessed on one side Wheels, recessed on both sides Dish wheels & Saucers | J・K ≥ Df + 2R | W ≤ E | ||
| Special operating speeds | 45 m/s or less | Straight wheels Wheels tapered on one side Wheels tapered on both sides Wheels, recessed on one side Wheels, recessed on both sides Hubbed wheels Duplex hubbed wheels Relieved wheels | D ≤ 1,065 | D/75 ≤ T ≤ 610 | H ≤ 0.6D | P ≥ 1.02Df + 4 | E ≥ 2/3T | J・K ≥ Df + 2R | |
| Over 45 m/s, up to 60 m/s | Straight wheels Wheels tapered on one side Wheels tapered on both sides Wheels, recessed on one side Wheels, recessed on both sides Hubbed wheels Duplex hubbed wheels Relieved wheels Depressed center wheels | D ≤ 1,065 | D/50 ≤ T ≤ 305 | H ≤ 0.5D | P ≥ 1.02Df + 4 | E ≥ 2/3T | J・K ≥ Df + 2R | ||
| Over 60 m/s, up to 80 m/s | Straight wheels Hubbed wheels Duplex hubbed wheels Depressed center wheels Flat cutting-off wheels | D≤1,500 : Flat cutting-off wheels D ≤ 760 : Other types | D/50 ≤ T ≤ 152 | H ≤ 0.33D | J・K ≥ Df + 2R | ||||
| Over 80 m/s, up to 100 m/s | Straight wheels Hubbed wheels Duplex hubbed wheels Depressed center wheels Flat cutting-off wheels | D≤1,500 : Flat cutting-off wheels D ≤ 760 : Other types | D/50 ≤ T ≤ 80 | H ≤ 0.2D | J・K ≥ Df + 2R | ||||
Remarks:
1. In this table, Df should indicate the flange diameter and R should indicate the radius of recessed grinding wheels
2. Dimensions not prescribed in this table should be optional.
Table 9-4: Additional Marking of Special-speed Grinding Wheels and Colors
| Special operating speeds | Colors |
|---|---|
| Over standard speed (see Table 9-2), up to 45m/s | Blue |
| Over 45 m/s, up to 60 m/s | Yellow |
| Over 60 m/s | Red |
Remarks:
1. The speed stripe should be approximately 20 mm in width.
2. In the case of (2), the outside diameter of the speed stripe should be larger than the flange diameter.
(10) The standard dimensions have been specified for grinding wheels.
Please request us for the grinding wheels based on the standard dimensions.
JIS specifies limit deviations.
The limit deviations are given in Table 9-6, and Table 9-7.
Notes:
(1) Limited to depressed center wheels
(2) Limited to flat cutting-off wheels
(3) Limited to mounted points and wheels and saucer wheels
(4) Limited to inserted nut cylinder
Remarks
1. Do not combine A and B.
2. For E, W, and others, use
the T standard dimension.
Table 9-5: Standard dimensions of grinding wheels
| Outside diameter (D) | Thickness (T) | Bore (H) | Recessed diameter (P) | |||
|---|---|---|---|---|---|---|
| A(ISO) | B(local) | A(ISO) | B(local) | A(ISO) | B(local) | |
| 3 4 5 6 8 10 13 16 20 25 32 40 50 63 80 100 125 150 200 250 300 350/356 400/406 450/457 500/508 600/610 750/762 900/914 1060/1067 1250 1500 | 3 4 5 6 8 10 13 16 19 22 25 28 32 38 45 50 65 75 90 100 115 125 150 180 205 230 255 280 （4） 305 355 380 405 455 510 560 585 610 660 760 915 1065 1250 1500 | 0.6 0.8 1.0 1.25 1.6 2.0 2.5 3.2 4 5 6 8 10 13 16 20 25 32 40 50 63 80 100 125 160 200 250 315 400 500 600 | 0.3 （2） 0.5 0.8 1.0 1.5 2.0 2.5 3 3.5 （2） 4 4.5 （2） 5 5.5 （2） 6 8 10 13 16 19 22 25 28 （4） 32 38 45 50 65 75 90 100 125 150 205 255 305 405 510 610 | 1.6 2.5 4 5 6 10 13 16 20 25 32 40 50.8 76.2 127 152.4 203.2 304.8 508 | 1.59 2.38 3.18 3.97 4.77 6.35 9.53 12.7 15 （1）（2） 15.88 19.05 22 （1）（3） 22.23 25.4 30 （3） 31.75 38.1 44.45 50.8 63.5 76.2 101.6 127 152.4 177.8 203.2 228.6 254 304.8 355.6 406.4 508 | 10 13 16 19 25 32 40 45 50 63 80 90 100 120 125 135 150 160 190 205 215 220 235 250 280 300 310 330 350 370 390 400 450 510 585 630 760 |
Table 9-6: Limit deviations for precision grinding
| Outside diameter | Thickness | Recessed diameter | Rim width | ||||
|---|---|---|---|---|---|---|---|
| （D） | Limit deviations | （T、U） | Limit deviations | （P） | Limit deviations | （W） | Limit deviations |
| 3 ≤ D ≤ 8 | ± 0.5 | 0.4 ≤ T、 U ≤ 1.6 | ＋ 0.2 0 | 3.2 ≤ P ≤ 8 | ＋ 0.8 0 | W ≤ 25 | ± 1.5 |
| 8 < D ≤ 20 | ± 0.8 | 1.6 < T、 U ≤ 5 | ± 0.4 | 8 < P ≤ 20 | ＋ 1.2 0 | 25 < W ≤ 50 | ＋ 2.0 － 1.5 |
| 20 < D ≤ 50 | ± 1.2 | 5 < T、 U ≤ 16 | ± 0.8 | 20 < P ≤ 50 | ＋ 2 0 | 50 < W | ＋ 3.0 － 1.5 |
| 50 < D ≤ 125 | ± 2 | 16 < T、 U ≤ 50 | ± 1.5 | 50 < P ≤ 125 | ＋ 3.2 0 | ||
| 125 < D ≤ 300 | ± 3.2 | 50 < T、 U ≤ 160 | ± 2 | 125 < P ≤ 315 | ＋ 5 0 | ||
| 300 < D ≤ 762 | ± 5 | 160 < T、 U ≤ 500 | ± 3.5 | 315 < P ≤ 900 | ＋ 8 0 | ||
| 762 < D ≤ 2000 | ± 8 | ||||||
Table 9-7: Limit deviations of grinding wheels for high-pressure grinding, cutting-off, deburring, and fettling/snagging
| High-pressure grinding | Cutting-off, deburring, and fettling / snagging | ||||||
|---|---|---|---|---|---|---|---|
| Outside diameter | Thickness | Outside diameter | Thickness | ||||
| (D) | Limit deviations | (T) | Limit deviations | (D) | Limit deviations | (T, U) | Limit deviations |
| 356 ≤ D < 508 | ± 5 | 40 ≤ T ≤ 80 | ± 1.5 | D < 250 | ± 1 | T、 U ≤ 1.6 | ± 0.2 |
| 508 ≤ D ≤ 762 | ± 5.5 | 250 ≤ D < 600 | ± 2 | 1.6 < T、 U ≤ 3.2 | ± 0.3 | ||
| 600 ≤ D < 750 | ± 3 | 3.2 < T、 U ≤ 4 | ± 0.4 | ||||
| 80 < T ≤ 152 | ± 2 | 750 ≤ D < 1000 | ± 4 | 4 < T、 U ≤ 5 | ± 0.6 | ||
| 1000 ≤ D ≤ 1800 | ± 5 | 5 < T、 U ≤ 6 | ± 0.8 | ||||
| 762 < D ≤ 914 | ± 7 | 6 < T、 U ≤ 10 | ± 1 | ||||
| 10 < T、 U ≤ 16 | ± 1.2 | ||||||
(11) Wheels should be corrected for imbalance before mounted. Out of balance wheels result in vibration marks on work surfaces.
For a grinding wheel rotating at high speed, the balance is important.
Maximum permissible unbalance (Ua) is determined using a mass ma = Ua/r, such that
ma = k1 m12/3
Where, ma is the mass whose center is located on the circumference of the grinding wheel
m1 is the mass of the grinding wheel in kilograms
r is the radius of the grinding wheel in millimeters
k1 is a coefficient which depends on the maximum operating speed and types of wheels
The values of k1 are given in the table below.
Table: Value of coefficient k1
| Maximum operating speeds m/s | Types of wheels | k1 | |
|---|---|---|---|
Standard operating speeds | Vitrified grinding wheel | 7 | |
| Resinoid grinding wheel | 6 | ||
| Resinoid deprssed center wheels with fabric reinforcement | 6.7 | ||
| Resinoid cutting-off wheel | 10 | ||
| Special operating speeds | Over 33, up to 45 | All types | 6 |
| Over 45, up to 60 | All types | 5 | |
| Over 60, up to 80 | All types | 4 | |
| Over 80, up to 100 | All types | 3 | |
Out of balance wheels which set up vibrations can result in marred work surfaces, machine damage and also cause stresses which could contribute to wheel failure.
When shutting down a wet grinding operation, the coolant should and the wheel allowed to rotate until coolant has been spun out. first be shut off and the wheel allowed to rotate until coolant has been spun out.
2. Flanges
(1) Even when the grinder and grinding wheel are manufactured in accordance with the Safety Requirements for
Machines and Grinding Wheels and JIS and well maintained, and if the wheel is not correctly mounted onto
the machine, various types of troubles, such as wheel breakage, etc. will occur.
All grinding wheels shall be mounted between flanges.
Flanges should be at least the minimum diameter specified in the Safety Requirements for Machines and
Grinding Wheels, identical in diameter and radial bearing surface to avoid cross bending pressures and
stresses in the wheel structure.Torque wrenches should be used to tighten screws at correct torque,
and care must be taken to ensure that blotters should be flat and free of burr on the contact areas.
Regularly inspect any flanges, if they are used for more than 10 years.
・Straight flange
The diameter of the straight flange must be at least 1/3 the wheel diameter, and the recess must be at least 1.5 mm.
The radial width of bearing surface must be the value given in Table 9-9(Wheel diameter and radial width of
bearing surface).
The straight flanges are given in Figure 9-4, and are used with grinding wheels for hand-held grinding and manually guided grinding.
If a reinforced flat cutting-off wheel is used at the standard speed or lower, the flange diameter must be at least 1/4 the wheel diameter.
Tensile strength of glass fiber must be 700 N/25 mm or more.
Table 9-9: Wheel diameter and radial width of bearing surface
Figure 9-4: Straight flange
| Wheel diameter (mm) | Radial width of bearing surface (mm) |
|---|---|
| 65 or less | Over 0.1Df, less than 0.26Df |
| Over 65, up to 355 | Over 0.08Df, less than 0.18Df |
| Over 355 | Over 0.06Df, less than 0.18Df |
Notes: | |
Table 9-10: Minimum dimensions for straight relieved flanges (machined)
*Safety Handbook for Grinder 12th Ed.
| D Diameter of wheel | Df Minimum outside diameter of flanges | C Radial width of bearing surface | F Minimum thickness of flange at bore | E Flange at edge of recess | Minimum wheel bore diameter | Tightening torque | |||
|---|---|---|---|---|---|---|---|---|---|
| Min. | Max. | Other types | Cut-off wheels | N・m | kg-cm | ||||
| 25 | 10 | 1.6 | 3.2 | 1.6 | 1.6 | 3.18 | － | － | |
| 50 | 19 | 3.2 | 4.8 | 3.2 | 2.5 | 6.00 | 1 | 10 | |
| 75 | 25 | 3.2 | 4.8 | 4.8 | 2.5 | 6.00 | 1 | 15 | |
| 100 | 35 | 3.2 | 4.8 | 4.8 | 3.2 | 9.53 | 9.53 | 3 | 30 |
| 125 | 42 | 4.8 | 6.4 | 6.4 | 3.2 | 9.53 | 9.53 | 4 | 40 |
| 150 | 50 | 6.4 | 13 | 10 | 4.8 | 12.70 | 9.53 | 11 | 110 |
| 180 | 65 | 6.4 | 13 | 10 | 4.8 | 12.70 | 9.53 | 17 | 170 |
| 205 | 75 | 6.4 | 13 | 10 | 4.8 | 12.70 | 9.53 | 20 | 200 |
| 255 | 90 | 8 | 16 | 10 | 6.4 | 15.88 | 12.7 | 30 | 300 |
| 305 | 100 | 8 | 16 | 13 | 8 | 19.05 | 19.05 | 34 | 350 |
| 355 | 115 | 10 | 19 | 13 | 8 | 22.23 | 22.23 | 59 | 600 |
| 405 | 140 | 13 | 25 | 13 | 8 | 25.40 | 25.4 | 108 | 1,100 |
| 455 | 150 | 13 | 25 | 16 | 10 | 25.40 | 25.4 | 118 | 1,200 |
| 510 | 180 | 16 | 32 | 16 | 10 | 38.10 | 25.4 | 255 | 2,600 |
| 560 | 190 | 16 | 32 | 16 | 11 | 38.10 | 25.4 | 275 | 2,800 |
| 610 | 205 | 19 | 32 | 16 | 11 | 38.10 | 25.4 | 319 | 3,200 |
| 660 | 220 | 19 | 32 | 16 | 13 | 50.80 | 25.4 | ||
| 710 | 255 | 22 | 38 | 19 | 13 | 50.80 | 44.45 | ||
| 760 | 255 | 22 | 38 | 19 | 16 | 50.80 | 44.45 | ||
| 915 | 305 | 25 | 50 | 22 | 19 | 50.80 | 44.45 | ||
| 1,065 | 355 | 30 | 50 | 22 | 19 | 60.32 | |||
| 1,250 | 405 | 32 | 50 | 30 | 25 | 60.32 | |||
| 1,500 | 510 | 32 | 50 | 32 | 30 | ||||
・Sleeve flange and adaptor flange
The diameters of sleeve flanges and adaptor flanges must be larger than values calculated from the formula below.
The radial width of bearing surface must be larger than values given in Table 9-12 depending on the wheel diameter and the maximum operating speeds.
A sleeve flange is given in Figure 9-5, and is used for precision grinding. An adaptor flange is given in Figure 9-6,
and is used for deburring and fettling/snagging.
Note: An adaptor must not be used at special operating speeds.
| Df ≥ k(D – H) + H | Df: Outside diameter of flanges (mm) |
| D : Diameter of wheel (mm) | |
| H : Flange pilot diameter (mm) | |
| k : Coefficient (Refer Table 9-11) |
Table 9-11: Value of coefficient k
Table 9-12: Flange types and radial width of bearing surface
| Wheel thickness (mm) | k | |
|---|---|---|
| Standard operating speeds | Special operating speeds | |
| Less than 610 | 0.13 | 0.15 |
| 610 or more, less than 760 | 0.11 | 0.13 |
| 760 or more, less than 1,065 | 0.10 | 0.12 |
| 1,065 or more | 0.08 | 0.10 |
| Grinding wheel diameter | |||
|---|---|---|---|
| Sleeve flange | Adaptor flange | ||
| Standard operating speeds | Special operating speeds | Standard operating speeds | |
| 100 or less | 4 | 5 | 8 |
| Over 100, up to 125 | 6 | 7 | 12 |
| Over 125, up to 205 | 7 | 8 | 15 |
| Over 205, up to 305 | 10 | 12 | 22 |
| Over 305, up to 405 | 13 | 16 | 22 |
| Over 405, up to 610 | 13 | 20 | 22 |
| Over 610, up to 1,065 | 16 | 25 | 32 |
| 1,065 or more | 32 | 32 | – |
Figure 9-5: Sleeve Flange
Figure 9-6: Adaptor Flange
Table 9-13: Dimensions for sleeve flanges (ISO type)
| Grinding wheel | Flange | Tightening torque | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 40kg／cm2 | 80kg／cm2 | ||||||||||||
| Bore dia. H | Dia. D | Df | C | B | N | S | V | P | Number of clamping screws x Nominal designation (Inch) | MPa | kg-cm | MPa | kg-cm |
| 76.2 | 255 | 115 | 12 | 11 | 12 | 4 | 19 | 65 | 6×M6（1/4） | 3 | 30 | 5 | 50 |
| 〃 | 305 | 115 | 12 | 11 | 12 | 4 | 19 | 65 | 6×M6（1/4） | 〃 | 〃 | 〃 | 〃 |
| 101.6 | 255 | 140 | 12 | 11 | 12 | 4 | 19 | 85 | 6×M8（5/16） | 4 | 40 | 8 | 80 | 255 | 165 | 12 | 11 | 12 | 4 | 19 | 110 | 6×M8（5/16） | 6 | 60 | 10 | 100 |
| 〃 | 305 | 165 | 12 | 11 | 12 | 4 | 19 | 110 | 6×M8（5/16） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 355 | 175 | 16 | 13 | 16 | 6 | 25 | 110 | 6×M10（3/8） | 10 | 100 | 15 | 150 |
| 〃 | 405 | 175 | 16 | 13 | 16 | 6 | 25 | 110 | 6×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 455 | 185 | 20 | 16 | 20 | 6 | 29 | 110 | 8×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 510 | 185 | 20 | 16 | 20 | 6 | 29 | 110 | 8×M10（3/8） | 10 | 100 | 15 | 150 |
| 152.4 | 355 | 200 | 16 | 13 | 16 | 6 | 25 | 130 | 6×M10（3/8） | 12 | 120 | 20 | 200 |
| 〃 | 405 | 200 | 16 | 13 | 16 | 6 | 25 | 130 | 6×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 455 | 210 | 20 | 16 | 20 | 6 | 29 | 130 | 8×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 510 | 210 | 20 | 16 | 20 | 6 | 29 | 130 | 8×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 177.8 | 405 | 230 | 20 | 16 | 20 | 6 | 29 | 160 | 8×M10（3/8） | 15 | 150 | 25 | 250 |
| 〃 | 455 | 230 | 20 | 16 | 20 | 6 | 29 | 160 | 8×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 510 | 230 | 20 | 16 | 20 | 6 | 29 | 160 | 8×M10（3/8） | 〃 | 〃 | 〃 | 〃 |
| 203.2 | 405 | 260 | 20 | 16 | 20 | 6 | 29 | 180 | 8×M12（1/2） | 20 | 200 | 30 | 300 |
| 〃 | 455 | 260 | 20 | 16 | 20 | 6 | 29 | 180 | 8×M12（1/2） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 510 | 260 | 20 | 16 | 20 | 6 | 29 | 180 | 8×M12（1/2） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 610 | 260 | 20 | 16 | 25 | 6 | 35 | 180 | 8×M12（1/2） | 〃 | 〃 | 〃 | 〃 |
| 228.6 | 405 | 290 | 20 | 16 | 25 | 6 | 35 | 205 | 8×M16（5/8） | 30 | 300 | 49 | 500 |
| 〃 | 455 | 290 | 20 | 16 | 25 | 6 | 35 | 205 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 510 | 290 | 20 | 16 | 25 | 6 | 35 | 205 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 610 | 290 | 20 | 16 | 25 | 6 | 35 | 205 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 254 | 455 | 320 | 20 | 16 | 25 | 6 | 35 | 232 | 8×M16（5/8） | 35 | 350 | 54 | 550 |
| 〃 | 510 | 320 | 20 | 16 | 25 | 6 | 35 | 232 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 610 | 320 | 20 | 16 | 25 | 6 | 35 | 232 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 304.8 | 510 | 365 | 20 | 16 | 20 | 6 | 29 | 280 | 8×M16（5/8） | 39 | 400 | 59 | 600 |
| 〃 | 610 | 365 | 20 | 16 | 25 | 6 | 35 | 280 | 8×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 760 | 380 | 25 | 19 | 25 | 6 | 35 | 280 | 8×M16（5/8） | 44 | 450 | 69 | 700 |
| 〃 | 915 | 380 | 25 | 22 | 25 | 6 | 35 | 280 | 10×M16（5/8） | 39 | 400 | 64 | 650 |
| 〃 | 1,065 | 380 ※ | 25 | 22 | 25 | 6 | 35 | 280 | 10×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 355.4 | 610 | 420 | 25 | 22 | 25 | 6 | 35 | 304 | 10×M16（5/8） | 44 | 450 | 64 | 650 |
| 〃 | 760 | 420 | 25 | 22 | 25 | 6 | 35 | 304 | 10×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 915 | 420 ※ | 25 | 22 | 25 | 6 | 35 | 304 | 10×M16（5/8） | 〃 | 〃 | 〃 | 〃 |
| 〃 | 1,065 | 440 | 25 | 22 | 25 | 6 | 35 | 304 | 10×M16（5/8） | 49 | 500 | 74 | 750 |
| 406.4 | 1,065 | 500 | 32 | 25 | 25 | 6 | 35 | 370 | 10×M20（3/4） | 88 | 900 | 127 | 1,300 |
| 〃 | 1,250 | 500 | 32 | 25 | 25 | 6 | 35 | 370 | 10×M20（3/4） | 〃 | 〃 | 〃 | 〃 |
| 508 | 1,250 | 600 | 32 | 25 | 25 | 6 | 35 | 480 | 10×M20（3/4） | 118 | 1,200 | 147 | 1,500 |
Notes:
1. * indicates that the value shall be satisfied with safety requirements.
2. V: Minimum thickness of grinding wheel mounted onto the flange (thickness at bore of recessed and relieved wheels)
Figure 9-7: Tightening screws of sleeve flange
(2) Tighten screws by using a torque wrench, and care must be taken to avoid excessive tightening.
If wheels of flanges are secured by means of a central spindle nut, the direction of the thread shall be in such relation to the direction of rotation that the nut will tend to tighten as the spindle revolves.The gradual tightening of screws on multiple screw type flanges by use of a torque wrench should be used. (Refer to Tables 9-10 and 9-13.)The tightening should proceed from one screw to one diametrically opposite and then in a crisscross manner until sufficient pressure is applied uniformly to prevent slippage. (Refer to Figure 9-7.)
(3) Do not mount a grinding wheel onto the flange incorrectly.
If the wheel is mounted onto the flange incorrectly, it will cause breakage to the wheel. Refer to Figures 9-8 and 9-9. The correct mounting method must be taken.
Figure 9-8: Straight Flange
Figure 9-9: Sleeve Flange
3. Safety guards and personal protective equipment
(1) A safety is an enclosure designed to restrain the pieces of the abrasive wheel
and furnish protection to the operator in the event that the wheel is broken during operation.The safety guard shall be the dimensions given in Table 9-14 depending on the material used. The wall thickness specified for the wheel dimensions and maximum operating speeds give in the table shall be considered as minimum values.The angle of aperture is different for the various types of grinding machines. Refer to Figure 9-10. (Article 21, Safety Requirements for Machines and Grinding Wheels)
Figure 9-10: Safety guards
| (A) Cylindrical grinding machine, centerless external cylindrical grinding machine, tool grinding machine, universal grinding machine, and similar grinding machines | (B) Portable grinder, swing frame grinding machine, high-pressure grinding machine, and similar grinding machines | (C) Surface grinding machine, cutting-off grinding machine, and similar grinding machines |
 | ||
| (D) Bench grinding machine or floor stand grinding machine for deburring, fettling, snagging, or similar work. | (F) Bench and pedestal grinding machine, or similar grinding machines other than those in (D). | |
 | ||
Table 9-14: Minimum basic thickness of peripheral and side members of cold-reduced carbon steel guards (minimum tensile strength 270 N/mm2 and minimum elongation 14%), except for band type guards
| Maximum operating speeds (m/s) | Wheel thickness (mm) | Wheel diameter(mm) | ||||||
|---|---|---|---|---|---|---|---|---|
| 150 or less | Over 150, up to 305 | Over 305, up to 405 | Over 405, up to 510 | Over 510, up to 610 | Over 610, up to 760 | Over 760, up to 1,250 | ||
| A B | A B | A B | A B | A B | A B | A B | ||
| 33 or less | 50 or less Over 50, up to 100 Over 100, up to 150 Over 150, up to 205 Over 205, up to 305 Over 305, up to 405 Over 405, up to 510 | 1.6 1.6 1.9 1.6 2.3 1.6 － － － － | 2.3 1.9 2.3 1.9 3.1 2.7 3.9 3.5 4.5 4.3 － － | 3.1 2.3 3.1 2.3 3.9 3.1 5.5 4.5 5.5 4.5 7.0 6.3 － | 3.9 3.1 4.5 3.9 6.3 3.9 6.3 4.5 6.3 4.5 7.9 6.3 8.7 7.0 | 5.5 3.9 6.3 3.9 7.0 4.5 7.0 4.5 7.0 4.5 8.0 6.3 8.7 7.0 | 6.3 4.5 7.0 4.5 7.9 5.5 7.9 5.5 7.9 5.5 9.0 6.7 9.5 8.7 | 7.9 6.3 8.7 6.3 9.5 7.9 9.5 7.9 9.5 7.9 11.0 8.7 12.7 10.0 |
| Over 33, up to 50 | 50 or less Over 50, up to 100 Over 100, up to 150 Over 150, up to 205 Over 205, up to 305 Over 305, up to 405 Over 405, up to 510 | 2.2 1.6 2.4 1.6 3.2 1.6 － － － － | 4.2 3.4 4.4 3.8 5.8 4.9 7.0 5.6 8.0 6.9 － | 4.5 3.8 5.4 4.2 6.3 5.4 8.8 7.0 9.3 7.7 10.5 9.4 － | 5.5 4.4 6.6 5.5 8.3 6.0 9.4 7.0 9.9 7.7 12.0 9.9 13.0 11.0 | 6.6 4.9 7.7 5.5 8.8 6.6 10.0 7.0 10.5 7.7 12.5 9.9 13.0 11.0 | 7.7 6.0 8.0 6.0 9.0 7.0 10.5 7.8 11.0 8.3 13.6 10.8 14.5 12.7 | 10.0 7.7 10.5 7.7 12.0 9.7 13.0 10.0 14.5 11.0 17.0 13.0 19.0 16.0 |
| Over 50, up to 80 | 50 or less Over 50, up to 100 Over 100, up to 150 Over 150, up to 205 Over 205, up to 305 Over 305, up to 405 Over 405, up to 510 | 3.1 1.6 3.1 1.6 4.7 1.6 － － － － | 7.9 6.3 9.5 7.9 11.0 9.0 12.7 9.5 14.0 11.0 － － | 7.9 6.3 9.5 7.9 11.0 9.5 14.0 11.0 15.8 12.7 15.8 14.0 － | 7.9 6.3 9.5 7.9 11.0 9.5 14.0 11.0 15.8 12.7 15.8 14.0 － | 7.9 6.3 9.5 7.9 11.0 9.5 14.0 11.0 15.8 12.7 19.0 15.8 20.0 17.4 | 7.9 6.3 9.5 7.9 11.0 9.5 14.0 11.0 15.8 12.7 19.0 15.8 20.0 17.4 | 12.7 9.5 12.7 9.5 17.9 12.0 19.0 12.7 22.0 15.8 26.9 20.0 30.0 23.8 |
Figure 9-11: Bench grinder work rest and adjustable tongue
(2) For bench, pedestal, and floor stand grinders, the work rest shall be adjusted such that the gap between the work rest and the grinding surface of the wheel shall not exceed 3 mm. Abrasive product guards (adjustable tongue) shall be designed so that for peripheral wear the width of the gap between the wheel and the abrasive product guard can be adjusted to 3 – to 10mm.
An off-hand grinder shall be equipped with a work rest which shall prevent the workpiece from
jamming between the wheel and the wheel guard. Jamming of the workpiece is a cause of wheel breakage and operator injury.
For bench, pedestal, and floor stand grinders, the work rest shall be adjusted such that the gap
between the work rest and the grinding surface of the wheel shall not exceed 3mm.
Abrasive product guards (adjustable tongue) shall be designed so that for peripheral wear the width of the gap
between the wheel and the abrasive product guard can be adjusted to 3 – to 10mm.
The work rest shall not be adjusted while the wheel is rotating.
(3) Wear eye protection and provide dust protectors during grinding operation.
During grinding operation, operators have a high risk of injuries caused by eye contact with dust, swarf or flying particles.
In order to prevent airborne particles generated by the grinding operation, it is necessary to place a safety glass sheet or a transparent plastic sheet in front of the work point. This kind of sheet is called a “shield”.
For grinding work, either install the shield on the machine or wear eye protection.
It is recommended that the eye protection be worn even when the shield is used.
If the shield is not used, the eye protection is an absolute requirement for grinding work.
Figure 9-12: Shield and eye protection
(4) Control airborne particles for grinding operation.
Fine alundum or carborundum particles which compose abrasives of grinding wheels can adversely affect health if inhaled over a long period of time. In order to prevent operators from inhaling these harmful fine particles generated during dry grinding work, wear a dust respirator or prevent dust disperse in a workplace by providing dust collectors to collect these particles at the location where they are generated.
4. Mounting and trial run
(1) Visual inspection and ring test
Prior to mounting, all wheels shall be inspected for damage and cracks caused by abusive handling or abusive storage. And gently tap the sides of the grinding wheel with a wooden mallet and use only wheels which produce a correct sound. The ring test depends on the damping characteristics of a cracked wheel to alter the sound emitted when the wheel is tapped lightly. It is subject to interpretation by the inspector and is primarily applicable to vitrified bonded wheels. To perform the ring test, wheels should be tapped gently with a light nonmetallic implement, such as the handle of a screw driver for light wheels, or a wooden mallet for heavier wheels. Tap wheels about 45° each side of the vertical center line and about 25 mm or 50 mm from the periphery. Rotate the wheel 45° and repeat the test. Do allow newly mounted wheels to run at operating speed for at least three minutes before grinding. Do not stand directly in front of a grinding wheel whenever a grinder is started.
(2) KGW’s blotters (paper or plastic) should always be used between metal flanges and wheel surfaces for uniform distribution of flange pressure.
KGW’s blotters with good quality for safety are attached to the grinding wheels.
(3) Do allow newly mounted wheels to conduct a trial run before grinding.
Allow a newly mounted wheel to run at operating speed with guard in place at least three minutes before starting to dress or grind to check for abnormalities such as machine vibration, noise and run-off of the wheel. If you find abnormalities, turn off the machine immediately and check the grinding wheel and the machine to find the cause. Once the machine is stopped, conduct the trial run at least one minute before re-starting the operation.
Flow of mounting and a trial run
