KGW HOMECustomer SupportGrinding Wheel Use and Precautions Safe Handling and Preventing Accidents

Customer Support

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 not 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.

image

(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

(Unit: m/s)
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-side
flange 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.

image(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. image

Table 9-2:Standard maximum operating speeds for types of wheels

(Unit: m/s)
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

image



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

(Unit: mm)
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

(Unit: mm)
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

(Unit: mm)
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.

image

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
image

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:
Df indicates the flange diameter.


Table 9-10: Minimum dimensions for straight relieved flanges (machined)

*Safety Handbook for Grinder 12th Ed.


(Unit: mm)
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
(Unit: mm)
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
image

Figure 9-6: Adaptor Flange
image


Table 9-13: Dimensions for sleeve flanges (ISO type)

(Unit: mm)
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
image

(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


image

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
image

(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).
image

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
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(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

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(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

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