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IS 13068 (1991): Bonded abrasive products - Staticbalancing of grinding wheels - Testing [PGD 9: Abrasives]

fndian Standard

BONDED ABRASIVE PRODUCTS - STATIC BALANCING OF GRINDING WHEELS -

TESTING

IS 13068: 1991 IS0 6103 : 1988

June 1991

UDC 621-922.025 : 621 - 755 : 620-l

@ BIS 1991

BPREAU OF INDIAN STANDAR.DS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR iAARG

NEW DELHI 110002

Price Group 4

IS 33068,: 1991 IS0 6103 : -198&

Indian Standard

BONDED ABRASIVE PRODUCTS - STA,TIC BALANCING OF GRINDING WHEELS -

TESTING

NATIONAL FOREWORD

This lndian Standard which is identical with IS0 6103 : 1986 ‘Bonded abrasive products - Static balancing of grinding wheels - Testing’, issued by the International Organization for Standardization ( IS0 ), was adopted by the Bureau of Indian Standards on the recommendations of the,Abrasives Sectional Committee ( PE 09 ) and approval of the Produ,ction Engineering Division Council.

The text of the IS0 standard has been approved as suitable for publication as Indian standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard.’

b) Comma ( , ) has been used as a decimal marker in the international Standard while in Indian Standards, the current practice is to use point ( . ) as the decimal marker.

The technical committee responsible for the preparation of this standard has reviewed the provision of IS0 1925 ‘Balancing - vocabulary’ and has decided that this standard is acceptable for use in conjunction with this standard.

In reporting the results of a test or analysis made in accordance with this standard, if the final value, observed or calculated is to be rounded off, it shall be done in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values@evisedJ

As in the Original Standard, this Page is Intentionally Left Blank

IS 13068 : 1991

IS0 6103 : 1986

3.2 intrinsic unbalance of a grinding wheel, r/i: The pro- duct of the mass ml of the grinding wheel and the distance e between its centre of mass G (centre of gravity) and the axis 0 of its bore (see figure 1).

I Scope and field of application

This International Standard specifies the maximum permissible values of unbalance for various types of grinding wheels in the as-delivered condition, with outside diameter equal to or greater than 125 mm and with a peripheral speed greater than or equal to 16 m/s.

It also specifies the method for measuring the unbalance and the practical method for testing whether a grinding wheel is ac- ceotable or not.

This International Standard applies to bonded abrasive grinding wheels in the as-delivered condition.

This International Standard does not apply to

- diamond, cubic boron nitride or natural stone grinding wheels;

- centreless control wheels, lapping and disc wheels, ball wheels or glass grinding wheels.

l/i =/Q-e

Figure 1

NOTES

1 The values given refer to the grinding wheel itself, independent of any unbalance which may exist in the balancing arbor or in the means of fastening it to this arbor. These various elements, together with the flanges or hub-flanges, are assumed to be balanced, homogeneous and free from geometrical defects.

2 The effects of unbalance are basically

3.3 measured unbalance, V,: The product of a massnl2, affixed to the grinding wheel to balance it, and the distance between the centre of mass G, (centre of gravity) of the mass

rn? and the axis 0 of the grinding wheel bore; in practice, this distance is equal to the radius r of the grinding wheel (see

figure 21. - additional stresses on the arbor, the machine and its mounting;

- excessive wear of the bearings;

- vibration prejudicial to the quality of machining and increased in- ternal stresses in the grinding wheel:

- increased operator fatigue.

2 Reference

IS0 1925, Balancing - Vocabulary.

3 Definitions

3.1 unbalance : The product of an offset, in millimetres, and a mass, in grams; the unbalance is therefore expressed in grams millimetres. Figure’2

3

IS 13069 : 1991 IS0 6103 : 1986

4 Permissible unbalance, U, .

On the basis of experience, the maximum permissible un- balance U, is determined using a mass M, = U,l r, such that

m,=kfi

where

ma is the mass whose centre is located on the circum- ference of the grinding wheel, in grams;

ml is the mass of the grinding wheel, in grams;

r is the radius of the grinding wheel, in millimetres;

k is a coefficient which depends on the nature and usage of the grinding wheel.

The values of k are given in the table and the values of m,, as a function of mt and k, are shown in figure 5.

The values of k have been selected on the basis of experience so that the resulting unbalance allows for normal usage of the grinding wheel.

5 Measurement of the intrinsic unbalance

Place a balancing arbor through the bore of the grinding wheel to hold its mid-plane in a vertical position. For plain wheels or wheels of similar shape, the wheel is free-standing; wheels of other shapes may be supported using suitable flanges.

Rest the balancing arbor on two parallel horizontal bevelled guide-bars or cylindrical bars (figure 31, or on a balancing stand consisting of two pairs of overlapping, freely rotating, steel discs (figure 41, so that the grinding wheel attains an equilibrium position with a minimum of friction.

The clearance between the balancing arbor and the bore of the grinding wheel shall not exceed 0,4 mm.

The.arbor and the supports (guide-bars, bars or discs) shall have an adequate surface hardness and an appropriate surface condition to minimize friction.

When the grinding wheel attains the equilibrium position, its centre of mass is then as low as possible. In this position, mark the upper peripheral point of the grinding wheel.

Rotate the grinding wheel through XI0 to bring this mark into the horizontal plane of the arbor axis.

Determine the mass m2 which, when affixed to the periphery of the grinding wheel at a position at right angles to the mark, maintains the grinding wheel in equilibrium. The amount of un- balance thus introduced, UC = mzr, is equal and opposite to the intrinsic balance of the wheel.

The value of the mass m2 is used to determine the intrinsic un- bdance of the wheel using the following formula :

Ui = U, = m2.r

6 Checking the intrinsic unbalance

A grinding wheel is only acceptable if its intrinsic unbalance Ui is less than or equal to the permissible unbalance Ua, i.e.

I/i < Ua

The testing is done with a mass

r/g ma = T-

6.1 Determination of m,

From the table, determine the coefhcient k by reading off the value according to the various parameters related to the grind- ing wheel and its application.

Figure 5 then gives the value of the mass m,, h grams) as a function of the mass ml of the wheel, in grams, and the coeffi- cient k.

6.2 Acceptance testinqpf the grinding wheel

With the grinding’ wheel mounted in accordance with the in- structions given in clause 5, place a’mass ma as determined in 6.1 on the periphery of the&ding wheel at the mark. If the wheel remains stationan/ or rotates so that the mark is at the bottom,.‘the grinding wheel is -accepted. Otherwise, it is re- jected.

4

IS 13068:1991 IS0 6103 : 1986

X

Alternative: The two bevelled guide-bars may be replaced by two cylindrical bars.

Figure 3

Figure 4

5

IS 13068 : 1991 IS0 6103 : 1986

Use

Snagging and fettling

Precision : - cylindrical grinding

- surface grinding - sharpening

Cutting

Table - Values of the coefficiel tk

. Machines

Portable

Stationary machines Swing-frame machines Other machines

Fixed high pressure

machines

Stationary machines

Other fixed machines

Portable

Stationary or oscillating

Grinding wheels

All types -

All types

Organic bond, high density, grinding wheels

D=‘<305

All types 305 <D < 610

D > 610

All types

-EL-F=&

Coefficient k

0.40 I 0.32 4 0,25

2 0.32 0.25

0.50 WO 0.32

Or63 I O,W I 0.40

1) v is the maximal peripheral speed of the wheel, in metres per second.

2) D is the nominal diameter of the wheel, in millimetres.

a05 0.07 0,l 02 0,3 0,40,5 0,7 1 2 3 4 5 678910 20 30 40 506 80100 200 300 500 1000

Mass of the wheel m,, in grams

Figure 5

Example :

For a plain wheel for precision grinding, of outside diameter D = 760 mm and mass m 1 = 68 000 g used on a stationary machine at a surface speed of 60 m/s, the coefficient k = 0,32 (see the table) and the maximum permissible mass m, = 83 g.

1

x

000

600 500

400

300

200

100

80

60 50 40

30

20

IO

0

6 5

4

3

2

103'

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Dot : No. PE 09 ( 3999)

Amendments Wued Since Publication

Amend No. Date of Issue Text Affected

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