87

ANSI B7.1-2000

Explanatory Information(NOT PART OF ANSI STANDARD)

E 6.1 Inspection

Defective grinding wheels are unsafe andmust not be mounted. A damaged or crackedwheel might disintegrate while in operationwhich could result in personal injury.

If any evidence of cracks or other damage isfound, the wheel should be destroyed or theinformation should be reported to the manu-facturer and arrangements made for inspec-tion.

E 6.1.1 Inspection methods

Defects such as broken wheels, chips, andgouges can be detected visually.

Cracks in abrasive wheels are frequently notvisible to the naked eye. Effective test meth-ods have been developed to detect crackswhich are not detected by visual inspection.Two of these methods are the ring test andthe vibration test.

E 6.1.1.2 Ring test

If the wheel is not too heavy, it may besuspended from the hole on a small pin orfinger. (See illustration 69.) Heavier wheelsmay be allowed to rest in a vertical positionon a clean hard floor.

Illustration 69

6 Mounting

6.1 Inspection

Prior to mounting, all wheels shall be in-spected for damage and cracks.

Wheels which show any evidence of cracks,abusive handling or abusive storage shallnot be mounted.

6.1.1 Inspection methods

The user shall visually inspect each abra-sive wheel and should apply an additionalcrack detection test when a suitable test isavailable.

6.1.1.1 Visual inspection

All wheels shall be carefully inspected visu-ally to make sure that they have not beendamaged in transit, handling, storage or fromother causes.

6.1.1.2 Ring test

The ring test depends on the damping char-acteristics of a cracked wheel to alter thesound emitted when the wheel is tappedlightly. It is subject to interpretation by theinspector and is primarily applicable to vitri-fied bonded wheels. To perform the ringtest, wheels should be tapped gently with alight nonmetallic implement, such as thehandle of a screw driver for light wheels, ora wooden mallet for heavier wheels.

Tap wheels about 45° each side of the ver-tical center line and about 1" or 2" from theperiphery as indicated by the spots in fig-ures 44 and 45. Rotate the wheel 45° andrepeat the test.

88

ANSI B7.1-2000

Figure 44 Figure 45

Large, thick wheels may be given the ringtest by striking the wheel on the peripheryrather than the side of the wheel.

A sound and undamaged wheel will give aclear tone. If cracked, there will be a deadsound and not a clear ring and the wheelshall not be used.

Limitation:

Wheels must be dry and free of sawdustwhen applying the ring test, otherwise thesound may be deadened.

The ring test is not applicable to certainwheels because of their shape or size.

Examples are:

1. small wheels (4" diameter and smaller);

2. plugs and cones;

3. mounted wheels;

4. segments;

5. plate-mounted wheels;

6. inserted nut and projecting stud discwheels.

Tap the wheel gently with a nonmetallicimplement such as a wooden screw driverhandle for light wheels and a wooden malletfor heavy wheels. The best spot to tap awheel for the ring test is about 45 degreeseither side of the vertical center line andabout 1 or 2" from the periphery. (See fig-ures 44 and 45.)

If struck directly along the vertical centerline, the ring, even in a sound wheel, issometimes muffled and may give the errone-ous impression that the wheel is cracked.This is especially true with large wheels whichare supported on the floor when conductingthis test. (See figure 45.) Also, it is some-times noticeable when the wheel is sus-pended from the hole. It is recommendedthat the test be repeated after rotating thewheel 45 degrees to the right or left.

Apply this ring test immediately before mount-ing either a new or used wheel on a ma-chine. Comparison of the sound with otherwheels of the same lot and specification willallow rejection of any wheel with a suspi-ciously different ring.

89

ANSI B7.1-2000

6.1.1.3 Vibration test

The vibration test is based on the way thatloose sand or similar material is distributedon the side of a wheel when the wheel isvibrating.

To perform the vibration test, an abrasivewheel is set on a test fixture in the horizontalposition and coated with a thin layer of fine,dry sand. The wheel is vibrated gently. Asthe wheel vibrates, the sand granules re-spond to the vibration energy. If the wheel iscracked, the granules move away from thecrack; if the wheel is sound, the granules willcontinue to be uniformly distributed over theentire surface of the wheel.

The test should be conducted on both sidesof the wheel.

6.1.2 Metal centered wheels

Steel center abrasive cutting-off and dia-mond cutting-off wheels with cracks in themetal center shall not be used.

6.2 Spindle speed

It shall be determined at time of mountingthat spindle speed does not exceed the maxi-mum operating speed marked on the wheelor wheel package. Spindle speed shall bemeasured at free running speed of the ma-chine. When a partly used wheel is re-mounted, spindle speed in revolutions perminute may exceed the maximum revolu-tions per minute marked on the wheel pro-vided the maximum peripheral speed (sur-face feet per minute), established for thewheel when new, is not exceeded. (See sec-tions 1.2.72, page 8, 1.2.88, page 10, and1.2.97, page 11, for explanations and calcu-lation of peripheral speed from revolutionsper minute. Also, wheel speed conversiontable on page 10 may be helpful.)

E 6.1.1.3 Vibration test

The vibration test can be used either in lieuof or in conjunction with the ring test. Thetest is applicable to all bond types and is notimpaired by ambient noise.

Perform the vibration test before mountingeither a new or used wheel on a machine.

E 6.2 Spindle speed

Illustration 70 – Free running speed of spindlebeing measured with a tachometer

90

ANSI B7.1-2000

6.2.1 Tension speed

It shall be determined at time of mounting asteel centered diamond cutting-off wheel thatspindle speed is within +10%/-20% of thetensioned speed marked on the wheel.

6.3 Arbor hole size

Abrasive wheels shall fit freely on the spindleand maintain proper clearance under allgrinding conditions.

A controlled clearance between the wheelarbor hole and the machine spindle (or wheelsleeve or adaptor) is essential to avoid ex-cessive pressure from mounting and spindleexpansion. Therefore, wheel arbor hole sizeequal to or exceeding the dimension shownin table 22, page 92, and spindle dimen-sions shall meet requirements of section 3.3,page 32.

Tolerance for the arbor hole for steel-cen-tered diamond cutting-off wheels should be+.002/-.000" to the minimum size given intable 22, page 92.

6.4 Surface condition

All surfaces between the wheel, blotters andflanges that come in contact with each otherduring mounting shall be flat and free offoreign particles.

6.5 Reducing bushings

Reducing bushings shall be specifically de-signed, properly manufactured and fitted whenused in abrasive wheels. The bushing shall fitfreely on the spindle and maintain proper clear-ance under all conditions. Minimum machinespindle size as shown in table 1, page 34,should not be violated. Reducing bushingsshall not be used to mount a larger abrasivewheel on a grinder than those for which thegrinder was designed.

E 6.2.1 Tension speed

If the cutting-off wheel is operated at a speedsubstantially different from the speed it wastensioned for, it will not run true, i.e., it maywobble or flutter. Therefore, the user mustoperate within the recommended speedrange. Failure to do so could cause damageto or failure of the wheel's steel center, lead-ing to serious personal injury.

E 6.3 Arbor hole size

The machine spindle or adaptor size must bemaintained by the user. Worn or undersizespindles or adaptors can cause an out-of-balance condition, contributing to wheel fail-ure.

E 6.4 Surface condition

Flanges can be distorted by excessive tight-ening or burred by dropping and must beinspected each time a wheel is mounted.(See section 5.8, page 80.) Inspection forforeign particles should be made on wheels,blotters and flanges.

Presence of foreign particles in these areascan result in uneven mounting pressureagainst the sides of the wheel causingstresses that can lead to wheel failure.

E 6.5 Reducing bushings

If a reducing bushing is wider than the wheelin which it is used, it will interfere with propertightening of the flanges against the wheel.

The power required to drive a grinding wheelis transferred through the flanges. If thispower is partially or completely transferredthrough the reducing bushing, wheel failuremay result.

91

ANSI B7.1-2000

When a reducing bushing is used in thewheel arbor hole, it shall not exceed thewidth of the wheel and shall not contact theflanges. Loose reducing bushings (not me-chanically held) should not be used withwheels less than 1/8" in thickness.

Separate reducing bushings, unless suppliedor recommended by the abrasive wheelmanufacturer, shall not be used to adaptlarger hole abrasive wheels to portable, handheld tools.

6.6 Blotters

See section 5.6, page 78.

6.7 Flanges

See section 5.1, page 72.

6.7.1 Uniformity of diameter

See section 5.4, page 77.

6.8 Tightening of mounting nut andscrews

6.8.1 Single end nut

The spindle end nut shall be tightened onlyenough to drive the wheel and prevent slip-page.

Only an appropriate reducing bushing maybe used to compensate for an oversize arborhole, and substitutes, such as flat shim stock,must not be used.

E 6.8.1 Single end nut

Overtightening of the spindle end nut mayspring the flange. A sprung flange can causestress concentrations which may break thewheel. Under-tightening of the spindle endnut can permit wheel slippage which mayresult in breakage.

The means and procedure recommended bythe machine bui lding for t ightening thespindle end nut should always be followed.

Illustration 71 – The above clearly illustratesthe results encountered when the spindle end

nut is excessively tightened

92

ANSI B7.1-2000

Tab

le 2

2 –

Min

imu

m a

rbo

r h

ole

siz

es in

inch

es

WH

EE

L E

ND

US

E3/

16"

&

Und

er1/

4"3/

8"1/

2"5/

8"3/

4"7/

8"1"

1 1/

4"1

1/2"

1 3/

4"

22

3/8"

2 1/

2"3"

3 3/

8"3

1/2"

4"5"

6"8"

10"

12"

14"

16"

20"

24"

CU

TT

ING

-OF

F+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

004

+.00

6

CY

LIN

DR

ICA

L B

etw

een

Cen

ters

+.00

2+.

002

+.00

3+.

003

+.00

4+.

005

CY

LIN

DR

ICA

L C

ente

rless

+.00

2+.

003

+.00

3+.

004

CY

LIN

DR

ICA

L C

ente

rless

Reg

ulat

ing

+.00

2+.

002

+.00

2

INT

ER

NA

L+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

OF

F H

AN

D+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

002

+.00

5+.

005

SA

W G

UM

MIN

G+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1

SN

AG

GIN

G

Flo

or S

tand

(V

IT)

+.00

1+.

001

+.00

1+.

001

+.00

1

SN

AG

GIN

G

Flo

or S

tand

(O

rgan

ic)

+.00

6+.

006

+.00

6+.

007

SN

AG

GIN

G

Por

tabl

e+.

001

+.00

1+.

001

+.00

1+.

001

+.00

1

SN

AG

GIN

G

Mec

hani

cal

+.01

0+.

010

+.01

0

SN

AG

GIN

G

Sw

ing

Fra

me

+.00

4+.

004

+.00

4+.

004

+.00

6+.

006

+.00

6+.

007

SU

RF

AC

E G

RIN

DIN

G

Hor

izon

tal

+.00

1+.

001

+.00

1+.

001

+.00

1+.

002

+.00

2+.

002

+.00

2+.

003

+.00

3+.

004

TO

OL

GR

IND

ING

+.00

1+.

001

+.00

1+.

001

+.00

1+.

001

+.00

2+.

002

DIA

MO

ND

and

CB

N+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

+.00

05+.

0005

NO

MIN

AL

A

RB

OR

H

OL

E

DIA

ME

TE

R

93

ANSI B7.1-2000

6.8.2 Multiple screws

Multiple screw flanges shall be tighteneduniformly to prevent springing of the flangesand to ensure even distribution of mountingpressure over entire surface of the flanges.Flange screws shall be tightened in a criss-cross sequence similar to that illustrated infigure 46. Figure 46 illustrates only 6 and 8screw flanges but a similar sequence can bedevised for any number of screws.

Torque wrenches should be used to tightenscrews on multiple screw flanges. Appliedtorque should not exceed 20 foot poundsunless greater torque is recommend or ap-proved by the machine builder.

Screws shall be clean and free running.Screws shall be of such length as to ensureproper clamping of the wheel by the flanges.

1

2

3 4

5

6

7

81

2

43

5

6

Order of Tightening1 - 2 - 3 - 4 - 5 - 6

Order of Tightening1 - 2 - 3 - 4 - 5 - 6 - 7 - 8

Figure 46 – Sequence of tighteningscrews on multiple screw flanges

6.9 Direction and length of thread onmachine spindle

See sections 3.3.4 and 3.4.1, page 33.

6.10 Threaded hole wheels

Special consideration must be given tothreaded hole wheels of the following types:6, 11, 16, 17, 18, 18R and 19.

E 6.8.2 Multiple screws

The gradual tightening of screws on multiplescrew type flanges by use of a torque wrenchis recommended. The tightening should pro-ceed from one screw to one diametricallyopposite and then in a crisscross manneruntil sufficient pressure is applied uniformlyto prevent slippage. Care must be taken toavoid excessive tightening as it may causespringing of the flanges resulting in wheelbreakage. Excessive tightening is particu-larly dangerous if flange screws are tight-ened when the wheel mount is at operatingtemperature and then allowed to cool. Spindlecontraction during cooling may increaseflange pressure. If the resulting pressure isexcessive, it will spring the flange resultingin stresses which may break the wheel. Theuse of impact wrenches to tighten the flangescrews on sleeve adaptor flanges is not rec-ommended. This method will cause the firstscrew to have excessive torque and thenevery remaining screw likewise. It is an un-safe method to tighten multiple screws.

Maximum permissible applied torque is de-pendent on flange design and material. Sinceflange properties are determined by the ma-chine builder, his recommendations as tomaximum applied torque must be followed.Applied torque of 15 to 20 foot pounds iscommon with single wheel mounting, how-ever, some exceptionally severe operationsrequire greater torque.

Screws must be free of foreign material andthreads of screws and tapped holes must bein good condition. Otherwise, equal torqueapplied on all screws will not provide uni-form clamping force. If clean screws are notfree running, they must be replaced and/orholes retapped to provide adequate threads.

If flange screws are too long, they may bot-tom in tapped holes resulting in a looselyclamped wheel. If screws are too long, theymust be replaced with screws of correctlength.

E 6.10 Threaded hole wheels

When threaded hole wheels are used, as incups, cones and plugs, the size and mass ofthreaded hole wheels must be kept within

94

ANSI B7.1-2000

The direction of the thread shall be such thatto remove the wheel it must be turned in thesame direction it rotates when in use.

The length of the spindle shall be such thatit shall not bottom in blind threaded holetype wheels.

Spacers shall not be used between threadedhole wheels and back flanges.

Threaded hole wheel mounting should notbe used with wheels larger than 6" diameter.

Threads in threaded hole wheels should beof class 2B and should be relieved on theside fitting against the flange so as to allowthe wheel to be screwed firmly and flatagainst the back flange.

6.11 Mounting of abrasive discs (insertednut, inserted washer and projecting studtype)

Machine face plate (steel disc wheel) andmounting surface of the wheel shall be flatand free of foreign particles.

For other requirements for mounting abra-sive discs see section 3.9, page 39.

6.12 Mounting of plate mounted typewheels

Machine face plate (steel disc wheel) andmounting surface of the wheel shall be flatand free of foreign particles.

For other requirements for mounting platemounted type wheels see section 3.10,page 41.

limits which have been found safe by expe-rience for this mounting procedure.

With this type of mounting, a relieved backflange must not be used. If made with arelief, it can pull the busing out of the wheel.See illustration 72.

Illustration 72 – Mountingof threaded hole wheels

E 6.11 Mounting of abrasive discs (in-serted nut, inserted washer and project-ing stud type)

Illustration 73 – An inserted nut typeabrasive disc showing proper mounting

95

ANSI B7.1-2000

6.13 Safety guards

At the completion of wheel mounting andprior to starting the wheel, the safety guardshall be secured in place. The safety guardshall be inspected for condition and adjust-ment. All safety guard fasteners shall be inplace and properly tightened. (See section4.1, page 50, for full information and excep-tion.)

6.14 Mounted wheels

Machine speed shall be set and measured tomake certain that it does not exceed themaximum operating speed for the mountedwheel as used.

(See table 23, page 99 and tables 26through 34, pages 121-136, for explanation.)

6.14.1 Mounted wheels on portable airgrinders

The wheel mandrel shall be inserted to thefull depth of the gripping jaws of the grindercollet. (See section 10, page 117.)

E 6.13 Safety guards

Illustration 74 – A band-type guard used withType 11 cup wheel

E 6.14 Mounted wheels

Since the overhang "O" of the mandrel of amounted wheel is a factor in determining themaximum allowable operating speed, careshould be taken to assure that the overhangconforms to the limitations shown in sec-tion 10, page 117.

Illustration 75 – Dimension "O" indicatesoverhang of the mandrel

96

ANSI B7.1-2000

6.15 Types 27, 28 and 29 wheels

Types 27, 28 and 29 wheels shall be mountedwith adaptors or flanges as specified in sec-tions 5.1.2.2 and 5.1.2.3. The specially de-signed adaptors described in section 5.1.2.2shall be used to mount only Types 27, 28and 29 reinforced organic bonded wheels.

Flanges and adaptors shall be checked forflatness of bearing surface. Sprung or warpedflanges or adaptors shall not be used.

Mounts which are affixed to the wheel by itsmanufacturer shall not be reused.

At the completion of mounting, a safety guardshall be in place between the wheel and theoperator position. (See section 4.2.2.3 andfigure 13, page 53.)

6.16 Type 27A wheels

See section 5.1.2.1, page 74.

6.17 Type 2 cylinder wheels

Type 2 cylinder wheels have diameter, wheelthickness and rim thickness dimensions.Grinding is performed on the rim surface.The wheel is chucked or cemented directlyto the machine face plate which is securelyattached to the machine spindle. The ma-chine face plate shall be flat, concentric andat a 90° angle as mounted to the machinespindle. Cylinder wheels shall be used onlyon machines equipped with band type safetyguards that conform to general specifica-tions outlined in section 4.3.14, page 66.

Minimum thickness of machine face plate isthe same as that shown for disc wheels intable 2, page 39.

6.18 Segments

Segments individually chucked in suitableholding mechanisms to form a grinding unitshall be mounted in a manner prescribed bythe manufacturer of the chucking device.The safety guard should conform to thatused for cylinder wheels. (See section 6.17and specifications outlined in section 4.3.14,page 66.)

E 6.15 Types 27, 28 and 29 wheels

Types 27, 28 and 29 wheels are designed foruse on right angle head or vertical spindleportable grinders. Type 27 wheels with flatouter area are suited for notching and cut-ting operations as well as flat area grinding.Type 28 wheels with a saucer-shaped outerarea are suited for corner cleaning work andmust not be used for notching and cuttingoperations. The variance in diameter be-tween the back flange and the adaptor nutand use of side pressure in wheel operationlimit the use of this mounting to reinforcedorganic bonded wheels.

It is important when mounting Types 27, 28and 29 wheels that proper contact is madebetween the wheel and the back flange.

Flanges must be checked for flatness sincea warped or sprung flange will cause vibra-tion and possible wheel failure.

When these wheels are supplied with a throw-away type mount attached by the manufac-turer, the mount must not be reused.

E 6.17 Type 2 cylinder wheels

Illustration 76 – Examplesof Type 2 cylinder wheels

E 6.18 Segments

Some shapes are designed to be chucked atone end for the entire segment life. Thesetend to flare outward due to centrifugal forceif improperly mounted. To prevent this, it isrecommended that two retaining bands beused with these segments during operations.As the segments wear, each band should beremoved to avoid interference with the work.

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ANSI B7.1-2000

Newly mounted segments used in chuckswhich are not designed to downfeed throughthe chucking device should be securelymounted with two equally spaced retainingbands. See illustration 78.

Illustration 77 – A segmental wheel assembly

Illustration 78