výroba rezného a brúsneho materiálu
grinding wheel factory
autorizovaný importér a distribútor

Hradná 6/188
945 01 Komárno
SLOVAKIA

tel.:
+421 35 7900020
fax:
+421 35 7900029
email:
info@swaty.sk
Safety
General rules

For a safe grinding the following agents are responsible:

  • The machine builder
  • The grinding wheel manufacturer
  • The user of grinding wheels and machines

The machine builder must guarantee for the proper stabilitiy of the grinding machine construction and for the adequate safety of the protection hoods. The grinding wheel manufacturer should ensure that the wheels are safe in grinding. This can be achieved by selection of appropriate components and adequate technological procedures. Throughout the production process inspection of the wheels is preformed whereby not only quality but especially safety in grinding is guaranteed since the safety test preformed at the end is the essential part of the control. The instructions for safe use are either on the wheel itself or on the marking labels (indication of the premissible revolutions per minute or the class of grinding).

The safety test includes:

  • Test-run at overspeed (determining wheel strength, centrifugal load),
  • Visual inspection,
  • Sound test by grinding wheels in vitrified bond with diameter bigger than 80 mm.

The test is caried out according to the DSA regulations.

The users of the grinding tools should provide for an adequate storage and transport of the grinding wheels to the grinding location. They must also provide correct mounting of the wheels. The user should never exceed the indicated maximum operating speed given on the label enclosed with each grinding wheel. The operating person must be fully familiar with rules concerning safe grinding.

When controlling the technical parameters of manufactured grinding wheels we keep to the following standards:

  • to DIN ISO 603-1 to 603-12 as standard for standard dimensions 13942
  • to DIN ISO 13942 as standard for diameter tolerances (TD), thickness tolerances (TT) and hole tolerances (TH)
  • to EN DINISO 6103 as standard for wheel balance tolerances
  • to pr EN DIN 12413, item 5, as standard for final control of the manufactured wheels.

Portable grinders belong to the most commonly used grinding machines and it is therefore surprising that working with them is often accompanied by troubles.

In addition to the general rules, the following should be considered:

  • If the machine is air driven, the speed of the spindle (revolutions per minute) should be regularly checked and (re)adjusted to correspond with the machine builder?s declaration.
  • The machine should not be operated without safety guard. This requirement does not apply to the both sides tapered wheels with mounting flanges according to DSA.
  • Side-grinding operations should never be performed with cutting-off wheels because they not withstand the excessive side pressure, so extreme caution should be paid here! Side grinding should only be performed with depressed centre grinding wheels with a thickness of at least 4 mm.
  • Operators must always be protected by protection devices such as safety goggles, safety leather aprons, gloves and other protective clothing.
Storage of the grinding tools

Abrasive tools should not be stored in rooms where they are subject to humidity (maximum allowed relative humidity is 75%). They should neither be exposed to various solvents and temperature changes, because all of these factors have a negative effect on the strength of the resinoid bonded abrasive tools. All abrasive tools should be stored as near as possible to the grinding location in order to prevent damage such as breakage etc., and to avoid the concentration of humidity and dampness during winter transports. Since abrasive tools break easily care should be taken by handling and trucks or other suitable conveyances which provide protected transporting of larger and heavier abrasive tools should be used. Suitable racks, shelves, drawers or boxes should be provided for storing various types of abrasive tools.

The following suggestion should be paid attention to:

  • Large diameter wheels are best stored in upright position on nether rack-shelves
  • Thick-wall wheels are also stored in an upright position, whereas thin-wall wheels should be laid flat on a flat surface; between wheels corrugated paper cushions should be placed as separator
  • Both thin wheels and cutting-off wheels should be laid on a flat surface to prevent twisting
  • On the upper shelves smaller grinding tools and standard shape abrasive wheels are stored
  • Abrasive sticks, mounted wheels and other small abrasive tools can be stored in boxes

Such storage rooms should be available both for new wheels and partly used wheels.

Shelf life of vitrified bonded wheels is unlimited. All resinoid bonded wheels including resinoid bonded wheels reinforced with glass reinforcements can be stored for a limited time only becauce resinoid bonds age Shelf life of non reinforced wheels is one year and of wheels with glass reinforcements 3 years. After the shelf life period expires resinoid bonded wheels must be tested for usage according to the safety standard regulations or they should be disposed of (destroyed).

Recommendation

Grinding can be:

  • Wet -with use of coolants
  • Dry -without the use of coolants

Rough grinding (snagging) and cutting-off are as a rule dry grinding operations. Coolant is used in grinding non-metals, in precision grinding, and usually also in tool grinding. Vitrified bonded grinding wheels are not affected by chemical influence of the coolants. When resinoid bonded grinding tools are used for wet grinding, special types of bond (less affected by the damaging influence of the cooling agents) should be used. In such cases customers should always indicate that the grinding tool is to be used for wet grinding. Resinoid bonds designated for wet grinding are: B03, B08, B09, B10, B11.

By wet grinding the following rules must be observed:

  • Always use plenty of coolant. The jet of the solution should have the same width as the grinding tool and it should run directly upon the workpiece at the grinding point, so that it can both wash the grinding tool and cool the workpiece simultaneously.

The coolant must meet the following requirements:

  • It must have a cooling and lubricating effect, detergent power and an anticorrosive effect
  • It should not foam
  • It should not be inflammable
  • It should not decay easily
  • It must be ecologically safe

Notice:

When wet grinding jobs are preformed, the grinding tool should be obligatory centrifuged after the grinding operation. Coolant-soaked wheels are unbalanced, which can cause wheel breakage when the machine is run again. Resinoid bonded wheels should also be centrifuged, so as to avoid the damaging effect of coolant when the wheel is not in use.

Truing and dressing of grinding tools

If during the operation the wheel gets dull or is loading, or if it looses its geometrical form, the wheel should be dressed.

When working with diamond dressers, the following should be considered:

  • When selecting a single point diamond dresser, the following chart should serve as a guideline:

    Grinding wheel diameter
    D (mm)
    Carat
    (1 karat = 0,2 g)
    100 0,25 - 0,5
    150 0,3 - 0,6
    200 0,5 - 1
    300 0,8 - 1,2
    400 1 - 1,5
    500 1,2 - 1,5
    600 2 - 3
    800 and more 3

  • The operating angle between the grinding tool and the single point of a diamond dresser should be between 10o-15o.
  • The depth of dressing should not exceede 0.03 mm.


  • The operating angle between the grinding tool and multi point diamond dresser is 90o.


  • Prior to dressing, plenty of coolant should be provided for, directed exactly upon the diamond.

A finer surface can be obtained by a smaller depth of dressing or by a smaller feed.

Mounting

The procedure:

Skilled and well trained person only should be assigned to the mounting of the grinding wheels. Prior to mounting, wheels must be suspended and given a ring test. The mounting of the wheels upon the spindle or other mounting device must be preformed without force or use of hammer and it must warrant for a safe and firm hold. The grinding wheel should be fastened by means of flanges made of cast iron, steel or similar material, except when the class of grinding or type of operation require another kind of fastening. Blotters made of compressible material (rubber, soft cardboard, felt, leather?) should always be used between flanges and wheels. After each remounting the grinding wheel should be test-run at full operating speed for at least five minutes, during which time the danger-area should be well protected. Only after the test has proven statisfactory, the wheel can be applied. The maximum premissible operating perpheral speed should never be exceeded. (The maximum operating speed is marked on the wheel or wheel label). Therefore prior to mounting, it must be ensured that the number of revolutions/min indicated on the machine does not exceed the maximum premissible rotational speed of the grinding tool. Special attention should be paid to machines with adjustable rotational speeds for grinding tools. With grinding tools that are mounted by means of screws and are therefore furnished with one or more nuts (grinding wheels, cylinders, segments), the screws should be checked for their length, because at mounting too long screws pull the nuts out.

Mounting of straight grinding wheels

Straight grinding wheels with small holes:

Mounting procedures and types of flanges for various types of grinding tools according to DSA standard regulations.

Straight grinding wheels with large holes:

D = grinding tool diameter
S = diameter of the mounting flange
Grinding wheels without safety guards

Gluing to the mounting plate

Grinding wheels and ring wheels for straight grinding, glued to mounting plates.

Screwing to the mounting plate

Grinding wheels and cylinders with inserted nuts for straight grinding, screwfastened to the plates.

Sequence of tightening screws

To tighten screws on multiple screw flanges, torque wrenches should be used. As a rule, the torque should not exceed 27 Nm. The tightening should proceed in a crisscross manner. (See figure!)

Mounting of segments

The chuck for mounting segments.

Mounting of grinding tools with central inserted components

Mounting of grinding tools with inserted nut or shank.

After the wheel mounting, the safety guard should be secured in its place!

Peripheral speeds

Maximum operating peripheral speeds

The maximum operating speed of a grinding wheel depends upon:

  • The wheel type and the dimension
  • The specification of the wheel
  • The type of grinding (forced mechanical guidance, offhand guidance)
  • The grinding machine construction

The peripheral speeds are divided into normal (standard) and higher than normal speeds (special speeds).

Table of standard maximum operating speeds (m/s) dependent upon the shape and wheel specification and class of operating.

Bond Designation Class of operating Wheel type Maximum permessible operating speed (m/s)
Vitrified V Peripheral 1, 3, 4, 5, 7, 16, 17, 18(R), 19, 20, 21, 22, 23, 24, 25, 26, 38, 39, 52 40
Side grinding 2, 6, 9, 11, 12, 31, 35, 36, 37 32
Resinoid B Peripheral 1, 3, 4, 5, 7, 16, 17, 18(R), 19, 20, 21, 22, 23, 24, 25, 26, 38, 39, 52 50
Resinoid
Fibre reinforced
BF Side grinding 2, 6, 9, 11, 12, 31, 35, 36, 37 40
Cutting 41 50

All our products are made in accordance with FEPA Safety Standards and with German VBG-UVV49 Safety Regulations.

All our products are made in accordance with FEPA Safety Standards and with German VBG-UVV49 Safety Regulations.

All peripheral speeds higher than those listed in the table of standard peripheral speeds, including the operating speed 50 m/s, are considered higher speeds. Wheels approved for special (higher) speed application are accordingly marked by means of one or two stripes in diferent colours across the wheel diameter.

Maximum operating peripheral speed (m/s) Color stripe
50 1 x blue
63 1 x yellow
80 1 x red
100 1 x green
125 1 x green 1 x blue

Application of grinding tools at higher speeds is allowed only in case if the grinding wheel is definied and declared for operations at higher speeds and this only on machines with appropriate constructions and guards. In countries with different regulations and safety requirements, usage declarations or authorizations from appropriate authorities must be obtained, such as SUVA (for Switzerland) or DSA (for Germany).

Pheripheral speeds table

Number or revolutions per minute dependent on the wheel diameter and the operating peripheral speed

D
(mm)
v (m/s)
15 16 20 25 30 32 35 40 45 50 60 63 80 100
n (rpm)
25 11500 12200 15300 19100 22900 24400 24700 30600 34400 38200 45800 48100 61100 76400
32 8950 9550 11900 14900 17900 19100 20900 23900 26900 29800 38500 37600 47700 59700

Revolutions per minute for various diameters of abrasive wheels are calculated through the peripheral speed according to the following formula:

n = 60*v*1000/D*Pi

v = peripheral speed (m/s)
D =diameter of the wheel (mm)
Pi = 3,14
n = revolutions per minute (rpm)