Chapter 6 Grinders and grinding wheels
A grinding wheel shall have the following functions:
1. A highest using peripheral speed for a straight grinding wheel, a dish grinding wheel, an elastic grinding wheel or a cutting- off grinding wheel shall be prescribed with models made by each of its bonder through a grinding wheel rotation-breaking test.
2. The grain of models shall be an aluminum oxide(alumina) series.
3. Sizes of the straight grinding wheel or the dish grinding wheel shall base on Attaching table 15.
4. For the grinding wheel rotation-breaking test in the subparagraph 1, it shall take over three models or samples processed in same conditions and having sizes based on Attaching table 15. The minimum rotation-breaking peripheral velocity in the tested models or samples shall be concerned as the rotation-breaking peripheral velocity of the models or samples.
5. Except the straight grinding wheel for rought grinding, the highest using peripheral velocity of a grinding wheel for mechane grinding with a normal using peripheral velocity( hereinafter referred to as the normal velocity) set in Attaching table 16 shall be below the value get from the rotation-breaking peripheral velocity in the preceding subparagraph 1 dtivided by 1.8, but the value is over the limit of the normal velocity listed in Attaching table 16, the limit is concerned.
6. Except grinding wheels in the subparagraph 5, the highest using peripheral velocity of the grinding wheel in the subparagraph 1 shall be below the value get from the rotation-breaking peripheral velocity in the subparagraph 4 divided by 2, but it is over the limit velocity set in Attaching table 16 for that using in lower normal velocity, the limit is concerned.
7. According to the type of the griding wheel and kind of bonder, the highest using peripheral velocity of the grinding wheel shall be below the value get from the highest using peripheral velocity of the straight grinding wheel set in the preceding subparagraph 2 multiplied by the value set in Attaching table 17, but it can be prescribed by the central authority for a segment type.
Each lot of the grinding wheel with the diameter over 100 millimeters shall be taken a rotation test by the velocity which is the highest using peripheral velocity of that wheel multiplied by1.5.
The grinding wheel for testing in the preceding paragraph shall be taken over 10 percent of that products. For a number below five, the five is concerned .
If all tested grinding wheels are normal, the lot is qualified. If abnormal rate below 5 percent, the others of the lot are qualified except the abnormals. However, significantly abnormal products cannot be included in the number of that test.
Grinding wheels shall implement a regular rotation- breaking test following the next paragraph. The qualified wheels can exemple the rotation test in the first paragraph. Failed grinding wheels in the regular rotation-breaking test shall be treated according to the second paragraph.
The regular rotation-breaking test is implemented by taking more than three grinding wheels having the same kind of bonder and being used in the normal velocity.If the minimum rotation-breaking peripheral velocity get from the test is over the highest using velocity multiplied by 1.8 in case of machine-grinding except coarse grinding , or over that mulitiplied by 2 in case of other grinding, those products having this kind of bonder and being used in normal velocity are qualified.
Except the elastic grinding wheel, an impact test for the dish grinding wheel shall be implemented for each kind of specifications.
The impact test in the preceding paragraph shall be taken two or more grinding wheels by impacting at two opposite points for each wheel with a 98J value as in Attaching figure 2 and Attaching table 18. For grinding wheels with a diameter not exceeding 70 millimeters, the test may be performed on grinding wheels with 70-millimeter diameter of the same type.
If the minimum value get from the impact test is beyond 0.0297J per square millimeter according to the thickness and diameter of the tested grinding wheel, products of the same specification as that under test shall be deemed compliance.
The impact test value shall be calculated in accordance with the formulas stated in Attaching table 19.
The sizes of the grinding wheel based on its highest using peripheralbe velocity and type shall have values in accordance with listed in Attaching table 20.
The grinding wheel shall use the flanges in acordance with the specifications set in the Article 90 through 94 but it is unrestricted for those using the mounting tools set in Attaching table 21.
The fixed-side flange shall be fixed on the grinding wheel with keys or screws, or by means of the shrinkage fitting, press fitting and so forth. The fastening bolts on the shaft of the grinding wheel shall be in appropriate tightness.
When the grinding wheel is mounted on the grinding machine with a safety flange usually used by a straight grinding wheel, it shall use rubber-labels.
The material of the flange shall have the equivalent tensile strength to FC150 cast irons set in the national standard CNS 2472 "gray iron castings" and withstand distortion.
The diameter and the contact width of the grinding wheel in the fixed- side and the moving- side shall be equal except the flange set in Article 94, Attaching figure 3.
The diameter of the straight flange shall be more than one third of the diameter of the grinding wheel to be mounted, a clearance be more than 1.5 millimeters and the contact width based on the diameter of the wheel be the value as shown in Attaching table 22.
If the flange sets on the cutting-off grinding wheel which has the highest using peripheral velocity below 80 meters per second and which is reinforced by means of glass-cloth material with tensile strength over 71 kilograms or other equivalents, then the diameter of the straight flange for that wheel can be over one fourth of the diameter of that wheel regardless of the provisions in the procedinging paragraph.
The diameter of a sleeve or an adaptive flange shall be calculated according to the following formula:
Df ≧ K(D-H) + H
Where: Df, D, H, and K are as follows:
Df: diameter of the fixed- flange(millimeters)
D: diameter of the grinding wheel(millimeters)
H: inner diameter of the fixed- flange(millimeters)
K: constant according to the set in Attaching table 23.
The contact width in the preceding paragraph shall be in accordance with the diameter of the grinding wheel and not less than that given in Attaching table 24.
The adapting flange shall not be set on the grinding wheel with an using velocity over than a normal velocity.
The diameter of the safety flange using on the straight grinding wheel shall be over two thirds of the grinding wheel being mounted and on the tapered two-sides grinding wheel shall be over a half of that.
The clearance of the flange in the preceding paragraph shall be over 1.5 millimeters and the contact width be over one sixth of the diameter of that flange.
The contact face between the tapered two-sides flange and the grinding wheel shall have taper over one sixteenth.
The sizes of the flange with a form as shown in Attaching figure 3 or figure 4 and used for the dish grinding wheel shall be the values in Attaching table 25 or table 25(1).
The grinding wheel shall fit a guard with the functions in Article 96 through Article 104 except an inner circular surface grinding machine.
The material of the grinding wheel guard shall use rolled steel with the following mechanical properties :
1. Tensile strength being over 28 kilograms per millimeter square and elongation over 40 percents.
2. The sum of the tensile strength(unit: kg / mm2) and the value of the twice elongation(unit: percent) being over seventy six.
The material for a portable grinder guard or a non-band guard shall be that based on the highest using peripheral velocity in Attaching table 26 regardless of restrictions in the preceding paragraph .
The material of the guard for the cutting-off grinding wheel with the highest using peripheral velocity below 80 meters per second can use aluminum with tensile strength below 18 kilograms per millimeter square and elongation over 2 percent reguardless of restrictions in the two preceding paragraphs.
Except a grinding necessary portion, the guard shall base on the following provisions to cover:
1. For the side-grinding wheel: covering the peripheral surface and the outside of fixed-side.
2. For a portable grinding wheel guard except that in the preceding subparagraph : If the peripheral plate and the fixed- side plate are made of a piece of rolled steel with seamless, then the peripheral surface of that wheel, the outside of the fixed- side and the outside of the removeing- side as shown in figure. 5 shall be covered. If the end of the peripheral plate is bent toward the removing- side by 5 millimeters as shown in Attaching figure 5 and its thickness is over that shown in Article 23(1) by 20 percentage, then the guard for the outside of the removing-side can be exempted.
3. Besides the guards in the two preceding subparagraph: The peripheral surface, the two sides including the side of the shaft end in the removing- side..
The grinding necessary portion in the preceding proviso shall base on the grinder type and provisions in the Attaching figure 6.
Except the band-type guard, the thickness of the guard that is made of rolled steel shall base on the highest using peripheral velocity of the grinding wheel, the thickness and the diameter of that wheel to be the value no less than in Attaching table 27.
Based on the type of material, the thickness of the guard that is made of cast iron, malleable iron or cast steel shall be ove the thickness get from the preceding paragraph multiplied by the coefficient in Attaching table 28 .
Except the dish grinding wheel or the cutting-off grinding wheel, the thickness of the guard that peripheral plate and fixed-side plate are made of a piece of seamless rolled steel shall base on the highest using peripheral velocity, the thickness of grinding wheel, the diameter of that wheel and the guard -plate type to be the value listed in Attaching table 29 regardless the restriction of the first paragraph in the preceding Article 98 .
The end of the removing- side plate in the preceding paragraph shall be bent as shown in the Attaching figure 7 if the construction of the peripheral plate in the fixed- side and the side plate in the removing- side is by means of a connection way.
A guard using for the dish grinding wheel with a diameter below 230 millimeters, its thickness shall base on the thickness of that wheel no less than the value in Attaching table 30 regardless of the restriction of the first paragraph in the preceding Article 98 if its peripheral plate and fixed-side plate is made of a piece of seamless rolled steel..
The top end of the guard shall be bent as shown in Attaching figure 8.
The thickness of the guard for the cutting-off grinding wheel with the highest using peripheral velocity below 80 meters per second and the guard being made of rolled steel shall base on the thickness and the diameter of that wheel and the guard- plate type to have the value listed in Attaching table 31 regardless of the restriction of the first paragraph in the preceding Article 98.
The thickness of the guard made of cast iron, malleable iron or cast steel for that wheel in the preceding paragraph, can correspond with Article 98 paragraph 2.
The thickness of the guard made of aluminum for the cutting-off grinding wheel in the first paragraph shall be no less than that the tensile strength of aluminum multiplied by the coefficient in Attaching table 32.
The thickness for the band- type guard shall base on the diameter of the grinding wheel to be a value no less than that in Attaching table 33.
The setting of that guard shall base on Attaching figure 9.
The guard shall have no holes, slots or others that will reduce its strength.
The guard for a bench grinder or a bed grinder shall have a tongue plate or other means to adjust the gap between the peripheral of grinding necessary portion and the guard to be below 10 millimeters.
The tongue plate in the preceding paragraph shall meet the following provisions:
1. It is of a plate shape.
2. The material is rolled steel set in Article 96(1).
3. The thickness is equavalent or over that of the peripheral plate of the guard , moreover it shall be over 3 millimiters and below 16 millimeters.
4. The effective cross-section area in the entire cross-section area shall be over 70 percent and the effective vertical- section area in the entire vertical-section be over 20 percent.
5. The diameter and number for mounting bolts shall base on the thickness of grinding wheel in Attaching table 34.
The grinder shall have a power blocking device that the operator can control it without leaving operating position.
The power blocking device in the preceding paragraph shall have a construction that it is easily controlled and can prevent the unexpect start of the grinder from touching, vibrating or others.
The portable grinder with power-driving , the bench grinder or the bed grinder shall meet the following provisions:
1. Screws in the electrical circuit can prevent loosing and dropping out.
2. Insulating effectiveness between the charging part and non-charging metal part has insulating performance set in national standard CNS 3265 "the electric portable grinder".
3. It has a dedicated ground terminal which shall be in compliance with that specified in CNS 3265 “the electric protable grinder.”
The bench grinder or the bed grinder shall have a workrest that can be adjusted the gap between the peripheral of grinding wheel and the workrest to be below 3 millimeters.
A portable air-type grinder shall have a governor except the nominal size is below 65 millimeters.
The grinding wheel with the diameter below 50 milimeters and its guard do not be applied to the provisions of this chapter.