Changes

  Puller  - https://www.mcmaster.com/#43745a51/=1d6osq6

  Puller  - https://www.mcmaster.com/#43745a51/=1d6osq6

== Auth/Use Notes ==

== Auth/use notes ==

Danger Committee: [[User:Jim|Jim Brink]] & [[User:mct|McTavish McArdle]]

Danger Committee: [[User:Jim|Jim Brink]] & [[User:mct|McTavish McArdle]]

=== Safety ===

=== Safety ===

==== Wheel Inspection ====

==== Wheel inspection ====

[[File:Surface-grinder-wheel-inspection.jpg|thumb|right|Tap a wheel with the end of a screwdriver to test its ring]]

[[File:Surface-grinder-wheel-inspection.jpg|thumb|right|Tap a wheel with the end of a screwdriver to test its ring]]

<blockquote>When a grinding wheel is received in the shop or removed from storage, it should be inspected closely for damage or cracks. Check a small wheel by suspending it on one finger or with a piece of string. Tap it gently with a light '''nonmetallic''' instrument, such as the handle of a screwdriver.

<blockquote>When a grinding wheel is received in the shop or removed from storage, it should be inspected closely for damage or cracks. Check a small wheel by suspending it on one finger or with a piece of string. Tap it gently with a light '''nonmetallic''' instrument, such as the handle of a screwdriver. If the wheel does not give a clear ring, discard it.</blockquote>

If the wheel does not give a clear ring, discard it. All wheels do not emit the same tone; a low tone does not necessarily mean a cracked wheel. Wheels are often filled with various resins or greases to modify their cutting action, and resin or grease deadens the tone. Vitrified and silicate wheels emit a clear metallic ring. Resin, rubber, and shellac bonded wheels emit a tone that is less clear. Regardless of the bond, the sound of a cracked wheel is easy to identify.</blockquote>

<blockquote>All wheels do not emit the same tone; a low tone does not necessarily mean a cracked wheel. Wheels are often filled with various resins or greases to modify their cutting action, and resin or grease deadens the tone. Vitrified and silicate wheels emit a clear metallic ring. Resin, rubber, and shellac bonded wheels emit a tone that is less clear. Regardless of the bond, the sound of a cracked wheel is easy to identify.</blockquote>

===== Procedure for wheel inspection =====

===== Procedure for wheel inspection =====

** Balancing

** Balancing

==== Wheel Types ====

==== Wheel types ====

[[File:Surface-grinding-wheel-markings.jpg|thumb|right|Wheel type markings]]

[[File:Surface-grinding-wheel-markings.jpg|thumb|right|Wheel type markings]]

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==== Grain Size/Grit ====

==== Grain size/grit ====

<blockquote>Abrasive grains are selected according to the mesh of a sieve through which they are sorted. For example, grain number 40 indicates that the abrasive grain passes through a sieve having approximately 40 meshes to the linear inch. A grinding wheel is designated coarse, medium, or fine according to the size of the individual abrasive grains making up the wheel.

<blockquote>Abrasive grains are selected according to the mesh of a sieve through which they are sorted. For example, grain number 40 indicates that the abrasive grain passes through a sieve having approximately 40 meshes to the linear inch. A grinding wheel is designated coarse, medium, or fine according to the size of the individual abrasive grains making up the wheel. The softer and more ductile the material, the coarser the grain size. The larger the amount of stock to be removed, the coarser the grain size. The finer the finish desired, the finer the grain size.</blockquote>

 

The softer and more ductile the material, the coarser the grain size. The larger the amount of stock to be removed, the coarser the grain size. The finer the finish desired, the finer the grain size.</blockquote>

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==== Hardness Grade ====

==== Hardness grade ====

<blockquote>The grade of a grinding wheel designates the hardness of the bonded material.  A soft wheel is one on which the cutting particles break away rapidly while a hard wheel is one on which the bond successfully opposes this breaking away of the abrasive grain.

<blockquote>The grade of a grinding wheel designates the hardness of the bonded material.  A soft wheel is one on which the cutting particles break away rapidly while a hard wheel is one on which the bond successfully opposes this breaking away of the abrasive grain.</blockquote>

Most wheels are graded according to hardness by a letter system. Most manufacturers of grinding abrasive wheels use a letter code ranging from A (very soft) to Z (very hard). Vitrified and silicate bonds usually range from very soft to very hard, shellac and resinoid bonds usually range from very soft to hard, and rubber bonds are limited to the medium to hard range.

<blockquote>Most wheels are graded according to hardness by a letter system. Most manufacturers of grinding abrasive wheels use a letter code ranging from A (very soft) to Z (very hard). Vitrified and silicate bonds usually range from very soft to very hard, shellac and resinoid bonds usually range from very soft to hard, and rubber bonds are limited to the medium to hard range.</blockquote>

The grade of hardness should be selected as carefully as the grain size. A grinding abrasive wheel that is too soft will wear away too rapidly, the abrasive grain will be discarded from the wheel before its useful life is realized. On the other hand, if the wheel is too hard for the job, the abrasive particles will become dull because the bond will not release the abrasive grain, and the wheel’s efficiency will be impaired.

<blockquote>The grade of hardness should be selected as carefully as the grain size. A grinding abrasive wheel that is too soft will wear away too rapidly, the abrasive grain will be discarded from the wheel before its useful life is realized. On the other hand, if the wheel is too hard for the job, the abrasive particles will become dull because the bond will not release the abrasive grain, and the wheel’s efficiency will be impaired.</blockquote>

The harder the material, the softer the wheel. The smaller the arc of contact, the harder the grade should be. The arc of contact is the arc, measured along the periphery of the wheel, that is in contact with the work at any instance. It follows that the larger the grinding wheel, the greater the arc of contact and, therefore, a softer wheel can be used. The higher the work speed with relation to the wheel speed, the milder the grinding action and the harder the grade should be.</blockquote>

<blockquote>The harder the material, the softer the wheel. The smaller the arc of contact, the harder the grade should be. The arc of contact is the arc, measured along the periphery of the wheel, that is in contact with the work at any instance. It follows that the larger the grinding wheel, the greater the arc of contact and, therefore, a softer wheel can be used. The higher the work speed with relation to the wheel speed, the milder the grinding action and the harder the grade should be.</blockquote>

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==== Bonding Material ====

==== Bonding material ====

<blockquote>The abrasive particles in a grinding wheel are held in place by the bonding agent. The percentage of bond in the wheel determines, to a great extent, the “hardness” or “grade” of the wheel. The greater the percentage and strength of the bond, the harder the grinding wheel will be. “Hard” wheels retain the cutting grains longer, while “soft” wheels release the grains quickly. If a grinding wheel is “too hard” for the job, it will glaze because the bond prevents dulled abrasive particles from being released so new grains can be exposed for cutting. Besides controlling hardness and holding the abrasive, the bond also provides the proper safety factor at running speed. It holds the wheel together while centrifugal force is trying to tear it apart. The most common bonds used in grinding wheels are vitrified, silicate, shellac, resinoid, and rubber.</blockquote>

<blockquote>The abrasive particles in a grinding wheel are held in place by the bonding agent. The percentage of bond in the wheel determines, to a great extent, the 'hardness' or 'grade' of the wheel. The greater the percentage and strength of the bond, the harder the grinding wheel will be. “Hard” wheels retain the cutting grains longer, while “soft” wheels release the grains quickly. If a grinding wheel is 'too hard' for the job, it will glaze because the bond prevents dulled abrasive particles from being released so new grains can be exposed for cutting. Besides controlling hardness and holding the abrasive, the bond also provides the proper safety factor at running speed. It holds the wheel together while centrifugal force is trying to tear it apart. The most common bonds used in grinding wheels are vitrified, silicate, shellac, resinoid, and rubber.</blockquote>

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[[File:Surface-grinding-wheel-structure.jpg|thumb|right|Wheel structure]]

[[File:Surface-grinding-wheel-structure.jpg|thumb|right|Wheel structure]]

<blockquote>Bond strength of a grinding wheel is not wholly dependent upon the grade of hardness but depends equally on the structure of the wheel, that is, the spacing of the grain or its density. The structure or spacing is measured in number of grains per cubic inch of wheel volume.

<blockquote>Bond strength of a grinding wheel is not wholly dependent upon the grade of hardness but depends equally on the structure of the wheel, that is, the spacing of the grain or its density. The structure or spacing is measured in number of grains per cubic inch of wheel volume. The softer, tougher, and more ductile the material, the wider the grain spacing. The finer the finish desired, the closer, or more dense, the grain spacing should be.</blockquote>

 

The softer, tougher, and more ductile the material, the wider the grain spacing. The finer the finish desired, the closer, or more dense, the grain spacing should be.</blockquote>

==== Abrasive material ====

==== Abrasive material ====

# Feed rate

# Feed rate

#* The higher the feed rate, the greater the grinding pressure is. If the grinding speed of workpiece must be increased, the feed rate will be increased, then the wear of the wheel will be faster. Therefore a harder grinding wheel is required.

#* The higher the feed rate, the greater the grinding pressure is. If the grinding speed of workpiece must be increased, the feed rate will be increased, then the wear of the wheel will be faster. Therefore a harder grinding wheel is required.

== To-Do ==

== To-Do ==