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Boyer Schultz 6-12 Surface Grinder (view source)
Revision as of 17:23, 11 August 2018
, 17:23, 11 August 2018→Auth/Use Notes: wheel selection info
[[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. 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>
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>
===== Procedure for wheel inspection =====
# Suspend the wheel on a pin or a shaft that fits through the hole so that it will be easy to turn, but do not mouth the wheel on the grinder. If the wheel is too large to suspend, stand it on a clean, hard surface.
# Imagine a vertical plumb line up the center of the wheel.
# Tap the wheel about 45 degrees on each side of the vertical line, about one or two inches from the wheel’s edge. (Large wheels may tapped on the edge rather than the side of the wheel.)
# Turn the wheel 180 degrees so that the bottom of the wheel is now on top.
# Tap the wheel about 45 degrees on each side of the vertical line again.
# The wheel passes the test if it gives a clear metallic tone when tapped at all four points. If the wheel sounds dead at any of the four points, it is cracked. Do not use it.
==== Operation ====
==== Operation ====
* Magnetic chuck
* Magnetic chuck
=== Grinding wheel ===
=== Grinding wheels ===
* ID, Grit,hardness, composition
* ID, Grit,hardness, composition
** [https://www.youtube.com/watch?v=MofRhM_W-Vk Fundamentals]
** [https://www.youtube.com/watch?v=MofRhM_W-Vk Fundamentals]
| Very friable use for carbide grinding applications.
| Very friable use for carbide grinding applications.
|}
|}
=== Wheel selection ===
# First consider the material to be ground and its hardness. These effect the choice of abrasive, grift size, and grade or hardness of the wheel.
#* Aluminum oxide are best for steels, while Silicon carbide abrasives are better suited to grinding cast iron, nonferrous metals and nonmetallic materials.
#* A relatively fine grit size works best on taking heavier cuts, and can be used advantageously on soft and ductile materials that are readily penetrated.
#* The hardness of the material to be ground also affects choice of the wheel grade or hardness. A harder grade can more easily be used on soft, easily penetrated materials than on hard materials which naturally tend to dull the wheel faster. The softer grades release the dull grains more readily to present new, sharp grains to the work.
# Second factor, in selecting a wheel in the amount of stock to be removed and the finish required. These affect the choice of grit size and bond as follows:
#* A relatively coarse grit size is selected for rapid stock removal without regard for finish as rough grinding; a fine grit should be used where a high finish is desired.
#* Vitrified bonded wheels are generally used where a commercial finish satisfactory. The organic bonds, resinoid, rubber and shellac, produce the highest finish.
# The area of grinding contact between the wheel and the work affects the choice of grit size and grade.
#* A coarse grit is required when the contact area is relatively large, as in surface grinding with cup wheels, cylinders or segments, to provide adequate chip clearance between the abrasive grains. As area of contact becomes smaller and the unit pressure tending to break down the wheel face becomes greater, finer grit wheels should be used.
#* As to the grade or hardness, on large area of contact a soft grade will provide normal breakdown of the wheel, insuring continuous, free-cutting action. A harder grade, on the other hand, is needed to stand up under the increasingly higher unit pressure as the area of contact becomes smaller.
# The severity of the grinding operation affects the choice of abrasive and grade.
#* A tough abrasive like 4A Aluminum Oxide should be used for rough, heavy duty grinding of steel.
#* The milder abrasives like 32 and 38 Aluminum Oxide are best for lighter precision grinding operations on steels and semisteels, while the intermediate 57 and 19 Aluminum Oxide abrasives are used for precision and semiprecision grinding of both mild and hard steels.
#* The severity of the grinding operation also influences the choice of grade. Hard grade provide durable wheels for rough grinding such as snagging, while medium and softer grade wheels can be used for precision type operations which are less severe on the wheel.
# The speed at which the grinding wheel is to be operated often dictates the type of bond.
#* Vitrified bonded wheels should not be used at speeds over 6,500 s.f.p.m. With few exceptions, when the speed exceeds this figure, resinoid, rubber or shellac bonded wheels should be used. Note, the safe operating speed shown on the tag, wheel or blotter must never be exceeded.
# 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.
== To-Do ==
== To-Do ==