Theory – Hand Grinding Machines

What is the most common man made abrasive?
A Type – Aluminum Oxide.
What is the maximum rpm of a grinding wheel? Where is this found?
The maximum rpm of a grinding wheel depends on the wheel, it can be found on the blotter of the wheel.
What is the difference between truing a wheel and dressing it?
Truing a wheel is when you are making the outside concentric with the bore and restore its round shape. Dressing is when you are removing the top layer of abrasive to expose new sharp cutting material.
What are pedestal grinders typically used for?
Hand grinding (Usually tools)
What are some safety precautions for hand grinders?
-Safety glasses are a must when grinding.
-You should never exceed the wheels rpm.
-Ensure all guards are in place.
-Do not grind on the side of the wheel.
-Do not use excessive pressure.
-Do not wear loose clothing.
-When starting up the wheel stand to side as this is when it will explode if it is cracked/broken.
-Ring test before installing.
How are the shafts on a offhand grinder threaded? Why is it threaded this way?
The left wheel has a left handed thread, the right wheel has a right handed thread. This is so that the rotation of the shaft is always tightening the nut holding the wheel.
What would cause a wheel to vibrate?
A wheel will vibrate when it is not true to the bore and out of round.
A die grinder is used for hand polishing and deburring. When using them ensure you have ______ on.
A die grinder is used for hand polishing and deburring. When using them ensure you have goggles on.
What is the minimum and maximum distance in inch and metric that a tool rest can be in relation to the wheel of a pedestal grinder?
The distance between the tool rest and wheel must be at least 1/16″(1.5mm) and at the most 1/8″(3mm)
What is the function of the bond of a wheel?
The function of the bond is to hold the abrasive grains together in the shape of the wheel.
How are aluminum oxide and silicone carbide wheels identified on a wheel?
Aluminum Oxide is identified with an A and Silicone carbide with a C.
What are the 3 most common types of wheel bonds?
Vitrified(v) – Clay Based (50% of wheels)
Resinoid(b) – Plastic with resins (33%)
Rubber(r) – Strong and Flexible
What is the purpose of a grinding wheels blotter?
It is used to help distribute clamping forces and display information about the wheel such as maximum RPM, the size and RPM of the wheel etc.
What is a Ring Test? What are you looking for?
A ring test is used to test if a wheel is cracked. You must hang the wheel by its bore and tap it with something non-metallic. It should make a clear ringing sound if it is not cracked. If it is a dull sound it is cracked and should be destroyed before discarding.
What is the application of Aluminum Oxide Wheels? What about silicon carbide?
Aluminum Oxide is typically used to grind hard materials such as tools. Silicon carbide grinding wheels are used to grind low tensile strength materials, such as aluminum, brass and softer bronzes. It is also used on most non-ferrous metals.
You should always compare the rpm of the wheel to the rpm of the ____. The rpm of the ____ should never exceed the rpm of the ____.
You should always compare the rpm of the wheel to the rpm of the grinder. The rpm of the grinder should never exceed the rpm of the wheel.