Grinders Flashcards
What test do you preform before installing a new wheel? How is it done?
Ring test
Support the wheel by its bore and tap around it with a non metallic object. If you hear a dull noise the wheel is cracked and must be thrown out.
What rpm do you use?
The one suggested by the manufacture. Never use the a wheel with the wrong rpm.
What is the gap your tool rest should be at?
1/16
Never more then an 1/8
When grinding thin metal what must you do?
Always use the tool rest. Thin metal can jam on wheel and kick back.
What causes excessive vibration?
Unbalanced wheel
Bent or worn shaft
Bad bearings
What are the main types of hand grinders?
Bench - sharpening cutting tools
Pedastool - larger more powerful then bench
Side wheel grinder - grinding wheel is flat vs convex like a bench grinder
Angle of work rest does not change as wheel gets smaller.
Belt grinders - grinding and polishing. Useful for quickly deburring
What are grinders typically used for?
Sharpening cutting tools
Deburring
Chamfering (when precision is not crucial)
What angle do wheel guards extend past the vertical?
30-45 degrees
Where is the best location for the tool rest to be mounted?
1/16 away from wheel and just above centre.
What happens when to much pressure is applied?
Work overheats
What is a side wheel grinder best used for?
Sharpening carbide cutting tools
What is the main use of belt grinders?
Grinding and polishing operations.
Good for deburring quickly after use of a cutoff saw
What are the 4 types of wheels?
Wire wheels-used to clean work piece
Buffering wheels-used to polish work piece to high lustre
Grinding disc-cut off operations
Sanding discs-light finishing
What are the two types of abrasives for grinding wheels?
Natural abrasives-crocus, aluminum oxide, emery, Diamond.
Manufactured abrasives-silicone carbide, cubic baron nitrate, synthetic diamonds.
What are the 4 properties of abrasives?
Hardness-the ability of a material to scratch another material
Heat resistance-the ability of a material to withstand heat without becoming dull.
Toughness-the ability of a material to resist impact and pressures
Friability-the ability of material to fracture under stress.
What are the three grits?
Course
Medium
Fine
What is a bond?
Bond holds the grain together.
What are 3 common bonds?
Vitrified-(V) speeds up to 6500 rpm
Resinous-(B) speeds from 9500 rpm and 16000
Rubber-(R) speeds up to 16000
What are the 6 positions of wheel identification?
Acronym: AGGSBM ALL GOOD GRADES SHOULD BE MILLWRIGHTS
A Position 1-abrasive type G Position 2-grain size G Position 3-grade S Position 4-structure or density B Position 5-bond type M Position 6-manufacture’s record
What are the tools used to dress a wheel?
Mechanical dresser - lugs down on tool rest
Abrasive sticks
Abrasive wheels
Diamond dressers - very fine finish required
When can you grind on the side of the grinder wheel?
Only if the wheel is rated for side grinding
Nut on right hand side of grinder has which hand thread?
Nut on left hand side of grinder has which hand thread?
Right hand
Left hand
Spark plate gap should be 1/16 to ____?
1/4
What is the blotter wheel?
Paper attached to the side of the grinding wheel to protect the flanges from abrasive grits of the wheel and to display important information about the wheel. Also serve to compensate for uneven surfaces. Never mount a wheel without a blotters on both sides
Aluminium oxide abrasives are indicated on the blotter by a letter A and are used for?
Silicone carbide abrasives are indicated by a letter C on the blotter and are used for?
Grinding steel
Grinding carbide and non ferrous metals
When tightening grinding wheel why is it important not to over tighten?
Grinding wheels are brittle and break easily. Starting torque of the grinder tends to tighten the nut
When dressing a wheel why is it important to always wear a mask?
Abrasive grinding wheels create harmful dust
When a grinding wheel is glazed it means?
Abrasive particles have become dull making the wheel shiny.
A loaded grinding wheel means?
Abrasive particles become jammed with material being ground. Where takes on colour of the material being ground
What is truing a wheel?
If vibration on the wheel persist after balancing what do you do?
Remove wheel and check shaft for runout and bearing condition.
