Gear Geometry
While the involute curve creates the tooth shape, this is the specific circle from which that curve actually begins.
What is the Base Circle?
These are the two basic types of spur gears: one has teeth on the outside of a cylinder, and the other has teeth on the inside.
What are External and Internal spur gears?
These gears are used when shafts must intersect at exactly 90° without changing the speed of the system.
What are Miter Gears?
This type of gear drawing is the industry standard for assembly drawings because it is fast and effective.
What is a Schematic (or Simplified) drawing?
According to the "Rules for Gear Teeth," all mating gears MUST have the same value for this measurement.
What is Tooth Size (or Diametral Pitch)?
This term describes the height of the tooth that sticks out above the Pitch Circle.
What is the Addendum?
When two or more spur gears are cut onto a single, solid shaft, it is called by this name.
What is a Cluster Gear?
In a Rack and Pinion system, the round gear is the pinion; what is the official name for the flat, straight bar it moves on?
What is the Rack?
When drawing a schematic gear, the Pitch Circle must be drawn with this specific line weight.
What is a Centerline?
If a pinion has the minimum recommended 13 teeth, the gear it meshes with should have at least this many teeth.
What is 26 teeth?
This is the imaginary line or angle at which one gear tooth presses against its partner; 20° is the modern standard.
What is the Pressure Angle?
While helical gears are quieter than spur gears, they produce this unwanted lateral force on the shaft.
What is End Thrust?
These are also known as "Spiral Gears" and are used for right-angle shafts but have low load-carrying capabilities.
What are Crossed Helical Gears?
This type of drawing is used only when the exact shape of the tooth or manufacturing details are required.
What is a Detailed representation?
This visualization technique involves imagining a string unwrapping from a can to describe the path of a gear tooth.
What is the Involute Curve?
Represented by the Root Circle, this term refers to the depth of the tooth gap below the Pitch Circle.
What is the Dedendum?
Name two of the three main goals spur gears are designed to achieve.
What are Transfer Motion, Keep Speed Consistent, and Reduce Vibration/Noise?
Which specific gear in a "Worm Gear" setup is designed to "lock" the system in place when it isn't operating?
What is the Worm?
In a schematic drawing, the Pitch Circles of two meshing gears should be drawn so they are ________ to each other.
What is Tangent?
Name two of the three negative consequences that occur when an engineer breaks gear design rules.
What are Slipping, Fast Wear, and Complete Gear Failure?
If you want a system to have larger teeth for heavy-duty work, should you choose a Higher or Lower Diametral Pitch (DP) number?
What is a Lower DP number? (Lower DP = Larger teeth).
These are the two main disadvantages of spur gears when compared to helical gears.
What are Less load capacity and higher noise levels?
These gears feature offset, non-intersecting axes and are specifically noted in the slides for being "very smooth, strong, and quiet."
What are Hypoid Gears?
Name the three circles that must be present in every schematic gear drawing.
What are the Outside, Pitch, and Root circles?
Why would a machinist look at a Gear Data Table rather than just measuring the drawing itself?
What is for Precision? (The table provides the exact values for tool selection and setup).