What is the definition of "gaging inspection tool"?
A device with an established standard size that performs a physical inspection of part features. Gaging results in a pass/fail or go-no go decision.

Learn more about gaging inspection tool in the class Thread Inspection 250 below.


Inspection Training


Class Information
Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Thread Inspection 250
Description:This class provides suggestions and how-to information for inspecting threads with a range of common instruments and gages. Includes an Interactive Lab.
Prerequisites: 350110  350150 
Difficulty:Intermediate
Number of Lessons:19
Language:English, Spanish
 
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Class Outline
  • Objectives
  • The Characteristics of Threads
  • Unified Threads
  • Metric Threads
  • Thread System Requirements
  • Visual Inspection
  • Gaging Inspection Tools
  • Using the Mating Part as a Gage
  • Inspecting with the Screw Pitch Gage
  • Inspecting with the Thread Ring Gage
  • Inspecting with the Thread Plug Gage
  • Inspecting with the Thread Snap Gage
  • Variable Thread Inspection Tools
  • Inspecting with the Metal Rule
  • Inspecting with the Thread Micrometer
  • Inspecting with the Three-Wire Measure
  • Inspecting with the Indicating Thread Gage
  • Inspecting with the Optical Comparator
  • Summary
  
Class Objectives
  • Describe the criteria that influence how precisely threads are manufactured and inspected.
  • Identify the parts of a standard Unified thread specification.
  • Identify the parts of a standard metric thread specification.
  • Differentiate among the requirements of System 21, System 22, and System 23.
  • Explain the advantages of visually inspecting threads before using inspection tools.
  • Describe the characteristics of gaging inspection tools.
  • Describe the disadvantages of using a mating part as a gage.
  • Describe how to inspect threads using a screw pitch gage.
  • Describe how to inspect threads using a thread plug gage.
  • Describe how to inspect threads using a thread ring gage.
  • Describe how to inspect threads using a thread snap gage.
  • Describe the characteristics of variable inspection tools.
  • Describe how to inspect threads using a metal rule.
  • Describe how to inspect threads using a thread micrometer.
  • Describe how to inspect threads using three-wire measurement.
  • Describe the advantages of using indicating thread gages.
  • Describe how to inspect threads using an optical comparator.

Class Vocabulary

Vocabulary TermDefinition
aerospace The industry that covers machines or vehicles of flight. Aerospace manufacturers generally require fasteners made with very high precision.
allowance A specific amount of clearance or interference between threads.
anvil The fixed jaw on a micrometer or a set of calipers.
clearance An amount of space or distance between two objects.
cone and vee rolls Parts of an indicating thread gage that measure pitch diameter. The vee measures the crest flanks, and the cone measures the opposite root flanks.
dental plaster A white powder used by dentists to make casts of patients' teeth.
drunken thread A condition in which the crest of a thread or threads wavers or is uneven.
full form segments A pair of rectangular blocks on an indicating thread gage that each have a concave, threaded side. Full form segments are used to measure functional diameter.
functional diameter The smallest or largest pitch diameter that fits onto a screw or into a nut, including all of the form deviations such as lead, thread angle, taper, and roundness. Functional diameter is a measure of the ability to assemble the thread.
gaging inspection tool A device with an established standard size that performs a physical inspection of part features. Gaging results in a pass/fail or go-no go decision.
go gage A gage on or in which a good part should fit easily.
go-no go gage A device with an established standard size that performs a physical inspection of part features to determine whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
go-no go gaging The use of a gage to determine whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
indicating thread gage A variable thread gage that has a dial or digital readout that tells where a measurement falls within the tolerance range.
inspection gage A gage used by an inspector to pass or reject finished parts.
interference An amount of overlap between two objects.
ISO metric thread A standard thread form based on millimeters that was developed for use in Europe.
lead The distance that a screw travels in one revolution.
major diameter The diameter from crest to crest of an external thread or the diameter from root to root of an internal thread.
mating part The object that a workpiece has been manufactured to fit. Nuts and bolts are mating parts of each other.
maximum material limit The most amount of material that an object may have and still pass inspection.
metal rule A very precise metal ruler with an inch scale on one side and a metric scale on the other. Metal rules can be used to inspect OD threads.
metric designation The letter "M" that begins all metric thread designations.
minimum material limit The smallest amount of material that an object may have and still pass inspection.
minor diameter The diameter from root to root of an external thread or the diameter from crest to crest of an internal thread.
multi-rib roll Cylinders on an indicating thread gage that measure functional diameter size. The rolls make full contact with the part's threads except for a small amount of clearance at the crests and roots.
no go gage A gage on or in which a good part should not fit.
nominal diameter The overall diameter of the part. Nominal diameter is one of the parts of a metric thread specification.
nominal size The size by which something is known, which may be different from its actual, measurable size. A wooden 2 x 4 is actually 1 3/4 x 3 3/4 inches.
optical comparator A sophisticated measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features.
pitch The distance from one thread groove to the next, measured from crest to crest.
pitch count The number of threads in an inch or, in the case of a metric thread, the decimal equivalent of the number of threads in a millimeter.
pitch diameter The measured distance between the pitch points taken in the groove between the threads. Pitch diameter is one of the most important dimensions in thread inspection.
plaster-of-Paris A white powder that is mixed with water, poured into a vessel or formed into a shape, and allowed to harden.
reference gage A gage used to confirm the accuracy of working and inspection gages.
roll thread snap gage A snap gage with free-turning, threaded rolls that wrap around the workpiece threads.
screw pitch gage A fan-like device comparable to a set of keys, each of which has an edge of symmetrical points calibrated to a particular thread pitch.
setting plug Part of a thread ring gage that is used to adjust the ring's diameter. After calibration, the plug is often sealed with wax.
System 21 A thread tolerance specification stating that threads must have interchangeable assembly and pass a go-no go inspection. System 21 appears in Federal Standard H28/20.
System 22 A thread tolerance specification stating that threads must have interchangeable assembly and size control at minimum and maximum material limits. System 22 appears in Federal Standard H28/20.
System 23 A safety critical thread tolerance specification stating that threads must conform with specifications for pitch diameter, functional diameter, major diameter, minor diameter, and surface finish. System 23 appears in Federal Standard H28/20.
thread A raised, helical rib or ridge around the interior or exterior of a cylindrically shaped object. Threads are found on screws, nuts, and bolts.
thread gage A gage that uses its threads to measure the accuracy of other screw threads. A thread gage is either a working gage, an inspection gage, or a reference gage.
thread micrometer A U-shaped measuring instrument with a V-shaped anvil and a cone-shaped spindle used to measure threads.
thread plug gage A cylinder of heavy metal with threaded ends used to check ID threads. A plug gage is also used to calibrate thread ring gages.
thread ring gage A disk of heavy metal with a central, threaded hole made to match a particular OD thread. The gage is screwed onto the part being inspected as though the two are mating parts.
thread series A thread designation that identifies the coarseness or fineness of threads.
thread snap gage A C-shaped device designed with either an upper and lower roll wiggled into place or one stationary roll and two go and no-go rolls, respectively. Thread snap gages with dial indicators are variable inspection devices.
threads per inch The decimal equivalent of the number of threads in an inch.
threads per millimeter The decimal equivalent of the number of threads in a millimeter.
three-wire measurement A thread inspection method that uses three wires of equal diameter placed at three different points on a thread. The inspector places a micrometer in simultaneous contact with the wires and takes measurements.
tolerance class A number and letter combination that indicates the degree of fit and whether it is an internal or external thread.
Unified thread A standard thread form based on inches that was developed by the U.S., Canada, and Great Britain.
working gage A gage used on the shop floor, often by the machine operator, to inspect parts.