Practical Gaging
How-To Articles
Practical guidance on common measurement scenarios — from setting up a gage to interpreting results.
Ten Questions to Ask When Buying Ring Gages
While the quality of cylindrical ring gages can vary depending on the manufacturer, customers often treat these gages as commodity items. As a result, the primary question that customers ask is, "What is your price and delivery?" In reality, that should be the last question asked. Here are several questions you should pose first, to ensure that the gages you purchase truly meet your company's requirements and industry standards.
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Know Your Gage-Block Basics
Gage blocks have been used by metrologists for more than 85 years, yet they have not changed tangibly in design, application, or even accuracy in the past 70 years. Though gage blocks — defined as square, rectangular, or round shapes (manufactured of steel and other materials) that have flat and parallel opposing sides — are simple compared to most types of sophisticated gaging today, they are still the industry-standard length masters.
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Ball Measurement
Measuring and grading balls used to be a very tiring and time consuming task. The closer a group of balls are in size to each other, the better the "grade" or rank, and usually the better the final performance of where that group may be used. But to get the balls graded meant hours behind a tiny dial, with cramping fingers on tweezers, and blurry eyes after time. So we needed to find an easy, and fast way to improve this labor intense process.
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Putting Air Gages to Work
In Part I of this article, we examined the history and fundamental principles of air gaging as well as the various styles of air gaging systems in use today. This discussion will focus on the components that comprise a typical air gaging system and how they work together. We also will address the most common air gaging applications used in industrial environments.
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Electronic Bore Plug Gages
Edmunds Electronic Bore Plug Gages are manufactured with hardened steel, chrome-plated body and tungsten-carbide contacts, and designed for rigorous production use. An insulated handle contains and protects an Edmunds cartridge type electronic probe. Changing between sizes requires change of the plug only. Our electronic plugs are available in two styles and several sizes.
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Measuring Tapers
One of the most common production practices of determining a good taper from bad is a trial and error method called "blueing." Blueing is a process which uses a precision "master taper" or part having its tapered feature manufactured to more stringent tolerances on size and angle than the actual workpiece to be measured. In use, the master taper is lightly and evenly coated with a film of dycom or indelible ink, and then inserted into the mating tapered workpiece. A slight twist of the joined master and workpiece is given, then the master removed for visual inspection.
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Slot Thickness and Location Gage
A manufacturer of fluid power components needed to gage three dimensional features of multiple pump shaft slots — some as small as .078". The optimum solution would measure thickness, parallelism and straightness in one gaging operation, yet allow for more detailed examination of data on the individual features measured. For greatest economy, the system should be readily adaptable for use with a family of similar parts.
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Axial Clearance for Bearings
Every bearing in existence has some amount of clearance in the races for the balls or roller to be able to perform correctly under load. That "clearance" — commonly known as Axial Clearance for its direction in line with the axis of the shaft — needs to be measured very accurately in order to verify the bearing quality. But the vast range of sizes of different bearings makes this a formidable task.
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Radial Play
A unique arrangement between a simple PLC and the Edmunds Trendsetter automate the measurements and settings that are achieved on the Radial Play Gaging system. The task is performed by monitoring the independent motions of the outer race within a typical cycle.
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Automatic Connecting Rod Assembly Gage
A common dilemma in assembly operations is matching mating parts when there are incremental sizes from which to choose. A case in point is Harley-Davidson. The motorcycle manufacturer often had trouble matching the correct size cranks, bearings and connecting rods for its engines. The company needed to be able to sort the rods into two different sizes so that operators could assemble the correct crank bearing into each rod for proper fit.
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40 mm Artillery Shell
Most munitions measurement is usually performed in an off line fashion using quick and easy flush pin depth gages or other simple attribute functions. But when this customer talked about 625 parts per hour needing 100% inspection, Edmunds engineers listened to the charge, knowing manual gages would not fulfill the requirements.
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Checking Centrality
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Fixed Scroll Gaging Station
An air conditioning manufacturer produced its fixed sections of scroll compressors on modern CNC machine tools. The machines were performing well, but it was difficult to calculate tool wear. Worn tools continuing to cut parts made scrap. Out-of-tolerance conditions were gradual and unpredictable.
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Automatic Gaging for Gear Precision
Premier Precision, Cornelius, NC, won a contract to produce precision gear blank pinions for one of the US Big Three automakers. First it purchased six new automatic Kummer Precision boring machines to run a "lights out" part producing program scheduled 24 hours a day, seven days a week. In the process of making the gear blanks from 5120 H modified steel a 12% scrap rate emerged.
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Scanning the Horizon — Post-Process Closed-Loop Automatic Feedback Gaging
One of the notable trends in quality control for machine tool users is post-process closed-loop feedback gaging. Post-process feedback gaging is a method of effectively controlling the quality of parts by controlling the size of the parts. It is a measurement technique that enhances part quality by automatically regulating machine tool cutter positioning.
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Air Gaging vs. Contact Gaging
Contact gaging measures the dimension from surface roughness peaks of the part being measured (i.e. at plane A-A). Open nozzle air gaging measures the mean surface of the part, which is approximately the average of surface finish peaks and valleys (i.e. at plane B-B). Technically, the mean surface would be an imaginary plane established by using the material from the peaks to fill the valleys until a level or zero line is formed.
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