Are You Questioning Calibration?

Most companies have a quality department that ensures their measuring equipment is calibrated on a regular basis, but occasionally an item is questioned on whether or not it should be included in the calibration program. Calibration is also questioned when it comes to certain situations. Companies are sure to include their own equipment in the quality program to be calibrated on a regular basis, however, they often overlook employee-owned instruments which are occasionally used. If these instruments are being used to qualify product, they must also be calibrated. Companies that encourage or permit the use of employee-owned tools, must include these tools in their calibration program. The owner of these tools may not want the equipment to have a calibration sticker on it or be held accountable to a standard. This should be discussed on the front end. In fact, it may be better to prohibit the use of employee-owned tools to better track the equipment used in your process. Equipment often overlooked and called into question are hard gages. This includes gage blocks, plug gages, pin gages, ring gages, and thread plug gages. If an item is in question, think of what it’s used for. If it’s used to qualify something, it must be calibrated on a regular basis. Don’t attempt to cut costs by only calibrating tools that are used for the final inspection. Uncalibrated instruments can end up being used accidentally, and it is often hard to prove that every feature of the product is verified at final inspection. Attempting to cut costs could, instead, end up increasing costs. If final inspections reveal product is off, this could result in recalls or thousands of finished products ending up as scrap. One way to cut costs without jeopardizing the quality of your product is to analyze equipment calibration reports. Compare the results over time to see if there’s room to lengthen the calibration cycle for your equipment. If an item is costing more money in calibration compared to others, it may be time to replace the equipment. Our customers have access to their equipment calibration reports 24/7 through our online customer portal. They are able to view their previous calibrations and when calibration is due next for each piece of equipment. If you have any questions regarding calibration, equipment, or CERTLINK, don’t hesitate to reach out! SOURCES: Quality Magazine

Choose and Use the Proper Thread/Ring Gage

A highly common application for gages is inspecting threaded holes and shafts. While using plug gages to check threaded holes in manufactured parts is a popular practice, checking shaft, dowel and fastener diameter using ring gages is perhaps less common but equally important. There are also smooth ring gages for checking non-threaded parts.

Ring gages provide a go/no-go assessment of the specified dimensional tolerances or attributes of pins, shafts, or threaded studs. Ring gages are used for comparative gaging as well as for the checking, calibrating or setting of gages or other standards in a wide variety of industries, including machine tool, automotive, oil and gas exploration, and other metal working applications.

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GO THREAD RING GAGES

The go thread ring gage checks the so-called “mating size” of the external thread and screwing-on capability. In doing so, it checks the largest dimension of the external thread pitch diameter including certain form deviations in the thread, e.g. pitch and thread profile angle deviations. It also checks whether the straight flank piece is long enough, such that the curve on the external thread root does not extend too far into the profile flank. The root curve itself is not checked. The major diameter is also not checked by this gage.

The go thread ring gage must be able to be screwed on by hand along the full length of the workpiece thread without force. The go thread ring gage is subject to greater wear and should be checked at regular intervals with a wear check plug gage. It should be noted that the thread length is not less than 80% of the thread engagement length of the workpiece thread.

NO-GO THREAD RING GAGES

The no-go thread ring gage is designed to check whether the actual pitch diameter of the workpiece external thread falls below the prescribed smallest size. The external thread major and minor diameters are not tested here.

The no-go thread ring gage has a thread length of at least three threads. The thread profile has a truncated crest. The no-go thread ring gage must be monitored regularly with a wear check plug gage.

The no-go thread ring gage must not be able to be screwed onto the workpiece thread (from both sides) by hand for more than two threads without force. The two revolutions are determined by screwing off the ring gage.

SMOOTH RING GAGES FOR EXTERNAL THREAD MAJOR DIAMETERS

There are smooth go and no-go ring gages for checking thread major diameters. As the major diameter can change through thread cutting, an inspection is required after the thread has been completed. Generally speaking, a check of the external thread major diameter should be made before gaging the external thread pitch diameter.

It must be possible to push the smooth go ring gage for the external thread major diameter along the entire thread length without any force. It must not be possible to push the smooth no-go ring gage for the external thread major diameter over the workpiece thread by more than two pitches (2 x P) from the start of the thread.

SMOOTH RING GAGES FOR NON-THREADED SHAFTS

There are also smooth go and no-go ring gages used for gaging shaft diameters, especially for components that are easily deformed.

The smooth go ring gage checks the maximum shaft dimension including certain form deviations, e.g. concentricity and cylindricity. The smooth, cylindrical go ring gage must be able to be paired with the shaft over the entire length by hand without using force.

The smooth no-go ring gage checks whether the shaft has fallen below the prescribed minimum shaft dimension. It must not be possible to pair a smooth no-go ring gage with the shaft without any force.

By Michael McCue and Thomas Zeus