Measuring internal and external thread

Posted on 30 Apr 2019 and read 853 times
Measuring internal and external threadAtlas Copco — a leading engineering group manufacturing industrial tools and equipment — is now measuring internal threads on its hydraulic bolt-tightening tools with the help of a Gagemaker Mic Trac gauge-setting system from Bowers Group (

Atlas Copco was founded in 1873, and its manufacturing facility in Wolverhampton is a new ‘state of the art’ “global bolting innovation centre” and the headquarters of Tentec Ltd, a leading provider of bolt-tightening solutions.

Part of the Atlas Copco group, Tentec designs, manufactures and distributes a wide range of hydraulic bolt-tightening tools used in both land-based and sub-sea applications.

Atlas Copco identified the need to further develop the way it checked internal threads on components; instead of using ‘go/no-go’ gauges, the company required a measurement method that was more specific for certain applications.

Bowers provided Atlas Copco with the Gagemaker system to measure the internal threads on a variety of components and provide customers with detailed feedback on tolerance.

For example, instead of giving a ‘pass’ or ‘fail’ result, Atlas Copco can now specify the ‘exact measurement’ with which the tolerance has been met — or missed.

Quality inspection manager Darren Cleaver said: “Most of the machinists here at Atlas Copco in Wolverhampton now use the Gagemaker system, and its flexible measurement capabilities have enabled us to halve the number of gauges we buy.

"We currently use it primarily for measuring threads, but we plan to have several units in place throughout the business for other manufactured parts.

Our next aim is to use a Gagemaker to measure internal and external splines, thereby giving us increased accuracy and a higher level of control over the manufacturing process.

“Many of the components manufactured by Atlas Copco are nickel plated in order to provide corrosion resistance for parts that will typically be used in sub-sea applications and exposed to salt water.

"Components used in the oil and gas industry are also subjected to extremely high pressures.

For example, if an error in machining or measurement results in an oversize thread where high pressure is a factor, it could result in what is commonly known as ‘thread-strip’, so it is imperative that stringent manufacturing and inspection processes are adhered to.”

Process development

Members of the quality team at Atlas Copco previously used ‘go/no-go’ gauges as measurement inspection tools; and while these gauges are an integral part of the quality process used in manufacturing components at Atlas Copco — and are perfectly adequate — a more advanced method of measurement was required in order to further develop the measurement process for critical applications.

Now, if one of Atlas Copco’s old gauges is out of calibration, the team no longer need to replace it, as the Gagemaker can now be used, saving Atlas Copco a significant amount of money.

Accuracy has also increased due to the ability to measure components at various stages of the manufacturing process.

The old gauges only allowed operators to measure components at the end of the process, which meant that if a mistake had been made, it would often be too late to correct, resulting in the parts being scrapped.

The Gagemaker system allows dimensions to be checked at intervals throughout the manufacturing process, enabling machine adjustments to be made mid-way through manufacture to achieve the required accuracy.

The connectivity that the Gagemaker system offers is also of benefit to Atlas Copco, as it provides a serial peripheral interface that transfers data to spreadsheets “at the touch of a button” and allows Atlas Copco to show customers that the manufactured components meet ISO standards and British standards.

The Gagemaker Mic Trac Gauge Setting System used by Atlas Copco has an internal range up to 24in and an external range from 0.5 to 25.5in.

This multi-use gauge-setting system sets or zeros most gauges with the use of interchangeable anvils or blocks; it also incorporates the ForceLok feature, which provides a constant anvil force that improves repeatability from operator to operator.

This ‘electronic, adjustable calibration and measurement centre’ can inspect parts, pre-set indicator system gauges, and calibrate a variety of hand-held inspection gauges.

The Mic Trac system has receiver pads that are precision-ground in matching sets and are used as parallel surfaces for measuring or holding fixtures. Moreover, the system can be used on the shopfloor or in a calibration lab.

Mr Cleaver concluded: “The Gagemaker has certainly helped us on our way to complete digitalisation, which is one of our aims for the future.

“The connectivity and data transfer capabilities it provides have really helped to streamline our processes.”

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