Gaging Success

CMMs and other multifunctional metrology devices are becoming faster and more sophisticated, but top-quality gages and measuring tools still have an important place

As coordinate measuring machines (CMMs), vision systems, and ultra-fast probing heads gain market share, it might seem that traditional measuring tools such as bore gages and dial calipers should be approaching retirement. After all, the vernier caliper has been around since 1631, when French mathematician Pierre Vernier realized that using two overlapping scales—one fixed, the other sliding—would bring greater precision to his surveying measurements. The micrometer came along a few years later, after astronomer William Gascoigne developed a vernier screw for use in the telescope.

Granted, the measuring tools built on these concepts wouldn’t arrive until industrial pioneers Joseph Whitworth and Henry Maudslay put them to work in machine shops during the Industrial Revolution, but the fact remains that these and other handheld tools have been around for centuries. So, is it time to give them a well-earned rest?

Staying Power

“Perhaps one day someone will invent a new type of measuring device, maybe a glove with scanning capabilities or something along those lines, but, until then, there’s still plenty of need for traditional hand tools.” That’s according to Uwe Burkardt, marketing director for Hexagon Manufacturing Intelligence Division’s Tesa Technology unit, which is represented by Tesa USA, North Kingstown, R.I.

As a regular visitor to the shop floor, Burkardt is a big fan of CMMs and other advanced metrology equipment. But when it comes to staying power, he noted, top prizes should be awarded to the gages, indicators, and related tools that Tesa builds at its factory in Vaud, Switzerland. A prime example is the company’s long-running Imicor/Intrimik brand of internal micrometers.

“As with most of our devices, we’ve given the Imicor/Intrimik digital and data capabilities, but it’s essentially the same product we introduced more than 70 years ago,” Burkardt said. “This clearly illustrates that conventional measuring tools are still crucial components of the manufacturing landscape.”

Smart Simplicity

As with many things in manufacturing, however, choosing the most efficient tool for an application comes down to job quantity, part complexity, and where you’re at in the measurement process. For the CNC lathe operator who needs to quickly check a journal diameter during machine setup, there’s no substitute for the trusty micrometer. Conversely, someone making manifold blocks or turbine blades on a 5-axis machining center has little choice but to lean on a CMM for a first-article inspection.

Sitting between the two are sophisticated metrology devices such as Tesa’s Hite and Micro-Hite, 2D height gages that eliminate the need for dial indicators and Cadillac gages, not to mention the tedious manual calculations many of us learned in trade school. Development of these advanced tools—whether by Tesa or another metrology provider—points to an overwhelming need in the manufacturing community: ease of use.

“For starters, no one wants to read an owner’s manual these days,” Burkardt laughed. “That’s especially true for men. They’re more likely to just switch it on and see what it can do. That’s why I tell my team that our instruments must not only be accurate and dependable but (also) simple to use. Compounding this is the fact that skilled labor is increasingly hard to come by. Many workers today never went to trade school, or they’ve taken a second job with a manufacturing company to make ends meet and know little about it. Whatever the reason, a measurement tool must be easy enough that people can understand and use it with minimal training.”

Data Sure

Tim Cucchi, product manager for precision hand tools at L.S. Starrett Co., Athol, Mass., agreed, but pointed out another requirement for modern gaging systems: connectivity. “In July of 2020 or so, we introduced more than 100 upgraded digital micrometers, from your basic one-inch mic up to 24-inch mics [25.4-609.6], including blade mics, point mics, depth mics, and so on,” Cucchi said. “It was actually a facelift of our original electronic lines dating back to the early ’90s and included upgraded electronics, an IP67 rating for dirt and water resistance, an output port for data collection, and perhaps most importantly, wireless connectivity.”

Like Tesa and other metrology providers, Starrett is well aware of the call for fast and easy data collection. Shortly after the launch of its revamped product line came Starrett’s DataSure 4.0, a software system that interfaces with various measuring devices, radios, and hubs. According to Cucchi, this gives them the ability for short-range data transmission up to 30 feet, hundreds of yards, or even miles with its optional Yagi antenna and a remote gateway.

“Top on the list for us was a purely wireless tool—meaning micrometers, indicators, and electronic slide calipers—equipped with an embedded Bluetooth radio that provides military-grade, five-level encrypted communications,” he said. “We like to say it’s so secure that, even if we gave you the key and you opened up the safe, there’d be nothing in there for you to find. Of course, those customers who wish to avoid wireless communications altogether can simply turn off the radio.”

Cucchi doesn’t necessarily recommend this step, however. He explained that wireless connectivity eliminates the cumbersome “backpacks” and auxiliary hubs needed with older systems, greatly simplifying the implementation process. “You pick up the mic, measure a feature, and push the button. That’s it. If you’re within 30 feet [9.1 m], the data goes right to a PC, tablet, iPhone, or Android device running our software. And, like I said earlier, we can transmit much farther than that by adding a repeater or bridge.”

Nice Threads

As any machinist knows, there’s more to part measurement than calipers and micrometers. Pin and ring gages are a common sight on any shop floor, but so are ID and OD thread gages. Robert Adamiak is the gage product manager at Emuge-Franken USA in West Boylston, Mass. He noted that shops generally recognize the value of high-quality taps and thread mills, but too often they skimp when it comes to inspecting threaded parts, which is why the company decided to augment its line of cutting tools with gages of equivalent quality. Emuge-Franken, which has been producing these gages for many years in Germany, recently began stocking them in its Massachusetts headquarters for next-day delivery to U.S. customers.

“I don’t think it makes much sense to check an expensive workpiece with a cheap, imported gage,” he said. “The problem is, it’s not always easy to tell the difference between a high-quality thread gage and one that’s not.”

Adamiak ticked off a list of things to look for when gage shopping. These include “go and no-go” members made from proprietary steel hardened to 56 R (Rockwell), providing durability and long life. The go gage should have a “dirt flute” that extends the entire length to reduce wear, which he said is a special order for most manufacturers. The first thread on the go member should also be truncated for easy insertion, eliminating the “wobbling” that might otherwise occur. And the handles should be made of steel rather than the more common aluminum, with two opposing sides for gripping and two flat surfaces that make it easy to count the number of turns when checking thread depth. “Our gages have some meat to them,” he said. “You can tell right away that you’re holding a quality inspection device.”

Fine Form

Finally, Adamiak suggested that shops avoid thread gages with removable handles that increase the risk someone will inadvertently insert the wrong member when assembling the inspection tools for a job, possibly leading to scrap parts.

Eric Johnson will tell you that go and no-go thread gages—no matter how precise or well-designed—don’t tell the entire story about thread quality. Johnson, the director of marketing for The Johnson Gage Co., Bloomfield, Conn., agreed that there will always be a need for top-notch go and no-go plug and ring gages, tools he’s happy to provide, but said there are significant benefits to the “indicating version” of the ring or plug gages that his company provides.

These are robust gages available with dial or digital readouts, he explained. They’re modular in design and, unlike fixed gages, provide the operator with actual measurements and a range of functional information about the thread rather than a simple pass or fail condition. Because the systems utilize two or three-point contact and members that engage with a large cross-section of the thread, they’re able to validate its roundness, taper, and form as well as size.

“A Johnson Gage inspects the thread for size and form and takes the subjectivity out of using a fixed-limit gage,” he said. “Machine set up is often much faster, processes can be monitored, and the opportunity for scrap or rework is minimized. Yes, most people are quite comfortable with screwing a gage onto or into a part, and I’m not suggesting anyone get rid of all their traditional thread gages or micrometers. But I will say that, once someone starts using one of our inspection systems, they find it’s faster and easier to either inspect the parts for dimensional conformance or on the shop floor make predictably good threads.”

Johnson added, “When I first started with the company, most of the Johnson Gages were purchased by quality departments to demonstrate conformance to a standard or a specific customer requirement. They were more or less relegated to a lab environment. While they are still used in that manner today, the trend has been to also implement the indicating thread gages on the shop floor. This gives the operator an advantage, as they can use the resulting data to optimize setup, monitor tool life, run SPC, or chart key characteristics as specified by the customer.”

Published here: https://www.sme.org/technologies/articles/2022/august/gaging-success/