By Kennedy Smith

One of the most common and widely used benchtop tools is the height gage. You may think that their name says it all: Height gages measure height, of course. But after a century of improvement, height gages have emerged as highly versatile tools, able to measure a great deal more than their name might suggest. If you’re looking for something more capable than calipers but not quite as complex as a coordinate measuring machine, a height gage could be the perfect solution.

Height gages have been in existence since the turn of the 20th century, says Scott Robinson, from the technology services department at The L.S. Starrett Co. Vernier-type calipers were standard tools at that point. "It didn’t take long before people said, ‘If we’ve got a device to measure horizontally, maybe we ought to put a base on it and stand it vertically to measure height,’" Robinson explains.

The subsequent evolution of the height gage has remained steady. In the years that followed their inception, Vernier height gages became common tools. The trouble with Vernier height gages, however, is that they rely on users’ skill. For many years, a typical accessory for a Vernier height gage was a magnifying glass to assist the user in determining which lines truly matched up.

During the 1970s, dial calipers began to emerge as "easier to read" tools. Dial height gages quickly followed. The dial height gage features a round-faced dial with an arrow pointed toward graduations that indicate height. "It was much faster and as accurate as the Vernier height gage," notes Robinson.

The mid-1980s were a time of technological growth, during which the first electronic height gages emerged. Instead of manually operating the gage and reading a dial indicator, electronic reading tools, like touch-trigger probes, can capture the exact measurement of a material and translate it onto an LCD screen.

Although more advanced versions of height gages are repeatedly being introduced to market, there’s still enough of a need for the old-fashioned, straightforward Vernier and dial height gages that they remain popular items in gage manufacturers’ catalogs.

Types of height gages

All height gages, whether manufactured in 1902 or 2002, carry basically the same features. They all have a vertical column, anywhere from 6 to 36 inches long (custom-made height gages can extend even higher), attached to which is a unit that slides up and down. An arm protrudes from the gage, coming into direct contact with the material being measured. Each height gage features a solid base, giving the vertical column enough stability that it remains at a right angle to the table’s surface. What separates one height gage from another depends on the technology you add to these basic features. Here are some different types of height gages available:

• Vernier height gage. A height gage with graduated scales featuring marks of measurement both on the vertical column and on the arm. The graduations line up to indicate the most accurate height. Adjustments are made manually using a knob for precise positioning.

• Dial height gage. An analog-reading height gage featuring a round dial attached to the slide. The dial reads graduations of measurement, and the user adjusts position manually.

• Digital dial height gage. Like a dial height gage, but with a counter for more precise measurement. For example, the counter will read to tenths of an inch, and the dial will read to one-thousandths of an inch.

• Electronic digital height gage. A height gage featuring a digital display of measurements. These units can also include features such as instant inch-to-millimeter conversion, a hold option that temporarily saves your measurements and the ability to set any position to zero.

In addition to the several types of height gages available, there’s a wide variety of height gage accessories. These include:

• Riser blocks. Precisely measured blocks that increase the range of a height gage

• Scribers. Instruments attached to the arm of the height gage that mark the material for later machining

• Probes. Parts attached to the arm that come into direct contact with the part being measured. Measurement is triggered when the probe touches the part. Probes of various shapes and sizes measure grooves, diameters, bore centerlines and such.

• Granite surface plate. A primary reference surface. Measurement with a height gage is typically performed atop a granite surface plate. When purchasing a height gage, it’s important to consider this additional cost.

• Height gage software. If the height gage is capable of direct output, consider purchasing accompanying software to help track measurements.

According to industry experts, there’s no such thing as a good height gage or a bad height gage. In fact, the only way you could end up with a "bad" height gage is if you choose the wrong one for your particular need. Height gages can be used for the simplest of measurements, from basic go/no-go applications to advanced mapping of complex parts.

Height gage applications

"Applications for height gages are numerous, from simple step and height measurements to sophisticated 2-D applications like diameters and bolt-hole patterns," notes Dennis Traynor, vice president of sales and product support services for Mitutoyo America Corp. "They’re ideal for parts that have single or 2-D tolerancing and accuracy requirements."

A basic use for a height gage would be taking sample measurements of manufactured parts to make sure they’re within tolerances. For example, a maker of beverage containers must make sure its cans are exactly 5 inches tall. If they’re too tall or too short, they could jam in the chute of a vending machine.

A step up from this simple use of a height gage would be scribing material for later machining. For example, a machinist needs to cut a 1-inch groove exactly 4 inches from the base of a piece of steel. The machinist would take that piece of steel to the height gage, measure exactly 4 inches from the base, lock the mechanism in place and scratch a 1-inch groove into the steel using a scriber. The material would then be marked for later work.

An even more sophisticated use for a height gage is mapping the parameters of a piece of equipment. For example, an engine block manufacturer needs to know that its part is accurate according to its blueprint. Once the engine block is in position on the granite surface plate, an engineer would use a height gage to determine the location, high points and low points of bores, shafts, bearings and other part features. This is often accomplished by performing two-axis measurement with the height gage.

In order for a height gage to perform two-axis measurement, the operator must measure a part in one axis and then rotate the part 90 degrees and perform a second set of measurements in the same sequence. Software programs have emerged that enable an operator to input a part’s dimensions; the software then calculates those dimensions and displays them in 2-D.

Buyer questions and costs

With so many different types of height gages and even more applications for them, a potential height gage buyer may feel overwhelmed, not knowing where to start. Most experts agree, however, that the most important consideration is to determine exactly what you’ll be using your new tool for. "There’s a number of things buyers need to establish," says George Schuetz, director of precision gages at Mahr Federal Inc. "How big is the part? How skilled are the operators? Where in their facility will the height gage be housed? How many different parts do they want to measure? Once they’ve defined their criteria for taking measurements and determined their budget, buyers can then seek a height gage that matches those criteria."

Some common questions to keep in mind when purchasing a height gage are:

• What accuracy can I expect?

• What is the repeatability of the readings?

• How easy is this to use? How much instruction will the operators need?

• Can the batteries be recharged, or do I have to replace them? How often?

• How far away do I have to send the height gage for repairs?

• How will the shop floor environment affect the height gage’s readings?

• How adaptable is the height gage to upgrades?

• What customer support does the company offer?



Fred V. Fowler III, vice president of sales and marketing at Fred V. Fowler Co., urges buyers to keep the operator in mind when purchasing a new piece of equipment. "When you have a height gage with more functions than you need, people are going to gravitate away from it," he says. "You’re going to be stuck with a $6,000 instrument that nobody uses because everyone’s afraid to turn it on." Instead, Fowler suggests the height gage should contain four or five basic functions. "You can get 90 percent of what you need done with just the basic features of a height gage," he says. "If you need more, then that’s when you can start purchasing add-ons."

Schuetz stresses that the best height gages will have as little operator influence as possible. "They should have the capability of being motorized so that they always test the part with the same force," he says. "Part programming for repetitive operations is a must."

There are so many different types and sizes of height gages that prices vary greatly. The simplest Vernier height gage starts at about $50, but highly sophisticated models can cost more than $10,000.

Custom-made height gages can carry even heftier price tags. Don’t forget that purchasing a height gage may also mean purchasing a granite surface plate, extra batteries, gage blocks, special probes and software.

During an economic crunch, a height gage can serve as a suitable alternative to a CMM. "As long as you have time, modern height gages can measure just about any part feature," notes Traynor. However, if you’re trying to measure a part with full 3-D orientation, height gages’ limitations will become apparent. They aren’t capable of measuring cylindrical or spherical objects, or anything else within the 3-D range of measurement.

Still, buyers may want to weigh the pros and cons of using a height gage as a temporary solution to their measuring needs until the company’s economic future looks a little brighter.

The future of height gages

What’s next in the world of height gages? Customers can expect better resolution in the scale and more features built into the gaging processor or display portion, but most believe its unlikely height gages will ever be replaced by noncontact vision measurement equipment, says Schuetz.

"There will probably be some innovation in the way they’re sealed against harsh environments, like dust and moisture," adds Drew Koppelmann, product manager of precision gages at Mahr Federal.

Fowler’s newer gages will feature direct Internet connection capabilities. "By equipping the height gage with a network interface chip, it can connect directly to the shop floor network," explains Fowler. "It looks just like a computer on your network, and you can upload and download information from it, or you can update software."

As for a more distant future, Fowler has a very different take on where height gages are headed. "I think the height gage will meet its end in years to come," he says. "The entire field of dimensional measuring will change significantly as far as what people expect from systems." Fowler predicts that an all-in-one noncontact vision measuring system will someday be developed, eliminating the need for height gages altogether. However, he does note that this innovation will only replace other measuring systems when the price is right. "It comes down to an issue of getting rid of all the hard gaging at a company and replacing it with one fabulous machine," he says. "More than likely, people will plug on like always until they can’t afford not to switch."

Fowler’s sentiments aren’t shared by all, however. "Height gages have definitely found a place in the measurement field," argues Ted Luty, CEO of Dorsey Metrology. "They’ve worked their way up the technology tree, and I would guess that they’ll continue to thrive well into the future."

About the author

Kennedy Smith is Quality Digest’s assistant editor. Letters to the editor regarding this article can be sent to letters@qualitydigest.com.