Height Gages Explained
Height gages, or gauges, are an important piece in the vast array of inspection and measurement tools. In simple terms, a height gage is a bench top tool commonly used to either measure vertical distances or make repeated markings on a part. They are much more capable than calipers, but not as complex (and expensive) as a coordinate measuring machine (CMM).
Let’s take a look at the main characteristics, types and best models.
As seen in the image above, height gages are composed of several different parts. Although different types feature different components, some of the main body parts are consistent across every gage:
Beam: The vertical column on which the slider moves to take measurements. On Vernier height gages, the beam typically features two engraved scales (imperial and metric) that take the main measurement. More sophisticated, digital gages feature a dual beam that facilitates the slider movement.
Base: Height gages feature a solid base designed to give stability to the vertical columns and keep it perpendicular to the table’s surface. A solid base is an extremely important feature, especially when it comes to oversized Vernier height gauges.
Slider: A unit connected to the beam that slides up and down. The sliders on Vernier gages feature a scale used to take measurements with an accuracy of 0.001” while electronic gages feature an electronic measuring slider mounted on the beam.
Fixing device: The fixing device connects the slider to the scriber, test indicator or touch probe. Most height gages come with a scriber by default. It makes it easy to scribe a line, particularly in layout dye, on a part at a specific height.
Types of height gages
Similar to micrometers and calipers, you can also get height gauges in Vernier, dial and electronic types. Here are the main differences between the types.
Vernier Height Gage
This type of height gauge is available in sizes from 6” to 6’ in height. Relatively simple to operate, their main advantage over other height gages is the range of sizes they come in, meaning they can be used to accurately measure a wide range of workpieces. Typically, both imperial and metric scales are shown on the beam.
Dial Height Gage
This style of gage is generally only available in smaller sizes (under 12”). The dial makes reading the device easier than a Vernier scale.
Digital Counter Height Gage
Digital counter height gages with dial and dual-digit counters decrease the time needed to lay out a part. Not only is the dial easier to read than a Vernier scale, but the dual-digit counters allow one counter to be set at the reference datum and the other to be used as a floating zero.
Electronic Height Gage
Although technically considered height gages, their level of sophistication almost puts them on the same level as CMMs. Depending on the level of accuracy and features, electronic height gages can be divided into three different groups:
- The first group has accuracies similar to mechanical height gages. Generally, gages belonging to this category will have inch/metric conversion, absolute zero and floating zero, and data output.
- The second group includes all the features from the first group, however the accuracy of these tools is exponentially higher. Gages in this group may also have additional features, such as tolerance setting, ID/OD measurement, max./min., TIR and probe compensation.
- The last group has all the features of the second group and a higher accuracy rating. Most height gages in this class will have air bearings, a motorized touch probe, the ability to generate and store part programs, and a computer interface. They also can measure a part feature in two dimensions by rotating the workpiece.
As you’ve probably gathered from the information above, the variety of height gauges is pretty broad. The most sophisticated models on the market have very similar characteristics to 3D CMMs. Their price, however, inevitably reflects that level of sophistication. Luckily, there are also helpful models that will cater to the most common needs without hitting your wallet too hard.
Here are some of our favorite, “affordable” models:
Starrett 3259-12 Stainless Steel Dual Post Dial Height Gage, 0-12″ Graduation Range, 0.001″ Graduation
The only dial height gage that made it on our list. The dual-beam provides increased movement, smoothness and stability for consistent measurements and the two separate digital counters can register upward and downward travel. Although less accurate (0.001” graduation) than its electronic counterparts, this is a solid and accurate model.
Easy to read and accurate (0.0005” graduation), this is an excellent tool at a great price, considering it’s a Starrett. The included scriber, used to mark position on the workpiece, is steel for hardness and durability. The round nose of the scriber cuts clean, sharp lines with smoothness and less pressure and can reference zero from the bottom of the base to get the full usable range.
If you are looking for something more sophisticated, Mitutoyo has the solution for you. This height gage has an electronic microprocessor providing the ability to preset a reference height at any position as well as to set a temporary zero position and return to a true zero reading. The featured model allows for measurements up to 12”, but larger models are also available (and currently on sale!).
This accurate electronic gage is precise to 0.0005” and can measure parts up to 18”. The hand-operated feed wheel raises and lowers the gauge on the beam with smooth, even travel, and is selectable for coarse or fine feed. The gage has a hold function to freeze recordings on the display as well as a zero-setting function.
Before you start measuring
Although measuring or marking your parts with a height gage is a pretty easy and straightforward process, there are some preliminary steps that need to be taken before getting started.
First of all, make sure you have a surface plate and gage blocks to validate all your measurements. Another important step is to clean both the working platform and the base of your gage before you start working on it. Use denatured alcohol to clean the surfaces and wipe clean to remove any dust oil or other contaminants that may cause the gage to stick to the plate. Last, but not least, check that there’s no debris between the surfaces. To do so you’ll need a test indicator. Mount a test indicator to the scriber and bring the indicator to the surface or reference part. Zero the gage and then gently press down on the corners of the base. If the indicator moves, the surface is not level and should be until a smooth surface is obtained. Once these preliminary steps are taken, you are ready to start measuring your part.
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