Comparator Stand Guide

What is a Comparator Stand?

Comparator stands are used for measuring the heights or widths of small parts such as the heights of roller and bush, the width of the bearing ring and so on. Most of the dial comparator stands are handy, compact and portable, which is why they have always been popular for machine shops and the production lines in the automobile and aerospace industries for sophisticated parts. The bench type of dial comparator stands is often considered the most common height gage because parts can be brought to it easily. Later we will take a look at the structure of the bench dial comparator stands.

There are a variety of comparator stands that varies in sizes, levels of accuracy, and materials. It is essential for you to entirely understand the capabilities of the comparator stands and the use to achieve quicker, simpler and more accurate measurements that in turn translate to less cost for maintaining and adjusting. 

Structure of Comparator Stand

Bench dial comparator stand consists of three basic parts, which include the indicating dial, the post and arm assembly, and the base with the locating surface that are designed for supporting the parts. Test Stands also have the indicator, post and arm assembly, but they don’t have the locating surface. Test dial stands can only be utilized with the surface plate. 

With that said, bench thickness height gage also consists of a base with locating surface for parts and the indicating element. However, it has no flexibility within the arrangement of post and arm assembly. Understanding the structure differences and features of different components among different height gages can significantly help you to select a better comparator stand to meet the needs:

● Base:

On most comparator stands, particularly the stands designed to measure relatively large parts, the base plays an important role as the reference surface or locating surface. Typically, they are made from granite or steel such as cast iron. To reach more ideal accuracy, it is recommended to mount a steel or ceramic anvil onto the base of the comparator stand.

● Anvil:

Compared to the base, anvils are smaller components that can be designed and manufactured with tighter flatness tolerances, which are typically only several microinches over the flat surfaces. Many advanced anvils have grooves that are machined on the reference surface, which can remove the dirt or chips away from the target parts. The serrations can reduce the contact area where the contamination might introduce errors. For very tiny and light parts, the serrations can prevent the air from getting under the tiny parts and interfering with the reading. In some comparators, anvils can also provide a wringing surface that creates an ideal environment for extremely critical measurements. Compared to the bases, anvils are easier to maintain clean and to adjust to squareness with the indicating element.

● Post:

Post is also a vital component in comparator stands. Larger and heavier posts generally have more stability but less variability. Many posts have helix grooves to get rid of dirt, preventing contamination from getting between the post and the clamp of the arm. The dirt might be the key resulting in slop and part wear of the height gages.  The post is essential to support the arm which prevents the arm from dropping whenever you loosen the clamp when adjusting and damaging the components. It is recommended to mount locking rings or other locking mechanisms on the post. A rack-and pinion drive can help with positioning the arm even when it is heavy. With locking mechanisms, the weight of the heavy arm will not consistently rest on the screw. In some comparator stands, a post might be a slide that removes the rotation of the arm in the plane. In this arrangement, the setup will be simpler, but the arm should be raised up or lowered for measuring different heights of parts.

● Dial Indicator:

The indicating elements of the comparator stands are often the dial indicators. They can be mounted vertically and be positioned and locked in any location. The sliding rings which are incorporated with the locking screws allow the dial indicator to swing to another side. Sliding rings also serve as the safety device that ensure the beam will not drop down accidentally. Beam can be finely adjusted for final setting of the dial indicator. On the dial indicator, the lever which can be lifted by hands can raise and release the spindle to contact the target parts. 

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