Alignment -Locating Small Parts

As most operators know, following positions in real-time during an alignment process is the one of most useful tasks you can do with a laser tracker. Sometimes the features are too small to target effectively to place watch windows on a component to track its position in the coordinate system. A trick I’ve used on multiple occasions in locating various small parts or features on components such as assembly jigs or sensor locations on aircraft, is to hot glue push bolt assemblies to assist with positioning components with a laser tracker. This is especially useful when the items are too small to place a 0.500” diameter SMR on or the surface profile will not allow it.

There are two keys to this process that simplify the use. The first is to align push bolts along the two coordinate axis. The second lies with using the thread pitch on the push bolt to your advantage to cut down on the trial and error of positioning. This is described in detail below.

Let’s assume you are using 1/4-20 threads for the push bolts. That represents 20 turns per one inch of travel. Breaking that down for the amount of travel yields the following: One complete turn movement = 1 turn / 20 turns per inch = 0.050 inches. You can break that down further by turning the push bolt one flat of the hex. Since there are 6 flats on the hex bolt, turning the bolt one flat yields a movement of 0.008 inches. In mathematical terms, one flat on a 1/4-20 bolts, moves the end of the bolt -> 1 turn/ 20 turns / 6 flats per turn = 0.008”. This is shown in the figure below.