A jig is a device usually used to help in creating a replica of an object during mass production of parts or tools, in alignment terms; jig simply means a device that can help in the setting of apparatus for alignment in a way to ensure the accuracy of the parts being aligned.
Most times during pipe fitting device like that can be used in holding the two pipes together before welding can be carried out on the space between them. The same method is done when it comes to pipe flanges and machine alignments, a device is usually fabricated for the purpose of fixing dial gauges such that their knobs can be touching the flanges of pipes and machines to be aligned, in such case one side of the flange is fixed with the jig while having the dial indicators fixed or screwed to the jig and the knob of the dial indicators will be touching the other flange to be aligned.
There are many designs of alignment jigs, the design for each work depends on the specification of the wright handling the job. When the dial indicator will be more than one, the design of the jig will be complex, the reason is because of the screwing anchors needed for the various dial gauges.
If you wants to form jig for a single dial indicator, below are the steps to follow:
Measure the gap between the two flanges, and ensure the jig metal size can accommodate the initial deviation in the two flanges.
Take a drawing or sketch of the arrangement required for proper alignment of the flanges and create the jig to respond to your design.
Fixed the fabricated jig on the side of the flange that has been alignment already or where more jobs may not be carried out, this is mostly on the pipe flanges but situation may change where fixing at machine flange may be the only object.
Aligning machine mostly exist by aligning the machine flange to the pipe flange and then coupling of the two flanges.
After every setup run the pre-alignment test to check the accuracy of your data records before proceeding to the proper alignment.