Final answer:
The fraction used for shrinkage in a 22 1/2 degree bend depends on the specific context and guidelines of the trade, such as pipe fitting or electrical conduit bending, and is not provided in the given information.
Step-by-step explanation:
The fraction used for shrink in a 22 1/2 degree bend is a specific value that may vary depending on the context of the task—such as electrical conduit bending, plumbing, or metalworking. However, the fraction commonly provided for the shrinkage factor in such bends is not evident in the information given.
Typically, in pipe fitting or electrical conduit bending, a shrinkage multiplier is used to compensate for the shortening of the conduit or pipe on the bent section. This multiplier would normally depend on the bend angle and type of bend; for a 22 1/2 degree bend, a shrinkage would be a particular fraction of an inch per inch of bend.
If working with specific materials or in a particular trade context, this value should be obtained from the technical guidelines or a manual related to that trade. As the information provided (1.90 × 10-3, 1 mm shrinking, etc.) does not directly pertain to shrinkage for a 22 1/2 degree bend, I'm unable to give an exact fraction without further context.