What is the dimension center to face of a 45 degree 5D elbow?

The dimension from the center to the face of a 45-degree 5D elbow typically refers to the centerline radius of the elbow. For a 5D elbow, the centerline radius is five times the nominal pipe diameter (D). Therefore, the center-to-face dimension for a 45-degree 5D elbow would be calculated as the centerline radius plus half of the diameter of the pipe, which is 5D + (D/2) = 5.5D. This can vary slightly depending on specific manufacturer standards, so it's always best to consult the technical documentation for the specific elbow being used.