Hi Dan,
Unfortunately, I don't have an example BOM. However, I think you will find the sample that comes with Crystal Reports very helpful. Open the Hierarchical Grouping sample report and it demonstrates how create a employee table and showing the relationships between different employees and how to properly indent the data. This should give you a good starting point for modifying it to report from your parts database tables.
If you need more in-depth information about creating hierarchical reports, I cover it in Chapter 3 of my Encyclopedia book. You can find out more about my books at
Amazon.com
or reading the
Crystal
Reports eBooks online.