Occasionally I've needed a Buttress Thread and I haven't found anyone who's got a spreadsheet of the thread data. Well I finally sat down and made a spreadsheet that can be added to the threads.xls file in Inventor. If you place this as a new tab in the thread spreadsheet it will show up at the bottom of the selection box for the thread type in Inventor. You can change the sort number in the upper left corner to make it show up where you want it in the list. This is not a complete listing of the "preferred sizes" but it covers a good portion of them. I calculated the numbers and entered them so there may be a type-O or two. Please verify the data. I also attached a spreadsheet that can be used to calculate basically any Buttress Thread based on the values you find in the machinery handbook....you'll have to look a couple numbers up an put them in the sheet but you can then add any buttress thread you want/need to the table.
If you have any questions about how to add the threads or use the calc sheet let me know