Custom thread type not appearing in Thread dialog – NSP (National Straight Pipe)

[CcampbellYCLST]

I'm trying to add NSP (National Straight Pipe) as a custom thread type in Inventor 2026 by adding a new sheet to the Thread.xls file located at: C:\Users\Public\Documents\Autodesk\Inventor 2026\Design Data\XLS\en-US

I modeled the sheet after the existing NPT sheet — same column structure, I S in cell A1 (since NSP is a straight thread), and a matching Sort Order in D1. The sheet tab is named NSP. However, after saving and restarting Inventor, the thread type does not appear in the Thread dialog dropdown.

Has anyone successfully added a custom pipe thread type? Is there something specific Inventor requires beyond the sheet structure — such as hidden identifier cells, specific merge patterns, or formula-based columns?
I also noticed GOST Self-tapping Screw Thread and DIN Wood Screw Thread are not in the drop-down, and they are in the original xls file.
See attached file, NSP is all the way at the end.

@johnsonshiue 

[hollypapp65 · Accepted solution]

Change the "S" to "Q".

And something wrong in the table.

Maybe copy and edit BSP straight table instead of the taper table.

[hollypapp65 · Accepted solution]

Try this one.

[CcampbellYCLST]

Thank you! it works. What was the problem? I copied the NPT to start with, but this looks completely differnt then the NPT sheet.

[hollypapp65]

Need to use straight thread table.  IV don't check table format.