Improve thread evaluation and UI based on Thread.xlsx (micro screws / NIHS, ISO & ANSI)

[fernando_taboadaLCAK7]

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Bonjour,

Je poste ici une suggestion en anglais afin qu’elle soit lisible par un maximum d’utilisateurs et par l’équipe de développement Autodesk.
N’hésitez pas à me contacter si vous souhaitez des précisions en français.

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Description:

In Swiss watchmaking we manufacture micro screws with very tight tolerances based on the NIHS standard.
We populate Inventor’s Thread.xlsx with NIHS Min/Max diameters (Major, Pitch, Minor) for external and internal threads, and use these values for both the 3D geometry and the thread representation on drawings.

The same behavior is not limited to NIHS – the issue also appears when using ISO or ANSI thread tables with Min/Max values in Thread.xlsx.

Currently, when both Min and Max are defined in Thread.xlsx, Inventor’s internal logic does not correctly use these values to position the thread root lines on drawings. The graphical representation often does not reflect the possible minimum diameter from the standard.

For micro screws, this can lead to wrong under-head sections, broken screws during automatic tightening, and potentially very high production losses, even though parts are fully within NIHS / ISO / ANSI tolerance.

Requested enhancement:

Correctly evaluate and use the Min/Max diameters from Thread.xlsx for:

the thread / tap geometry, and

the thread root representation on drawings.

Add a setting (in thread or drawing style) to choose whether the representation is based on Min, Max, or a derived value.

Clearly document this behavior so users working with standards like NIHS 06-10, ISO metric threads or ANSI threads understand how Thread.xlsx drives the drawing.

UI suggestion (see attached image):

For external threads, show Major / Pitch / Minor Dia with Max/Min values coming from the External Thread part of Thread.xlsx.

For internal threads (taps), show the same fields, this time based on the Internal Thread part of Thread.xlsx.

UI suggestion

The attached image (UI suggestion) illustrates this proposed UI and the link between the dialog and Thread.xlsx.

Benefits :

• Safer design for companies manufacturing their own screws in high-precision fields (watchmaking, medical, etc.).
• Reduced risk of costly scrap due to misleading thread graphics.

Visual example (attached screw drawings) :

The two attached drawings illustrate the problem on a S 0.80 screw:

• Current Inventor formula
  The under-head relief is defined as Ø0.550, and the thread root used by Inventor’s internal formula is about Ø0.561.
  This is what the user sees today on the drawing: a relatively “safe” remaining section under the head.

• Real worst-case according to the standard
  The same screw is shown, but this time the thread root corresponds to the minimum Minor diameter (≈ Ø0.531) defined by the NIHS / ISO / ANSI table, which is still fully within tolerance for the screw manufacturer.
  The effective remaining section under the head is much smaller than what Inventor’s current representation suggests, which can lead to head breakage during automatic tightening (for example).

In other words, the drawing produced by Inventor (image 1) does not visually represent the real worst-case part that we actually receive (image 2), even though it is fully within the specified NIHS / ISO / ANSI tolerance.

Benefits :

• Safer design for companies manufacturing their own screws in high-precision fields (watchmaking, medical, etc.).
• Reduced risk of costly scrap due to misleading thread graphics.
• Better alignment of Inventor with real industrial standards such as NIHS, ISO and ANSI.