Calculating UN thread minor diameter

[nikhil_saldanha]

Hi guys,

I've been looking for a formula to calculate the minor diameter section area for UN(UNC, UNF & UNEF) spec screws to calculate the area mentioned in Table 8.1.5 of MIL-HDBK-5J however none of the formulae mentioned in ASME B1.1 or Handbook H-28 seem to work. After scouting around online I came across the table provided here in EngineersEdge (https://www.engineersedge.com/screw_threads_chart.htm). using the diameters mentioned in this table I was able to obtain the areas mentioned in MIL-HDBK-5J.

Could someone from the EngineersEdge community provide me a set of equations to calculate the minor dia of UN spec threads from the nominal dia and thread TPI.

Cheers.

[administrator]

Webpage has been updated to show thread graphics sufficient for an equation.

https://www.engineersedge.com/screw_threads_chart.htm

[kadequitzon]

Thanks, It's super easy