3/8-16 NC 5IF thread

[gcode]

We are builing a part from a B/P that datesd back to 1970

There is a callout for a 3/8-16 NC 5IF  

Google says this is an interference class thread but I have no idea what size tap to buy

My tool supplier says an H5 will work

Does anyone have any experience with this

 

 

[DUM1]

I see that you can buy plug gauges for that but I haven't seen a tap  , thread mill?

the same description / call out is in the machinist 23 edition hand book ... good luck with that G

[Colin Gilchrist]

14 hours ago, gcode said:

We are builing a part from a B/P that datesd back to 1970

There is a callout for a 3/8-16 NC 5IF  

Google says this is an interference class thread but I have no idea what size tap to buy

My tool supplier says an H5 will work

Does anyone have any experience with this

 

 

Class 5 Threads FED H28 Handbook > A11

The first thing I searched was "NC5 IF Thread", which took me here:

https://www.engineersedge.com/hardware/class_5_interferencefit_threads_ansiasme_b112_13195.htm

Then I searched "FED H28 Handbook", and found it in PDF Form. Published in 1957. If you have trouble finding it, let me know and I’ll email you the PDF I found.

basically, the IF threads have a bigger minor on the Internal, and a truncated crest on the External, to allow for plastic flow of the metal, when torque is applied. The external thread should have a pitch diameter which is in slight interference with the hole.

You are cutting the ID Thread, so "normal 3/8-16” tap, hit the Pitch Diameter, and drill the Minor Diameter oversized. (0.314) and call it a day…

 

 

 

[gcode]

Thanks Colin

We ending up running a OSG Hy Pro 7 3/8-16 H5 tap