U/S Threads in 17-4 after H/T - H900

[dmass]

I'm currently working on improving a process to eliminate reworking threads on 17-4 parts with internal threads after they have gone thru the H900 H/T process. They are mostly tapped holes. My plan is to do some testing using larger class taps. Any info anyone could provide to me to shorten my testing/developement time would be great.

 

[israelkk]

All PH steel shrink during the heat treatment. The shrinkage can be up to 0.01 mm/mm. Therefore, the larger the part or the dimension the larger the dimensional change. What is the thread diameter and accuracy? You can not predict the shrinkage unless you test each batch of material and tap each batch to a different tap dimension which is impractical.

To my opinion you will have to re-tap the thread using a tap material that can tap the 17-4PH at the H900 condition.

 

[NickE]

Use a nice carbide, coated tap. and Good Quality sulfur bearing cutting oil. After you go to H900. 17-4 etc.. dont get all that hard ever.

You'll likely not make capability heat to heat as israelkk says.

 

[dmass]

Thanks for the input. israelkk - the thread sizes range from 1/2" to 1" class 2B.