[Doubt] Lathing threads for oilwell equipement

[Bryan7]

Hello guys, I am new here. I have a concern related to lathing threads for the oil industry I hope some of you have experience with that and can help me.
You´ll see, I am currently doing a research about the machining and repairig of threaded connections in equipment used in drilling wells, specifically API connections.
I have gather a lot of information about machining this types of threads in lathes, I mean its fabrication process, but I have problems trying to figure out how can this treads be repaired, I know there are problems that can be repaired (a lot of shops offer this service) but I really don´t know what problems can they fix and how.
I ask this because I know in this industry every tool has to be within certain parameters to operate and being the lathing proccess a sustractive manufacturing process, I wonder what´s the limit of the wear they can fix. (if there is a discontinuity in the thread can they weld steel and lathe again? things like that)
If you have experience working in this industry or you know books, sources of information I would really apreciate if you can reply. I haven´t found relevant information by myself.
Thanks for your time, I hope you have a good day.

 

[4GSR]

The only way to repair a Rotary Shouldered Connection is to cut it off at the shoulder of the connection and cut a new connection. On drill pipe, you can chase the thread to cleanup the profile but doing so, the shoulder has to be moved back to proper stand off. Again, just so much is allowed for chasing threads on DP. If it exceeds this, the connection is scrap. New connections can be welded on the pipe body, but is it really worth it? IMO no. On Rotary Shouldered connections used on drill collars, cross overs, stabilizers, reamers, etc. Those connections generally are cut off and re-threaded. Can't take chances of cracks in the thread roots, that's why they NDE threads.

Ken

 

[Bryan7]

The only way to repair a Rotary Shouldered Connection is to cut it off at the shoulder of the connection and cut a new connection. On drill pipe, you can chase the thread to cleanup the profile but doing so, the shoulder has to be moved back to proper stand off. Again, just so much is allowed for chasing threads on DP. If it exceeds this, the connection is scrap. New connections can be welded on the pipe body, but is it really worth it? IMO no. On Rotary Shouldered connections used on drill collars, cross overs, stabilizers, reamers, etc. Those connections generally are cut off and re-threaded. Can't take chances of cracks in the thread roots, that's why they NDE threads.

Ken

Oh I see, I really apreciate your answer, you have given me a lot of info. Thanks