Threading 4140 HT question?

[jeremy13]

For right now the job will be done on a manual lathe 7.5HP I have 3 main parts to make 30 of each witch screw together. All the threads run in to a shoulder. I'm going to cheat with the left hand threading bar on the ID threads.
The parts are
4140HT 12tpi ID thread
6061 OD 12tpi thread
6061 ID 18tpi thread
316SS OD 18tpi thread

Tomorrow I'm heading to Bass Tool to get me some threading inserts they will be laydown 16ER and 16IL if they have them. Now the question is witch coating should I get, TiN is a standard for steel. How about the other type of coatings? Doesn't aluminum like to stick to TiN inserts?

[Toolguy]

Any coating will work. Aluminum will stick to TiAlN, Titanium Aluminum Nitride if it gets hot enough. It is highly unlikely you will ever reach that kind of temps with a threading operation on a manual lathe, especially with cutting oil. The TiAlN is a lot harder than TiN.