Problem With Threads

[SĤ𝕒∂όⓦŁ𝔸ŜєR]

Hi everyone,

I'm having a problem with both the internal and external threads on hollow aluminum tubes. I can't figure out which measurements to use for the internal ones and Which for the external ones, especially on the part that acts as a cap. For example :
If I have an aluminum tube that measures 4 cm from end to end, once the external thread is threaded, how do I screw on the other part,
The internal threaded cap?
That's all.

​

SĤ𝕒∂όⓦŁ𝔸ŜєR​

 

[SĤ𝕒∂όⓦŁ𝔸ŜєR]

Problem solved 100%, if I had waited for you, I would have been in trouble!!!