hi everyone,

I know very little about machining and I want to learn more. I asked a machine shop to make a part. It has a thread to connect with another part. Of course another part has thread too. My idea is I can use my hand to have enough force to turn the part into another part. But the thread is too tight to turn by hand, I want to know how does the machine shop will do to make the thread lose a bit so that it can turn in by hand completely. I want to know what will the machine shop do on the part to make the thread more smoother? thanks

If the thread was put on the part with a lathe the threads can be "picked up" again and a few thousandths can be removed. If the two mating parts can screw together the threads might just need to be polished or cleaned up, it might have a burr.
 If the part was threaded with a die most die's are adjustable.

Aside from the above advice there is one thing that is quite common with tight threads is there is root tip interference. This can be helped by taking a light file cut on the tips of the male thread or on future parts by an oversize tap.
If the interference is on the female thread tips it is harder to take down the tips. Interference from Internal thread tips can be corrected on future parts by using a slightly larger drill bit.