Aeglos, welcome to the Downs!
You started a very interesting thread, and asked a good question:
And if the valar saw the elves making weapons why didnt they stop them, because there was no need for it, and could only be used to bad things like violence and murder. So what do you think?
My view is that the Valar were content to let the Noldor govern themselves, and only intervened when things got out of hand, which they did in the case of Fëanor, who threatened violence and murder with a weapon he made.
Under Morgoth's influence, as well as making weapons, Fëanor spoke out against the Valar. Fingolfin brought up this matter at a meeting before their father, Finwë, asking what he was going to go about Fëanor, pointing out that he (Finwë) was one of those who originally spoke before the Elves, urging that they go to Valinor, saying that if he was still of the same mind, he had at least two sons (Fingolfin and Finarfin) to support him.
Fëanor turned up armed, accused Fingolfin of usurping his place, and threatened him with his sword. When Fingolfin left, Fëanor followed him, and again threatened him with his sword, this time saying that he might kill him if he usurped his place. '
See, half brother! This is sharper than thy tongue. Try but once more to usurp my place and the love of my father, and maybe it will rid the Noldor of one who seeks to be the master of thralls'.
Fingolfin left without saying anything in reply.
I don't think anyone here would be surprised that the Valar then intervened in an incident where the King of the Noldor's eldest son turned up armed at a peaceful meeting, and twice threatened his brother with a sword, the second time implying that he might kill him. Also, Fëanor's language could be seen as particularly insulting, calling the Noldor 'thralls', i.e. slaves, implying that his people were slaves, presumably of the Valar.
Even when it was found out that Melkor's influence was at the back of what happened, the Valar, rightly, said that Fëanor was still responsible for his actions and would be exiled. At least Fëanor didn't give the excuse of 'Melkor made me do it!'
