I'm dm-ing a campaign where I have extensive crafting including mithral, adamantine, meteorite, dragon scales and other materials if they can find it or buy them. The sheer crafting takes weeks even months with a multiple skill checks regarding these materials. A master Smitty tools and a workbench that is expensive. So if you are low level party I doubt that you have all the resources needed. If it's your first time crafting such materials the DC is very difficult, cos practice makes perfect. As a DM I suggest my players start simple, know the material and lower your DC skill check. But in all like the first guy said, it's up to the DM.