There's a reason why I created this
Blender Software Bundle page.
I also use Blender and when you get everything working together correctly, it is VERY nice.
I usually have several example NIF files in my import folder for quick reference when creating swords such as the steel dagger, steel longsword and steel claymore as well as a shield. Once I create my new model from scratch, I import a similar NIF file and then re-position and re-size my model to fit exactly like the imported example. Then I delete the imported example model and export directly to NIF. I usually have no problems this way.
Once I get the NIF file created, I usually consider this a TEMP NIF file that simply contains the meshes I want to import into another NIF file. For example, if I create a longsword, I export my model as MySwordWIP.nif and then copy my example longsword.nif (Bethesda's original) to my final filename such as MySword.nif. I use NifSkope to edit MySword.nif and remove the meshes inside of it. I open another NifSkope window and open MySwordWIP.nif and do a Copy Branch for each model part and do a Paste Branch in the MySword.nif file. Once all the pieces are in the new NIF file, I tweak the collision data/sizing and save the NIF (which is now ready to be used in-game).
LHammonds