Wheel Building - Spokes Question

I would guess that you'd find it really difficult to screw the nipples past the end of the thread.

Either:

• you have screwed past the end of the thread and you've stripped some of the threads from the nipple (softer than spokes so thhats where the threads get stripped).
  
• most nipples have an unthreaded portion of about 2-3mm inside the spoke end and you may have just used up this unthreaded portion without doing any damage.
  
  

If you have stripped the threads a littl, you are more likely to have the rest of the thread stripped than you were, but there may still be about 8mm of thread gripping the spoke and that may be enough if you're not a heavy rider. All depends how many spokes you have. 32/36, may be ok, less than 32 I'd be starting again with the correct spokes and new nipples.

If you have any spare nipples, check inside the end to see if they have an unthreaded recess.