How do I extrude inward towards Z axis? Trying to make an auger

[distantkitty (Mike T)]

I’m sure this is easy, I just cant figure it out. I’m trying to extrude towards the Z-axis all the way up the spiral. I can extrude in X and Y directions independently, but can figure out how to extrude inward.

Thanks!

[akilli (Ethan Gross)]

Use Scale NU on the curve for just the x and y directions to get the inside/outside? curve, then Loft between the original and scaled curve.