Subtraction Function is not subtracting

[Anonymous]

Hi 

Ive created a spiral strair case in auto CAD, and i can do everthing perfectly until i have to subtract the helix shape from the solid stair case.

i want to subtract the yellow helix solid with the stair.

i follow the steps for selecting both the solid then pressing enter, 

then selecting the yellow helix enter again and then selecting the stairs and enter again.

not sure if i missing a step or its just glitching?

if anyone can help would much appreciate it.

[maxim_k]

Welcome to Autodesk Forums!

Hi,
Your workflow should be:

Select the objects that you want to keep, press Enter, then select the objects that you want to subtract. Than hit Enter for the last time.
Objects in the second selection set are subtracted from objects in the first selection set.
Your first step confused the command.

Maxim