From BlenderWiki

Spin

Use the Spin tool to create the sort of objects that you would produce on a lathe (this tool is often called a “lathe”-tool or a “sweep”-tool in the literature, for this reason). In fact, it does a sort of circular extrusion of your selected elements, centered on the 3D cursor, and around the axis perpendicular to the working view…

Here are its settings:

• The point of view will determine around which axis the extrusion spins…
• The position of the 3D cursor will be the center of the rotation.
• The Degr numeric field specifies the angle “swept” by this tool, in degrees (e.g. set it to 180 ° for half a turn).
• The Steps numeric field specifies how many copies will be extruded along the “sweep” (exactly as with Extrude Dup above…).
• The Clockwise toggle button control the direction of rotation (as you might have guessed, clockwise when enabled and counter-clockwise otherwise).
• The Keep Original button, when enabled, will keep the original selected elements, as separated islands in the mesh (i.e. unlinked to the result of the spin extrusion).

Examples

A Glass

Glass profile.

First, create a mesh representing the profile of your object. If you are modeling a hollow object, it is a good idea to thicken the outline. (Glass profile) shows the profile for a wine glass we will model as a demonstration.

In Edit mode, with all the vertices selected, access the Editing context (F9). Set the Degr numeric field to a full 360° sweep.

We will be rotating the object around the cursor in the top view, so switch to the top view with 7 NumPad.

Glass profile, top view in Edit mode, just before spinning.

Place the cursor along the center of the profile by selecting one of the vertices along the center, and snapping the 3D cursor to that location with ⇧ ShiftS » Cursor -> Selection. (Glass profile, top view in Edit mode, just before spinning) shows the wine glass profile from top view, with the cursor correctly positioned.

Mesh data – Vertex and face numbers.

Before continuing, note the number of vertices in the profile. You’ll find this information in the Info bar at the top of the Blender interface (Mesh data – Vertex and face numbers).

Spun profile.

Click the Spin button. If you have more than one 3D view open, the cursor will change to an arrow with a question mark and you will have to click in the window containing the top view before continuing. If you have only one 3D view open, the spin will happen immediately. (Spun profile) shows the result of a successful spin.

Seam vertex selection.

The spin operation leaves duplicate vertices along the profile. You can select all vertices at the seam with Box select (B) shown in (Seam vertex selection) and perform a Remove Doubles operation.

Notice the selected vertex count before and after the Remove Doubles operation (Vertex count after removing doubles). If all goes well, the final vertex count (38 in this example) should match the number of the original profile noted in (Mesh data – Vertex and face numbers). If not, some vertices were missed and you will need to weld them manually. Or, worse, too many vertices will have been merged.

Vertex count after removing doubles.

Specials menu.

Merging two vertices in one To merge (weld) two vertices together, select both of them by ⇧ ShiftRMB clicking on them. Press S to start scaling and hold down Ctrl while scaling to scale the points down to 0 units in the X, Y and Z axis. LMB to complete the scaling operation and click the Remove Doubles button in the Buttons window, Editing context (also available with W » Remove Doubles). Alternatively, you can use W » Merge from the same Specials menu (or AltM). Then, in the new popped-up menu, choose whether the merged vertex will have to be at the center of the selected vertices or at the 3D cursor. The first choice is better in our case!

All that remains now is to recalculate outside the normals by selecting all vertices and pressing CtrlN and validating Recalc Normals Outside in the pop-up “menu”. At this point you can leave Edit mode and apply materials or smoothing, set up some lights, a camera and make a rendering. (Final render of the glasses) shows our wine glass in a finished state.

Final render of the glasses.