The first thing you want to do is to set your cursor to the middle of your hammer (represented by a cylinder in my case).
Then add your spike somewhere around it. To create several spikes around the edge, you have 2 methods:
Duplicate your object, rotate it around the Y axis by XX degrees and repeat the operation.
But this one is harder to modify as you have to delete you cube and realign them if you want to change its shape. The second option use an array modifier which is more adequate to the situation.
2-Array modifier Same beginning with the cursor, but create an empty object that you want to leave at the cursor position. This time, don't forget to move your object in edit mode instead of object mode so that the geomtry center point remain at the cursor location.
Add an array modifier to your object and deselect everything
Select the empty object as object offset and change the count
If nothing is shown, this is normal, just select the empty object and rotate it around the Y axis, your spikes should start moving.
In the example, I rotated it by 45° with 4 new cubes 4*45° = 180°, the last cube is rotated by 180°. Hope it helps
You can also use a particle system to distribute objects on your object surface. This method has the advantage of working on any kind of surface, not just circular ones.
Create the spike object separately, set its origin to the cone bottom face and setup its material. You'll map the spikes to vertex positions, so select the hammer, go into edit mode and use loop and slide to create a new edge loop right in the middle of the rings onto you're going to place the spikes.
Assign the vertices to a new vertex group.
Create a new Particles System. Select Hair, set the size to 1, check Advanced, Emission to Verts and uncheck Random.
Lower the number of particles, set the size to 1, and set Vertex Groups > Density to the group you've created. Check Rotation and make sure it's set to Normal.
Set Render > Dupli Object to the spike mesh and check Rotation (which I forgot to check before taking the screenshot!). To control the size of the spikes you can either set the render Size to 1 and resize the spike object to the correct size or tweak the size setting.
If the spikes don't protrude correctly from the face, select the spike object and rotate it 90º in one of the axes until it's right.
Now tweak the number of spikes to the number of vertices. To further space them by divide the number of vertices by 2 or more.
In case you need the spikes as real meshes you can Convert the Particles to real meshes on the Modifiers tab.
If you're intending on converting the particles to meshes you can also do nice tricks like duplicating the edge loop on the hammer so it's not connected to the geometry, assign this loop to the spikes vertex group, dissolve the original loop and subdivide the new unconnected loop at will to get more vertices for particles placement. Don't forget to assign the new vertices to the vertex group. Once you convert the particles you can delete the edge loop so your hammer won't have any extra vertices at all.