Modelling of cast disc

Then go to Edges level and choose three outer edges, and binding Shift on keyboard draw them up. Repeat the action and get:

In Right plan give volume to the disc as in the photo:

Next we create a new object - Tube:

Repeat such actions as with the initial cylinder leaving only 3 polygons. Then select our disc blank and pressing Attach key press on our Tube created. After that switch on points level and with Cut,Weld and Target Weld instruments get the following:

Watch that outside points lie on the lines drawn(IT'S OBLIGATORY!).

Now cut the the hole for the bolt. Cut as in the picture with Cut instrument and delete the polygons marked out in the picture:

Further shape them as in the picture: