The first turret used on the Tiger B was inherited from the VK4502 project. The turret seating ring on the hull roof was specific to this turret.
The ring was flat and its outer edge was welded to the hull top. The opening for the turret was 1940mm in diameter, and it was cut after the ring was fixed in place; therefore the inner edge of the roof armour was flush with the inner edge of the ring and could not be welded [3, see photos on page 112] [2, see photo in Chapter 6] . To add strength the ring was held to the roof by rivets (marked in this diagram).
The ring was made of 4 segments welded together; the weld lines (shown here) would have been very difficult to see on close examination because the surfaces were ground flat after welding.
There were support braces welded under the hull roof of the Tiger B. I don't know their shape in vehicles with this turret, but in all later vehicles they interfered with the parts of the turret ring. Assuming that the braces were always the same, the rivet positions at extreme left and right could not have been used. Because the holes were bored after the ring was welded to the hull, I assume these holes would not exist.
The rivets were specified as 16 x 80 DIN 302 [1] which is a recessed-head rivet 16mm in diameter. The holes for the rivet, as shown here, were 17mm wide. The rivet head must not have been allowed to protrude above the surface of the turret ring, because this would have interfered with the watertight seal of the turret.
For attaching the turret, bolt holes of 24mm diameter were cut through the ring and hull roof. Once again, two positions would be unused if the internal braces were the same as in later vehicles.
To help align the turret when lowering it on the hull, it was provided with 3 locator pins on its underside. Holes for them were drilled in the turret ring. At 30mm diameter, the pins could not accidentally enter the bolt holes; their own holes were apparently 40mm wide.
The hull roof plate, which was 40mm thick, was made of 3 butt-welded plates. As you can see here, the weld lines were placed to avoid any of the holes in the turret ring.
There were two additional holes that I cannot draw because I have not enough information about them. They are for the inflator tube and drain of the sealing system. I know only that they were located in the forward left quadrant of the ring.
On 29 November 1943 a change was made to the design drawing for the turret ring. The opening in the hull roof plate was made 30mm wider than the opening in the turret ring. This change was probably to simplify the manufacture of the tank. The roof plates were individually rough-cut before being welded together; now, when cutting the 1940mm hole in the seating ring, there was no longer any need to cut through the 40mm roof armour as well.
On 30 December 1943, another change was made to the diagram. Twelve steel blocks were welded under the new overhang of the turret ring. Both of these changes can be seen in this view of the ring as seen from below.
I don't know when these changes were introduced to the production line; the turret guard ring, first drawn on 14 January 1944, was not introduced on new tanks until April. A photograph shows these changes on a hull that has a turret guard ring, so they did coexist with prototype turrets.
[1] Workshop drawing 021 B 49501 U28 : Tiger B hull top
[3] Der Panzerkampfwagen VI und seine abarten, Walter J. Spielberger, Motor Buch Verlag