My sorry but why you use this oven ? you need only heat to the place that the bearings must go in or go out , a heat gun do this job in one-two minutes
I have see many others that they use oven i cant understand for what reason what they do chainsaws with potatos or chainsaws chocolate cakes.
you want cold case but hot inner race bearing when you put the shaft into the bearings and when you try to close the case , this because if you have hot case you maybe loose the corect place than the bearing must be , the cold case keep the bearing in place and the hot inner bearing race help the shaft to go eaiest to the bearing.
The best way to heat the inner race and keep the other thinks cold is to use a soldering iron or a heat gun with small nose.
again my sorry