Many people worry about the temperature drop in multiple blades. Lets look at what we are doing and see how that really works:
When we HT the steel, we need to get it to a certain temperature to allow the ingredients to go into solution, for the purposes of this article, lets say that is 1500F. Once at that temp, it needs time to allow the carbides and alloy ingredients time to go into solution. For this we will say 10 minutes. If you heat ten blades to 1500F and hold them at that temperature for ten minutes, then all that is needed to happen has happened. Longer time won't make much difference as long as the temperature does not go HIGHER. Now, when you start opening the oven to make the quenches, the temperature drops and then rebounds a bit. For our example we will say it drops to 1400F. If the temperature does not pass the critical point, there is no change to the steel, so any amount of time above 1350F will not affect the steel, once it has had enough time at 1500F. A look at the Isothermal Transformation Diagram of simple hypereutectoid steel will show you that it is the point at about 1000F that is the crucial spot in getting the austentitic steel to convert to martensite. As long as the individual blades do not drop below about 1350F, you have about an hour before they start to transform into pearlite. During that time the austenite is still a solid solution and will sit quietly until its number is called.
So, if you use safe procedures, and take your time ( but don't waste any either), and the oven does not drop below 1350F.....you will be fine....as long as the quenchant can drop the blade below 1000F in less than one second once the blade enters the quench.
Transfer from oven to quench tank should be a smooth and reasonable quick movement, but the blade does not normally cool enough during that short interval to matter either. In multiple quenching, since the blade may already be 100-150F lower than normal, do it as quickly, but safely, as possible.
Practice opening the oven, removing a blade, and closing the oven many times with a cool oven first. Having the procedure down is important in multiple blade batches. Monitor the oven, and let it rebound a bit if it starts getting near 1350F. An assistant to open and close the oven door , while you extract the blade and quench it, would be a good idea.
Once fully austenitized at the target temperature, it does not matter how much ( within reason) the steel see-saws between 1350F and the target temp. If it does not go higher than the target, it will not grow larger grains; and if it does not drop below 1350F, it will not convert from austenite.
Hope this helps.