If you have an oven that you can set at 400 degrees F., The oven must be at temperature before you start and the rule of thumb is that you must put your piece in for 1 hour for each inch of thickness. If your plate is 1-1/4 " then you need the same amount in time as well. 1-1/4 hours. I would give it an extra 1/4 hour to be sure that it is heated evenly. The torch method is inconsistent and your piece will have different temps throughout. That can lead to warping or distortion of the plate. You can buy cans of liquid nitrogen that spray just like paint spray cans do. A .001 to .0013 is plenty for an interference fit at that diameter. You need to have everything perfectly set up to assemble because you will only have a very limited time to insert it. We are talking in seconds here. As soon as the materials come together it takes only a few seconds before they match temperatures. The bigger the temperature difference the longer you have to fit it. Too much interference will take those seconds away and you will be stuck in the same situation where you must force it through. Remember that if you take the plate out of the oven and lay it on a solid surface the contact will suck the heat out of the plate very quickly. Put down some type of heat resistant insulation material that will slow the transfer down before you take it out of the oven. We used to put pins in the freezer for a few hours before using the nitrogen spray. It is really a 2 person job. One takes care of the hot plate while the other keeps the nitrogen spay going on the shaft. Once the plate is laid down then the pin must go in right away. Have a mallet handy so you can push it in as fast as you can.