In your 3rd picture, click on the blue dimension that says 3.07 and then when the edit dialog box appears, click the lock symbol. This will lock that thickness value down for you so it won't change when you adjust your other dimension from 48 to 53. You can also do the same thing on the bottom of the part.
thank you. I tried it before but then the conical bottom part became flat. I thought to take the dimension from nut to the top of the bottom surface and locked it, then click on 48 and choose to extend to bottom and it worked.. had a long day couldn't thought of it before lol