How to put a recess into an exsisting metal Chassis

Hi All,

So I am far from being a fabricator, but like to think myself pretty handy with tools. though, I am looking to do something I am not exactly sure how to accomplish with the tools I have.
I want to mount a torroidal transformer into an existing electronics chassis and recess the bolt
here is an example if what I am trying to accomplish, but inside a mild steel metal chassis. seemingly similar thickness to what is shown below

I don't have a hydraulic press, but I have typical tools one would have in ones garage including a drill press sockets etc. Any ideas how I might be able to do this?

 

My unconventional way (not being trained in any metal fabrication) would be to cut a hole to fit the plate perfectly and then weld or rivet a plate on the other side about 1/2 “ larger on each side so you can weld or river it in. Then screw, bolt or rivet the transformer plate to the other.
Larry Cameron

 

what I want to do is actually bend the chassis like the plate is bent in the picture to recess the bolt head. the transformer I am getting does not come with the mounting plate they show. they expect you to drill a hole in your chasses then just let the bolt stick out under your chasses.

 

Counter sink the hole and use a tapered bolt.

 

If you can get to both sides. I would use a big washer on one side and small one on the other side with a bolt, nut and a flat bar.