General QMAX hole punch
Have used QMax punches for nearly 40 years now (the same ones!). They go from about 1/2" up to 2" or more in metric & imperial sizes.
Excellent tool for making a neat accurate hole in steel sheet up to about 18 swg (1.2mm) normally, thicker if you use cutting lube and go steady.
Typical job, cutting accurate 52mm holes for std. instruments in panels
They are a manual shear tool, male and female parts (cutter and anvil), pulled through the job with a hex socket cap-head bolt. You don't need 100% access to the back of the job, but it's not a completely blind cutting method - if you can put a nut on a bolt throuigh the hole, then you can generally use the QMax.
Here is a hole cut by one for a T25 nylon body breather plug (22.5mm)