Let me say first that i'm a noob in electricity. I measured the voltage from my diy microwave-transformer-welder and it was 8. I have no idea how much amps run through it but the fact that it creates lots of sparks and can create welds on metal may suggest that it is a high amount of amps. Is it safe to touch this or do I stick to my gloves?
8 V is too low to send lethal currents through you, unless you implant electrodes under your skin near your heart (don't do that). In fact most authorities round the world reckon that somewhere in the 40 V to 60 V range is safe to touch.
8 V is high enough to send very large currents through metal wires. The heat generated by this could burn you or start fires.
A re-purposed microwave oven transformer is heavy enough to break toes, if dropped.
I seem to recall that anything greater than 20ma thru you can be fatal. At 8 volts, a resistance of 400 ohms would allow 20ma to flow (I=E/R). Dry skin should be much higher than 400 ohms. If, however, your skin is wet or you puncture the epidermis & reach the dermis, you can get a significantly lower resistance. Science experiment: touch a 9 volt battery to your dry fingers and then your tongue. The former should give about 4ua while the latter about 100ua. A lot depends on your body chemistry. Caution is a good habit to establish.